normal physiology. Cheat sheet: briefly, the most important

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normal physiology. Cheat sheet: briefly, the most important

Lecture notes, cheat sheets

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Table of contents

What is normal physiology?
Basic characteristics and laws of excitable tissues
The concept of the state of rest and activity of excitable tissues
Physico-chemical mechanisms of the emergence of the resting potential
Physico-chemical mechanisms of action potential occurrence
Physiology of nerves and nerve fibers. Types of nerve fibers
Laws of conduction of excitation along the nerve fiber
Physical and physiological properties of skeletal, cardiac and smooth muscles
Physiological properties of synapses, their classification
Classification and characteristics of mediators
Basic principles of the functioning of the central nervous system
Structural features, meaning, types of neurons
Reflex arc, its components, types, functions
Functional systems of the body
Coordinating activities
Types of inhibition, interaction of excitation and inhibition processes in the central nervous system
Physiology of the spinal cord
Physiology of the hindbrain and midbrain
Physiology of the diencephalon
Physiology of the reticular formation and limbic system
Physiology of the cerebral cortex
Anatomical and physiological features of the autonomic nervous system
Functions of the sympathetic, parasympathetic and metsympathetic types of the nervous system
General ideas about the endocrine glands
Properties of hormones, the mechanism of their action in the body
Synthesis, secretion and excretion of hormones from the body
Regulation of the activity of the endocrine glands in the body
Anterior pituitary hormones
Middle and posterior pituitary hormones
Hormones of the epiphysis, thymus, parathyroid glands
Thyroid hormones. thyrocalcitonin. Thyroid dysfunction
Pancreatic hormones
Adrenal hormones
Adrenal hormones. Mineralocorticoids. sex hormones
Adrenal medulla hormones and sex hormones
The concept of higher and lower nervous activity
The formation of conditioned reflexes and the mechanism of their inhibition
The concept of the types of the nervous system. Signal system
Components of the circulatory system. Circles of blood circulation. Features of the heart
Properties and structure of the myocardium
Automatic heart
Coronary blood flow, its features
Reflex influences on the activity of the heart
Nervous regulation of the activity of the heart
Humoral regulation of the activity of the heart and vascular tone
Functional system that maintains a constant level of blood pressure
The essence and significance of the processes of respiration
Mechanism of inhalation and exhalation. Breath pattern
Physiological characteristics of the respiratory center, its humoral regulation
Nervous regulation of neuronal activity of the respiratory center
Homeostasis and orguinochemical properties of blood
Blood plasma, its composition
Physiological structure of erythrocytes
The structure of leukocytes and platelets
Functions, significance of the urinary system

1. What is normal physiology?

Normal physiology is a biological discipline that studies:

1) the functions of the whole organism and individual physiological systems (for example, cardiovascular, respiratory);

2) the functions of individual cells and cellular structures that make up organs and tissues (for example, the role of myocytes and myofibrils in the mechanism of muscle contraction);

3) interaction between individual organs of individual physiological systems (for example, the formation of erythrocytes in the red bone marrow);

4) regulation of the activity of internal organs and physiological systems of the body (for example, nervous and humoral).

Physiology is an experimental science. It distinguishes two methods of research - experience and observation. Observation - the study of the behavior of an animal under certain conditions, usually over a long period of time. This makes it possible to describe any function of the body, but makes it difficult to explain the mechanisms of its occurrence. The experience is acute and chronic. The acute experiment is carried out only for a short time, and the animal is in a state of anesthesia. Due to the large blood loss, there is practically no objectivity. The chronic experiment was first introduced by I. P. Pavlov, who proposed to operate on animals (for example, fistula on the stomach of a dog).

A large section of science is devoted to the study of functional and physiological systems. The physiological system is a constant collection of various organs united by some common function.

The formation of such complexes in the body depends on three factors:

1) metabolism;

2) energy exchange;

3) exchange of information.

Functional system - a temporary set of organs that belong to different anatomical and physiological structures, but provide the performance of special forms of physiological activity and certain functions. It has a number of properties such as:

1) self-regulation;

2) dynamism (disintegrates only after the desired result is achieved);

3) the presence of feedback.

Due to the presence of such systems in the body, it can work as a whole.

A special place in normal physiology is given to homeostasis. Homeostasis - a set of biological reactions that ensure the constancy of the internal environment of the body. It is a liquid medium, which is composed of blood, lymph, cerebrospinal fluid, tissue fluid.

2. Basic characteristics and laws of excitable tissues

The main property of any tissue is irritability, that is, the ability of the tissue to change its physiological properties and exhibit functional functions in response to the action of stimuli.

Irritants are factors of the external or internal environment that act on excitable structures. There are two groups of irritants:

1) natural;

2) artificial: physical. Classification of stimuli according to the biological principle:

1) adequate, which, with minimal energy costs, cause tissue excitation in the natural conditions of the organism's existence;

2) inadequate, which cause excitation in the tissues with sufficient strength and prolonged exposure.

The general physiological properties of tissues include:

1) excitability - the ability of living tissue to respond to the action of a sufficiently strong, fast and long-acting stimulus by changing physiological properties and the emergence of an excitation process.

The measure of excitability is the threshold of irritation. The threshold of irritation is the minimum strength of the stimulus that first causes visible responses;

2) conductivity - the ability of a tissue to transmit the resulting excitation due to an electrical signal from the site of irritation along the length of the excitable tissue;

3) refractoriness - a temporary decrease in excitability simultaneously with the excitation that has arisen in the tissue. Refractoriness is absolute;

4) lability - the ability of an excitable tissue to respond to irritation at a certain speed.

The laws establish the dependence of the response of the tissue on the parameters of the stimulus. There are three laws of irritation of excitable tissues:

1) the law of the strength of irritation;

2) the law of duration of irritation;

3) the excitation gradient law.

The law of the strength of irritation establishes the dependence of the response on the strength of the stimulus. This dependence is not the same for individual cells and for the whole tissue. For single cells, addiction is called "all or nothing". The nature of the response depends on the sufficient threshold value of the stimulus.

The law of duration of stimuli. The response of the tissue depends on the duration of the stimulation, but is carried out within certain limits and is directly proportional.

The excitation gradient law. The gradient is the steepness of the increase in irritation. The tissue response depends up to a certain limit on the stimulation gradient.

3. The concept of the state of rest and activity of excitable tissues

The state of rest in excitable tissues is said to be in the case when the tissue is not affected by an irritant from the external or internal environment. At the same time, a relatively constant metabolic rate is observed.

The main forms of the active state of excitable tissue are excitation and inhibition.

Excitation is an active physiological process that occurs in the tissue under the influence of an irritant, while changing the physiological properties of the tissue. Excitation is characterized by a number of signs:

1) specific features characteristic of a particular type of tissue;

2) non-specific features characteristic of all types of tissues (the permeability of cell membranes, the ratio of ion flows, the charge of the cell membrane change, an action potential arises that changes the level of metabolism, oxygen consumption increases and carbon dioxide emission increases).

According to the nature of the electrical response, there are two forms of excitation:

1) local, non-propagating excitation (local response). It is characterized by:

a) there is no latent period of excitation;

b) occurs under the action of any stimulus;

c) there is no refractoriness;

d) attenuates in space and propagates over short distances;

2) impulse, spreading excitation.

It is characterized by:

a) the presence of a latent period of excitation;

b) the presence of a threshold of irritation;

c) the absence of a gradual character;

d) distribution without decrement;

e) refractoriness (excitability of the tissue decreases).

Inhibition is an active process, occurs when stimuli act on the tissue, manifests itself in the suppression of another excitation.

Inhibition can only develop in the form of a local response.

There are two types of braking:

1) primary, for the occurrence of which the presence of special inhibitory neurons is necessary;

2) secondary, which does not require special brake structures. It arises as a result of a change in the functional activity of ordinary excitable structures.

The processes of excitation and inhibition are closely related, occur simultaneously and are different manifestations of a single process.

4. Physical and chemical mechanisms of the emergence of the resting potential

Membrane potential (or resting potential) is the potential difference between the outer and inner surface of the membrane in a state of relative physiological rest. The resting potential arises as a result of two reasons:

1) uneven distribution of ions on both sides of the membrane;

2) selective permeability of the membrane for ions. At rest, the membrane is not equally permeable to different ions. The cell membrane is permeable to K ions, slightly permeable to Na ions, and impermeable to organic substances.

These two factors create conditions for the movement of ions. This movement is carried out without energy expenditure by passive transport - diffusion as a result of the difference in ion concentration. K ions leave the cell and increase the positive charge on the outer surface of the membrane, Cl ions passively pass into the cell, which leads to an increase in the positive charge on the outer surface of the cell. Na ions accumulate on the outer surface of the membrane and increase its positive charge. Organic compounds remain inside the cell. As a result of this movement, the outer surface of the membrane is charged positively, while the inner surface is negatively charged. The inner surface of the membrane may not be absolutely negatively charged, but it is always negatively charged with respect to the outer one. This state of the cell membrane is called the state of polarization. The movement of ions continues until the potential difference across the membrane is balanced, i.e., electrochemical equilibrium occurs. The moment of equilibrium depends on two forces:

1) diffusion forces;

2) forces of electrostatic interaction. The value of electrochemical equilibrium:

1) maintenance of ionic asymmetry;

2) maintaining the value of the membrane potential at a constant level.

The diffusion force (difference in ion concentration) and the force of electrostatic interaction are involved in the occurrence of the membrane potential, therefore the membrane potential is called concentration-electrochemical.

To maintain ionic asymmetry, electrochemical equilibrium is not enough. The cell has another mechanism - the sodium-potassium pump. The sodium-potassium pump is a mechanism for ensuring active transport of ions. The cell membrane has a system of carriers, each of which binds the three Na ions that are inside the cell and brings them out. From the outside, the carrier binds to two K ions located outside the cell and transfers them to the cytoplasm. Energy is taken from the breakdown of ATP.

5. Physico-chemical mechanisms of action potential occurrence

An action potential is a shift in the membrane potential that occurs in the tissue under the action of a threshold and suprathreshold stimulus, which is accompanied by a recharge of the cell membrane.

Under the action of a threshold or suprathreshold stimulus, the permeability of the cell membrane for ions changes to varying degrees. For Na ions, it increases and the gradient develops slowly. As a result, the movement of Na ions occurs inside the cell, K ions move out of the cell, which leads to a recharge of the cell membrane. The outer surface of the membrane is negatively charged, while the inner surface is positive.

Action potential components:

1) local response;

2) high-voltage peak potential (spike);

3) trace vibrations.

Na ions enter the cell by simple diffusion without energy expenditure. Having reached the threshold strength, the membrane potential decreases to a critical level of depolarization (approximately 50 mV). The critical level of depolarization is the number of millivolts by which the membrane potential must decrease in order for an avalanche-like flow of Na ions into the cell to occur.

High voltage peak potential (spike).

The action potential peak is a constant component of the action potential. It consists of two phases:

1) ascending part - phases of depolarization;

2) descending part - phases of repolarization.

An avalanche-like flow of Na ions into the cell leads to a change in the potential on the cell membrane. The more Na ions enter the cell, the more the membrane depolarizes, the more activation gates open. The appearance of a charge with the opposite sign is called the inversion of the membrane potential. The movement of Na ions into the cell continues until the moment of electrochemical equilibrium for the Na ion. The amplitude of the action potential does not depend on the strength of the stimulus, it depends on the concentration of Na ions and on the degree of permeability of the membrane to Na ions. The descending phase (repolarization phase) returns the membrane charge to its original sign. When the electrochemical equilibrium for Na ions is reached, the activation gate is inactivated, the permeability to Na ions decreases, and the permeability to K ions increases. The membrane potential is not completely restored.

In the process of reduction reactions, trace potentials are recorded on the cell membrane - positive and negative.

6. Physiology of nerves and nerve fibers. Types of nerve fibers

Physiological properties of nerve fibers:

1) excitability - the ability to come into a state of excitement in response to irritation;

2) conductivity - the ability to transmit nerve excitation in the form of an action potential from the site of irritation along the entire length;

3) refractoriness (stability) - the property of temporarily sharply reducing excitability in the process of excitation.

Nervous tissue has the shortest refractory period. The value of refractoriness is to protect the tissue from overexcitation, to carry out a response to a biologically significant stimulus;

4) lability - the ability to respond to irritation at a certain speed. Lability is characterized by the maximum number of excitation impulses for a certain period of time (1 s) in exact accordance with the rhythm of the applied stimuli.

Nerve fibers are not independent structural elements of the nervous tissue, they are a complex formation, including the following elements:

1) processes of nerve cells - axial cylinders;

2) glial cells;

3) connective tissue (basal) plate. The main function of nerve fibers is to conduct

nerve impulses. According to the structural features and functions, nerve fibers are divided into two types: unmyelinated and myelinated.

Unmyelinated nerve fibers do not have a myelin sheath. Their diameter is 5-7 microns, the speed of impulse conduction is 1-2 m/s. Myelin fibers consist of an axial cylinder covered by a myelin sheath formed by Schwann cells. The axial cylinder has a membrane and oxo-plasma. The myelin sheath consists of 80% lipids with high ohmic resistance and 20% protein. The myelin sheath does not completely cover the axial cylinder, but is interrupted and leaves open areas of the axial cylinder, which are called nodal interceptions (Ran-vier interceptions). The length of the sections between the intercepts is different and depends on the thickness of the nerve fiber: the thicker it is, the longer the distance between the intercepts.

Depending on the speed of conduction of excitation, nerve fibers are divided into three types: A, B, C.

Type A fibers have the highest excitation conduction speed, the excitation conduction speed of which reaches 120 m / s, B has a speed of 3 to 14 m / s, C - from 0,5 to 2 m / s.

The concepts of "nerve fiber" and "nerve" should not be confused. A nerve is a complex formation consisting of a nerve fiber (myelinated or non-myelinated), a loose fibrous connective tissue that forms a nerve sheath.

7. Laws of conduction of excitation along the nerve fiber

The mechanism of conduction of excitation along the nerve fibers depends on their type. There are two types of nerve fibers: myelinated and unmyelinated.

Metabolic processes in unmyelinated fibers do not provide a quick compensation for energy expenditure. The spread of excitation will go with a gradual attenuation - with a decrement. The decremental behavior of excitation is characteristic of a low-organized nervous system. The excitation is propagated by small circular currents that occur inside the fiber or in the liquid surrounding it. A potential difference arises between the excited and unexcited areas, which contributes to the occurrence of circular currents. The current will spread from "+" charge to "-". At the exit point of the circular current, the permeability of the plasma membrane for Na ions increases, resulting in membrane depolarization. Between the newly excited area and the adjacent unexcited potential difference again arises, which leads to the occurrence of circular currents. The excitation gradually covers the neighboring sections of the axial cylinder and thus spreads to the end of the axon.

In myelin fibers, thanks to the perfection of metabolism, excitation passes without fading, without decrement. Due to the large radius of the nerve fiber, due to the myelin sheath, the electric current can enter and leave the fiber only in the area of interception. When irritation is applied, depolarization occurs in the area of intercept A, the adjacent intercept B is polarized at this time. Between the interceptions, a potential difference arises, and circular currents appear. Due to the circular currents, other interceptions are excited, while the excitation spreads in a saltatory, abrupt manner from one interception to another.

There are three laws of conduction of irritation along the nerve fiber.

The law of anatomical and physiological integrity.

Conduction of impulses along the nerve fiber is possible only if its integrity is not violated.

The law of isolated conduction of excitation.

There are a number of features of the spread of excitation in peripheral, pulpy and non-pulmonic nerve fibers.

In peripheral nerve fibers, excitation is transmitted only along the nerve fiber, but is not transmitted to neighboring nerve fibers that are in the same nerve trunk.

In the pulpy nerve fibers, the role of an insulator is performed by the myelin sheath. Due to myelin, the resistivity increases and the electrical capacitance of the shell decreases.

In the non-fleshy nerve fibers, excitation is transmitted in isolation.

The law of bilateral excitation.

The nerve fiber conducts nerve impulses in two directions - centripetally and centrifugally.

8. Physical and physiological properties of skeletal, cardiac and smooth muscles

According to morphological features, three groups of muscles are distinguished:

1) striated muscles (skeletal muscles);

2) smooth muscles;

3) cardiac muscle (or myocardium).

Functions of the striated muscles:

1) motor (dynamic and static);

2) ensuring breathing;

3) mimic;

4) receptor;

5) depositor;

6) thermoregulatory. Smooth muscle functions:

1) maintaining pressure in hollow organs;

2) regulation of pressure in blood vessels;

3) emptying of hollow organs and promotion of their contents.

The function of the heart muscle is pumping, ensuring the movement of blood through the vessels.

Physiological properties of skeletal muscles:

1) excitability (lower than in the nerve fiber, which is explained by the low value of the membrane potential);

2) low conductivity, about 10-13 m/s;

3) refractoriness (takes a longer period of time than that of a nerve fiber);

4) lability;

5) contractility (the ability to shorten or develop tension).

There are two types of reduction:

a) isotonic contraction (length changes, tone does not change); b) isometric contraction (the tone changes without changing the length of the fiber). There are single and titanic contractions;

6) elasticity.

Physiological features of smooth muscles.

Smooth muscles have the same physiological properties as skeletal muscles, but they also have their own characteristics:

1) unstable membrane potential, which maintains the muscles in a state of constant partial contraction - tone;

2) spontaneous automatic activity;

3) contraction in response to stretching;

4) plasticity (decrease in stretching with increasing stretching);

5) high sensitivity to chemicals. The physiological feature of the heart muscle is its automatism. Excitation occurs periodically under the influence of processes occurring in the muscle itself.

9. Physiological properties of synapses, their classification

A synapse is a structural and functional formation that ensures the transition of excitation or inhibition from the end of a nerve fiber to an innervating cell.

Synapse structure:

1) presynaptic membrane (electrogenic membrane in the axon terminal, forms a synapse on the muscle cell);

2) postsynaptic membrane (electrogenic membrane of the innervated cell on which the synapse is formed);

3) synaptic cleft (the space between the presynaptic and postsynaptic membranes is filled with a fluid that resembles blood plasma in composition).

There are several classifications of synapses.

1. By localization:

1) central synapses;

2) peripheral synapses.

Central synapses lie within the central nervous system and are also located in the ganglia of the autonomic nervous system.

There are several types of peripheral synapses:

1) myoneural;

2) neuro-epithelial.

2. Functional classification of synapses:

1) excitatory synapses;

2) inhibitory synapses.

3. According to the mechanisms of excitation transmission in synapses:

1) chemical;

2) electrical.

The transfer of excitation is carried out with the help of mediators. There are several types of chemical synapses:

1) cholinergic. In them, the transfer of excitation occurs with the help of acetylcholine;

2) adrenergic. In them, the transfer of excitation occurs with the help of three catecholamines;

3) dopaminergic. They transmit excitation with the help of dopamine;

4) histaminergic. In them, the transfer of excitation occurs with the help of histamine;

5) GABAergic. In them, excitation is transferred with the help of gamma-aminobutyric acid, i.e., the process of inhibition develops.

Synapses have a number of physiological properties:

1) the valve property of synapses, i.e., the ability to transmit excitation in only one direction from the presynaptic membrane to the postsynaptic one;

2) the property of synaptic delay, due to the fact that the rate of transmission of excitation is reduced;

3) the property of potentiation (each subsequent impulse will be conducted with a smaller postsynaptic delay);

4) low lability of the synapse (100-150 impulses per second).

10. Mechanisms of excitation transmission in synapses on the example of a myoneural synapse and its structure

Mioneural (neuromuscular) synapse - formed by the axon of a motor neuron and a muscle cell.

The nerve impulse originates in the trigger zone of the neuron, travels along the axon to the innervated muscle, reaches the axon terminal, and at the same time depolarizes the presynaptic membrane.

After that, sodium and calcium channels open, and Ca ions from the environment surrounding the synapse enter the axon terminal. In this process, the Brownian movement of the vesicles is ordered towards the presynaptic membrane. Ca ions stimulate the movement of vesicles. Upon reaching the presynaptic membrane, the vesicles rupture and release acetylcholine (4 Ca ions release 1 quantum of acetylcholine). The synaptic cleft is filled with a fluid that resembles blood plasma in composition; diffusion of ACh from the presynaptic membrane to the postsynaptic membrane occurs through it, but its rate is very low. In addition, diffusion is also possible along the fibrous filaments that are located in the synaptic cleft. After diffusion, ACh begins to interact with chemoreceptors (ChR) and cholinesterase (ChE) located on the postsynaptic membrane.

The cholinergic receptor performs a receptor function, and cholinesterase performs an enzymatic function. On the postsynaptic membrane they are located as follows:

XP-XE-XP-XE-XP-XE.

XP + AX \uXNUMXd MECP - miniature potentials of the end plate.

Then the MECP is summed. As a result of summation, an EPSP is formed - an excitatory postsynaptic potential. The postsynaptic membrane is negatively charged due to EPSP, and in the area where there is no synapse (muscle fiber), the charge is positive. A potential difference arises, an action potential is formed, which moves along the conduction system of the muscle fiber.

ChE + ACh = destruction of ACh to choline and acetic acid.

In a state of relative physiological rest, the synapse is in background bioelectrical activity. Its significance lies in the fact that it increases the readiness of the synapse to conduct a nerve impulse, thereby greatly facilitating the transmission of nerve excitation through the synapse. At rest, 1-2 vesicles in the axon terminal may accidentally approach the presynaptic membrane, as a result of which they will come into contact with it. The vesicle bursts on contact with the presynaptic membrane, and its contents in the form of 1 quantum of ACh enter the synaptic cleft, falling on the postsynaptic membrane, where MPN will be formed.

11. Classification and characteristics of mediators

A mediator is a group of chemicals that takes part in the transfer of excitation or inhibition in chemical synapses from the presynaptic to the postsynaptic membrane. Criteria by which a substance is classified as a mediator:

1) the substance must be released on the presynaptic membrane, the axon terminal;

2) in the structures of the synapse, there must be enzymes that promote the synthesis and breakdown of the mediator, and there must also be receptors on the postsynaptic membrane;

3) a substance that claims to be a mediator must transmit excitation from the presynaptic membrane to the postsynaptic membrane.

Classification of mediators:

1) chemical, based on the structure of the mediator;

2) functional, based on the function of the mediator. Chemical classification.

1. Esters - acetylcholine (AH).

2. Biogenic amines:

1) catecholamines (dopamine, norepinephrine (HA), adrenaline (A));

2) serotonin;

3) histamine.

3. Amino acids:

1) gamma-aminobutyric acid (GABA);

2) glutamic acid;

3) glycine;

4) arginine.

4. Peptides:

1) opioid peptides: a) methenkephalin;

b) enkephalins;

c) leuenkephalins;

2) substance "P";

3) vasoactive intestinal peptide;

4) somatostatin.

5. Purine compounds: ATP.

6. Substances with a minimum molecular weight:

1) NO;

2) CO.

Functional classification.

1. Excitatory mediators:

1) AH;

2) glutamic acid;

3) aspartic acid.

2. Inhibitory mediators that cause hyperpolarization of the postsynaptic membrane, after which an inhibitory postsynaptic potential arises, which generates the process of inhibition:

1) GABA;

2) glycine;

3) substance "P";

4) dopamine;

5) serotonin;

6) ATP.

12. Basic principles of the functioning of the central nervous system

The main principle of the functioning of the central nervous system is the process of regulation, control of physiological functions, which are aimed at maintaining the constancy of the properties and composition of the internal environment of the body. The central nervous system ensures the optimal relationship of the organism with the environment, stability, integrity, and the optimal level of vital activity of the organism.

There are two main types of regulation: humoral and nervous.

The humoral control process involves a change in the physiological activity of the body under the influence of chemicals that are delivered by the liquid media of the body. The source of information transfer is chemical substances - utilizons, metabolic products (carbon dioxide, glucose, fatty acids), informons, hormones of endocrine glands, local or tissue hormones.

The nervous process of regulation provides for the control of changes in physiological functions along nerve fibers with the help of an excitation potential under the influence of information transmission.

Characteristics:

1) is a later product of evolution;

2) provides fast handling;

3) has an exact addressee of the impact;

4) implements an economical way of regulation;

5) provides high reliability of information transmission.

In the body, the nervous and humoral mechanisms work as a single system of neurohumoral control. This is a combined form, where two control mechanisms are used simultaneously, they are interconnected and interdependent.

The nervous system is a collection of nerve cells, or neurons.

According to localization, they distinguish:

1) the central section - the brain and spinal cord;

2) peripheral - processes of nerve cells of the brain and spinal cord.

According to functional features, they distinguish:

1) somatic department that regulates motor activity;

2) vegetative, regulating the activity of internal organs, endocrine glands, blood vessels, trophic innervation of muscles and the central nervous system itself.

Functions of the nervous system:

1) integrative-coordination function. Provides the functions of various organs and physiological systems, coordinates their activities with each other;

2) ensuring close connections of the human body with the environment at the biological and social levels;

3) regulation of the level of metabolic processes in various organs and tissues, as well as in itself;

4) ensuring mental activity by the higher departments of the central nervous system.

13. Structural features, meaning, types of neurons

The structural and functional unit of the nervous tissue is the nerve cell - the neuron.

A neuron is a specialized cell that is able to receive, encode, transmit and store information, establish contacts with other neurons, and organize the body's response to irritation.

Functionally in a neuron, there are:

1) the receptive part (the dendrites and the membrane of the soma of the neuron);

2) integrative part (soma with axon hillock);

3) the transmitting part (axon hillock with axon). Receptive part.

Dendrites are the main perceiving field of the neuron.

The dendrite membrane is able to respond to neurotransmitters. The neuron has several branching dendrites.

The soma membrane of a neuron is 6 nm thick and consists of two layers of lipid molecules. Proteins are embedded in the lipid bilayer of the membrane, which perform several functions:

1) pump proteins - move ions and molecules in the cell against the concentration gradient;

2) proteins built into the channels provide selective membrane permeability;

3) receptor proteins recognize the desired molecules and fix them on the membrane;

4) enzymes facilitate the flow of a chemical reaction on the surface of the neuron.

integrative part. The axon hillock is the exit point of the axon from the neuron.

The soma of a neuron (the body of a neuron) performs, along with an informational and trophic function, regarding its processes and synapses. The soma provides the growth of dendrites and axons.

Transmitting part.

Axon - an outgrowth of the cytoplasm, adapted to carry information that is collected by dendrites and processed in a neuron. The axon of a dendritic cell has a constant diameter and is covered with a myelin sheath, which is formed from glia; the axon has branched endings that contain mitochondria and secretory formations.

Types of neurons:

1) by localization:

a) central (brain and spinal cord);

b) peripheral (cerebral ganglia, cranial nerves);

2) depending on the function:

a) afferent;

b) insert;

c) efferent;

3) depending on the functions:

a) exciting;

b) inhibitory.

14. Reflex arc, its components, types, functions

The activity of the body is a natural reflex reaction to a stimulus. Reflex - the reaction of the body to irritation of receptors, which is carried out with the participation of the central nervous system. The structural basis of the reflex is the reflex arc.

A reflex arc is a series-connected chain of nerve cells that ensures the implementation of a reaction, a response to irritation.

The reflex arc consists of six components: receptors, afferent pathway, reflex center, efferent pathway, effector (working organ), feedback.

Reflex arcs can be of two types:

1) simple - monosynaptic reflex arcs (reflex arc of the tendon reflex), consisting of 2 neurons (receptor (afferent) and effector), there is 1 synapse between them;

2) complex - polysynaptic reflex arcs. They include 3 neurons (there may be more) - receptor, one or more intercalary and effector.

The feedback loop establishes a connection between the realized result of the reflex reaction and the nerve center that issues executive commands. With the help of this component, the open reflex arc is transformed into a closed one.

Features of a simple monosynaptic reflex arc:

1) geographically close receptor and effector;

2) the reflex arc is two-neuron, monosynaptic;

3) nerve fibers of group Aa (70-120 m/s);

4) short reflex time;

5) muscles that contract as a single muscle contraction.

Features of a complex monosynaptic reflex arc:

1) territorially separated receptor and effector;

2) the receptor arc is three-neuronal;

3) the presence of nerve fibers of groups C and B;

4) muscle contraction by the type of tetanus. Features of the autonomic reflex:

1) the intercalary neuron is located in the lateral horns;

2) the preganglionic nerve path begins from the lateral horns, after the ganglion - the postganglionic one;

3) the efferent path of the reflex of the autonomic neural arch is interrupted by the autonomic ganglion, in which the efferent neuron lies.

The difference between the sympathetic neural arch and the parasympathetic one: in the sympathetic neural arch, the preganglionic path is short, since the autonomic ganglion lies closer to the spinal cord, and the postganglionic path is long.

In the parasympathetic arch, the opposite is true: the preganglionic path is long, since the ganglion lies close to the organ or in the organ itself, and the postganglionic path is short.

15. Functional systems of the body

A functional system is a temporary functional association of the nerve centers of various organs and systems of the body in order to achieve a final beneficial result.

A useful result is a self-forming factor of the nervous system.

There are several groups of end useful results:

1) metabolic - a consequence of metabolic processes at the molecular level, which create substances and end products necessary for life;

2) homeostatic - the constancy of indicators of the state and composition of the body's environments;

3) behavioral - the result of a biological need;

4) social - satisfaction of social and spiritual needs.

The functional system includes various organs and systems, each of which takes an active part in achieving a useful result.

The functional system, according to P.K. Anokhin, includes five main components:

1) a useful adaptive result - something for which a functional system is created;

2) control apparatus - a group of nerve cells in which a model of the future result is formed;

3) reverse afferentation - secondary afferent nerve impulses that go to the acceptor of the result of the action to assess the final result;

4) control apparatus - a functional association of nerve centers with the endocrine system;

5) executive components are the organs and physiological systems of the body. Consists of four components:

a) internal organs;

b) endocrine glands;

c) skeletal muscles;

d) behavioral responses. Functional system properties:

1) dynamism. The functional system may include additional organs and systems, depending on the complexity of the situation;

2) the ability to self-regulation. When the controlled value or the final useful result deviates from the optimal value, a series of spontaneous complex reactions occur, which returns the indicators to the optimal level. Self-regulation is carried out in the presence of feedback.

Several functional systems work simultaneously in the body. They are in continuous interaction, which is subject to certain principles:

1) the principle of the system of genesis;

2) the principle of multiply connected interaction;

3) the principle of hierarchy;

4) the principle of consistent dynamic interaction.

16. Coordination activities

Coordination activity (CA) of the CNS is a coordinated work of CNS neurons based on the interaction of neurons with each other.

CD functions:

1) provides a clear performance of certain functions, reflexes;

2) ensures the consistent inclusion in the work of various nerve centers to ensure complex forms of activity;

3) ensures the coordinated work of various nerve centers.

Basic principles of CNS CD and their neural mechanisms.

1. The principle of irradiation. When small groups of neurons are excited, the excitation spreads to a significant number of neurons.

2. The principle of convergence. When a large number of neurons are excited, the excitation can converge to one group of nerve cells.

3. The principle of reciprocity - the coordinated work of the nerve centers, especially in opposite reflexes (flexion, extension, etc.).

4. The principle of dominance. Dominant - the dominant focus of excitation in the central nervous system at the moment. The dominant underlies the formation of a conditioned reflex.

5. The principle of feedback. There are two types of feedback:

1) positive feedback, causing an increase in the response from the nervous system.

Underlies a vicious circle that leads to the development of diseases;

2) negative feedback, which reduces the activity of CNS neurons and the response. Underlies self-regulation.

6. The principle of subordination. In the CNS, there is a certain subordination of departments to each other, the highest department is the cerebral cortex.

7. The principle of interaction between the processes of excitation and inhibition. The central nervous system coordinates the processes of excitation and inhibition: both processes are capable of convergence, the process of excitation and, to a lesser extent, inhibition, are capable of irradiation. Inhibition and excitation are connected by inductive relationships. The process of excitation induces inhibition, and vice versa. There are two types of induction:

1) consistent. The process of excitation and inhibition replace each other in time;

2) mutual. At the same time, there are two processes - excitation and inhibition.

The coordination activity of the central nervous system provides a clear interaction between individual nerve cells and individual groups of nerve cells.

17. Types of inhibition, the interaction of the processes of excitation and inhibition in the central nervous system

Inhibition is an active process that occurs under the action of stimuli on the tissue, manifests itself in the suppression of another excitation, there is no functional administration of the tissue.

Inhibition can only develop in the form of a local response.

There are two types of braking:

1) primary. For its occurrence, the presence of special inhibitory neurons is necessary. Inhibition occurs primarily without prior excitation under the influence of an inhibitory mediator. There are two types of primary inhibition:

a) presynaptic in the axo-axonal synapse;

b) postsynaptic in the axodendric synapse.

2) secondary. It does not require special inhibitory structures, it arises as a result of a change in the functional activity of ordinary excitable structures, it is always associated with the process of excitation. Types of secondary braking:

a) beyond, arising from a large flow of information entering the cell. The flow of information lies outside the neuron's performance;

b) pessimal, arising at a high frequency of irritation;

c) parabiotic, arising from strong and long-acting irritation;

d) inhibition following excitation, resulting from a decrease in the functional state of neurons after excitation;

e) braking according to the principle of negative induction;

f) inhibition of conditioned reflexes.

The processes of excitation and inhibition are closely related, occur simultaneously and are different manifestations of a single process.

Inhibition underlies the coordination of movements, protects the central neurons from overexcitation. Inhibition in the central nervous system can occur when nerve impulses of various strengths from several stimuli simultaneously enter the spinal cord. Stronger stimulation inhibits the reflexes that should have come in response to weaker ones.

In 1862, I. M. Sechenov proved in his experiment that irritation of the frog's optic tubercles by a crystal of sodium chloride causes inhibition of spinal cord reflexes. After elimination of the stimulus, the reflex activity of the spinal cord was restored.

The result of this experiment allowed I. M. Secheny to conclude that in the central nervous system, along with the process of excitation, a process of inhibition develops, which is capable of inhibiting the reflex acts of the body.

18. Physiology of the spinal cord

The spinal cord is the most ancient formation of the CNS. A characteristic feature of the structure is segmentation.

The neurons of the spinal cord form its gray matter in the form of anterior and posterior horns. They perform a reflex function of the spinal cord.

The posterior horns contain neurons (interneurons) that transmit impulses to the overlying centers, to the symmetrical structures of the opposite side, to the anterior horns of the spinal cord. The posterior horns contain afferent neurons that respond to pain, temperature, tactile, vibration, and proprioceptive stimuli.

The anterior horns contain neurons (motoneurons) that give axons to the muscles, they are efferent.

All descending pathways of the CNS for motor reactions terminate in the anterior horns.

In the lateral horns of the cervical and two lumbar segments there are neurons of the sympathetic division of the autonomic nervous system, in the second-fourth segments - of the parasympathetic.

The spinal cord contains many intercalary neurons that provide communication with the segments and with the overlying parts of the CNS. They include associative neurons - neurons of the spinal cord's own apparatus, they establish connections within and between segments. The white matter of the spinal cord is formed by myelin fibers (short and long) and performs a conductive role. Short fibers connect neurons of one or different segments of the spinal cord.

Long fibers (projection) form the pathways of the spinal cord. They form ascending pathways to the brain and descending pathways from the brain.

The spinal cord performs reflex and conduction functions.

The reflex function allows you to realize all the motor reflexes of the body, reflexes of internal organs, thermoregulation, etc. Reflex reactions depend on the location, strength of the stimulus, the area of the reflexogenic zone, the speed of the impulse through the fibers, and the influence of the brain.

Reflexes are divided into:

1) exteroceptive (occur when irritated by environmental agents of sensory stimuli);

2) interoceptive: viscero-visceral, visceral-muscular;

3) proprioceptive (own) reflexes from the muscle itself and its associated formations. They have a monosynaptic reflex arc. Proprioceptive reflexes regulate motor activity due to tendon and postural reflexes;

4) postural reflexes (occur when the vestibular receptors are excited when the speed of movement and the position of the head relative to the body change, which leads to a redistribution of muscle tone).

19. Physiology of the hindbrain and midbrain

Structural formations of the hindbrain.

1. V-XII pair of cranial nerves.

2. Vestibular nuclei.

3. Kernels of the reticular formation.

The main functions of the hindbrain are conductive and reflex.

Descending paths pass through the hindbrain (corticospinal and extrapyramidal), ascending - reticulo- and vestibulospinal, responsible for the redistribution of muscle tone and maintaining body posture.

The reflex function provides:

1) protective reflexes (lacrimation, blinking, coughing, vomiting, sneezing);

2) the speech center provides voice reflexes, the nuclei of the X, XII, VII cranial nerves, the respiratory center regulates the flow of air, the cerebral cortex - the center of speech;

3) posture maintenance reflexes (labyrinth reflexes). Static reflexes maintain muscle tone to maintain body posture, statokinetic ones redistribute muscle tone to take a pose corresponding to the moment of rectilinear or rotational movement;

4) centers located in the hindbrain regulate the activity of many systems.

The vascular center regulates vascular tone, the respiratory center regulates inhalation and exhalation, the complex food center regulates the secretion of the gastric, intestinal glands, pancreas, liver secretory cells, salivary glands, provides sucking, chewing, swallowing reflexes.

Structural units of the midbrain:

1) tubercles of the quadrigemina;

2) red core;

3) black core;

4) nuclei of the III-IV pair of cranial nerves. The tubercles of the quadrigemina perform afferent

function, the remaining formations - efferent.

The tubercles of the quadrigemina closely interact with the nuclei of III-IV pairs of cranial nerves, the red nucleus, with the optic tract.

Due to this interaction, the anterior tubercles provide an orienting reflex reaction to light, and the posterior tubercles to sound. Provide vital reflexes.

The anterior tubercles with the nuclei of the III-IV cranial nerves provide a convergence reaction for the movement of the eyeballs.

The red nucleus takes part in the regulation of the redistribution of muscle tone, in restoring the posture of the body, maintaining balance, and preparing skeletal muscles for voluntary and involuntary movements.

The substantia nigra of the brain coordinates the act of swallowing and chewing, breathing, and the level of blood pressure.

20. Physiology of the diencephalon

The diencephalon consists of the thalamus and hypothalamus, they connect the brain stem with the cerebral cortex.

The thalamus is a paired formation, the largest accumulation of gray matter in the diencephalon.

Topographically, the anterior, middle, posterior, medial and lateral groups of nuclei are distinguished.

By function, they distinguish:

1) specific:

a) switching, relay. They receive primary information from various receptors. The nerve impulse along the thalamocortical tract goes to a strictly limited area of the cerebral cortex (primary projection zones), due to this, specific sensations arise. The nuclei of the ventrabasal complex receive an impulse from skin receptors, tendon proprioceptors, and ligaments.

The impulse is sent to the sensorimotor zone, the body orientation in space is regulated;

b) associative (internal) nuclei. The primary impulse comes from the relay nuclei, is processed (an integrative function is carried out), transmitted to the associative zones of the cerebral cortex;

2) non-specific nuclei. This is a non-specific way of transmitting impulses to the cerebral cortex, the frequency of the biopotential changes (modeling function);

3) motor nuclei involved in the regulation of motor activity.

The hypothalamus is located at the bottom and sides of the third ventricle of the brain. Structures: gray tubercle, funnel, mastoid bodies. Zones: hypophysiotropic (preoptic and anterior nuclei), medial (middle nuclei), lateral (outer, posterior nuclei).

Physiological role - the highest subcortical integrative center of the autonomic nervous system, which has an effect on:

1) thermoregulation. The anterior nuclei are the center of body output. The posterior nuclei are the center of heat production and the preservation of heat when the temperature drops;

2) pituitary. Liberins promote the secretion of hormones of the anterior pituitary gland, statins inhibit it;

3) fat metabolism. Irritation of the lateral (nutrition center) nuclei and ventromedial (satiation center) nuclei leads to obesity, inhibition leads to cachexia;

4) carbohydrate metabolism. Irritation of the anterior nuclei leads to hypoglycemia, the posterior nuclei to hyperglycemia;

5) the cardiovascular system. Irritation of the anterior nuclei has an inhibitory effect, the posterior nuclei - an activating one;

6) motor and secretory functions of the gastrointestinal tract. Irritation of the anterior nuclei increases motility and secretory function of the gastrointestinal tract, the posterior nuclei - inhibits sexual function;

7) behavioral responses. Irritation of the starting emotional zone (anterior nuclei) causes a feeling of joy, satisfaction, erotic feelings.

21. Physiology of the reticular formation and limbic system

The reticular formation of the brain stem is an accumulation of polymorphic neurons along the brain stem.

Physiological feature of neurons of the reticular formation:

1) spontaneous bioelectrical activity;

2) sufficiently high excitability of neurons;

3) high sensitivity to biologically active substances.

The reticular formation has wide bilateral connections with all parts of the nervous system; according to its functional significance and morphology, it is divided into two parts:

1) rastral (ascending) department - reticular formation of the diencephalon;

2) caudal (descending) - the reticular formation of the hindbrain, midbrain, bridge.

The physiological role of the reticular formation is the activation and inhibition of brain structures.

The limbic system is a collection of nuclei and nerve tracts.

Structural units of the limbic system:

1) olfactory bulb;

2) olfactory tubercle;

3) transparent partition;

4) hippocampus;

5) parahippocampal gyrus;

6) almond-shaped nuclei;

7) piriform gyrus;

8) dentate fascia;

9) cingulate gyrus.

The main functions of the limbic system:

1) participation in the formation of food, sexual, defensive instincts;

2) regulation of vegetative-visceral functions;

3) the formation of social behavior;

4) participation in the formation of the mechanisms of long-term and short-term memory;

5) performance of the olfactory function. Significant formations of the limbic system are:

1) hippocampus. Its damage leads to a violation of the process of memorization, information processing, a decrease in emotional activity, initiative, a slowdown in the speed of nervous processes, irritation - to an increase in aggression, defensive reactions, and motor function;

2) almond-shaped nuclei. Their damage leads to the disappearance of fear, inability to aggression, hypersexuality, reactions of caring for offspring, irritation - to a parasympathetic effect on the respiratory and cardiovascular, digestive systems;

3) olfactory bulb, olfactory tubercle.

22. Physiology of the cerebral cortex

The highest division of the CNS is the cerebral cortex.

The cerebral cortex has a five-, six-layer structure. Neurons are represented by sensory, motor (Betz cells), interneurons (inhibitory and excitatory neurons).

The columns of the cerebral hemispheres are the functional units of the cortex, divided into micromodules, which have homogeneous neurons.

The main functions of the cerebral cortex:

1) integration (thinking, consciousness, speech);

2) ensuring the connection of the organism with the external environment, its adaptation to its changes;

3) clarification of the interaction between the body and systems within the body;

4) coordination of movements.

These functions are provided by corrective, triggering, integrative mechanisms.

I. P. Pavlov, creating the doctrine of analyzers, singled out three sections: peripheral (receptor), conductive (three-neural pathway for transmitting impulses from receptors), brain (certain areas of the cerebral cortex, where the processing of the nerve impulse, which acquires new quality). The brain section consists of the analyzer nuclei and scattered elements.

According to modern ideas about the localization of functions, three types of fields arise during the passage of an impulse in the cerebral cortex.

1. The primary projection zone lies in the region of the central section of the analyzer nuclei, where the electrical response (evoked potential) first appeared, disturbances in the region of the central nuclei lead to disturbance of sensations.

2. The secondary zone lies in the environment of the nucleus, is not associated with receptors, the impulse comes through the intercalary neurons from the primary projection zone. Here, a relationship is established between phenomena and their qualities, violations lead to a violation of perceptions (generalized reflections).

3. The tertiary (associative) zone has multisensory neurons. The information has been revised to meaningful. The system is capable of plastic restructuring, long-term storage of traces of sensory action. In case of violation, the form of abstract reflection of reality, speech, purposeful behavior suffer.

Collaboration of the cerebral hemispheres and their asymmetry.

There are morphological prerequisites for the joint work of the hemispheres. The corpus callosum provides a horizontal connection with the subcortical formations and the reticular formation of the brain stem. Thus, the friendly work of the hemispheres and reciprocal innervation are carried out during joint work. functional asymmetry. Speech, motor, visual and auditory functions dominate in the left hemisphere. The mental type of the nervous system is left hemisphere, and the artistic type is right hemisphere.

23. Anatomical and physiological features of the autonomic nervous system

The concept of the autonomic nervous system was first introduced in 1801 by the French physician A. Besha. This department of the central nervous system provides extraorganic and intraorganic regulation of body functions and includes three components:

1) sympathetic;

2) parasympathetic;

3) metsympathetic. Anatomical properties

1. Three-component focal arrangement of nerve centers. The lowest level of the sympathetic section is represented by the lateral horns from the VII cervical to III-IV lumbar vertebrae, and the parasympathetic - by the sacral segments and the brain stem. The higher subcortical centers are located on the border of the nuclei of the hypothalamus (the sympathetic division is the posterior group, and the parasympathetic division is the anterior one). The cortical level lies in the region of the sixth-eighth Brodmann fields (motosensory zone), in which point localization of incoming nerve impulses is achieved. Due to the presence of such a structure of the autonomic nervous system, the work of internal organs does not reach the threshold of our consciousness.

2. The presence of autonomic ganglia. In the sympathetic department, they are located either on both sides along the spine, or are part of the plexus. Thus, the arch has a short preganglionic and a long postganglionic path. The neurons of the parasympathetic division are located near the working organ or in its wall, so the arc has a long preganglionic and short postganglionic path.

3. Effetor fibers belong to group B and C. Physiological properties

1. Features of the functioning of the autonomic ganglia. The presence of the phenomenon of multiplication (the simultaneous occurrence of two opposite processes - divergence and convergence). Divergence - the divergence of nerve impulses from the body of one neuron to several postganglionic fibers of another. Convergence - convergence on the body of each postganglionic neuron of impulses from several preganglionic ones. An increase in the duration of the postsynaptic potential, the presence of trace hyperpolarization and synoptic delay contribute to the transmission of excitation. However, the impulses are partially extinguished or completely blocked in the autonomic ganglia. Due to this property, they are called peripheral nerve centers, and the autonomic nervous system is called autonomous.

2. Features of nerve fibers. Since the efferent pathway of the sympathetic division is represented by preganglionic fibers, and the parasympathetic pathway is represented by postganglionic fibers, the speed of impulse transmission is higher in the parasympathetic nervous system.

24. Functions of the sympathetic, parasympathetic and metsympathetic types of the nervous system

The sympathetic nervous system innervates all organs and tissues (stimulates the work of the heart, increases the lumen of the respiratory tract, inhibits the secretory, motor and absorption activity of the gastrointestinal tract, etc.). It performs homeostatic and adaptive-trophic functions.

Its homeostatic role is to maintain the constancy of the internal environment of the body in an active state, i.e., the sympathetic nervous system is included in the work only during physical exertion, emotional reactions, stress, pain effects, blood loss.

The adaptive-trophic function is aimed at regulating the intensity of metabolic processes. This ensures the adaptation of the organism to the changing conditions of the environment of existence.

Thus, the sympathetic department begins to act in an active state and ensures the functioning of organs and tissues.

The parasympathetic nervous system is an antagonist of the sympathetic and performs homeostatic and protective functions, regulates the emptying of hollow organs.

The homeostatic role is restorative and operates at rest. This manifests itself in the form of a decrease in the frequency and strength of heart contractions, stimulation of the activity of the gastrointestinal tract with a decrease in blood glucose levels, etc.

All protective reflexes rid the body of foreign particles. For example, coughing clears the throat, sneezing clears the nasal passages, vomiting causes food to be expelled, etc.

Emptying of hollow organs occurs with an increase in the tone of smooth muscles that make up the wall. This leads to the entry of nerve impulses into the central nervous system, where they are processed and sent along the effector path to the sphincters, causing them to relax.

The metsympathetic nervous system is a collection of microganglia located in organ tissue. They consist of three types of nerve cells - afferent, efferent and intercalary, therefore, they perform the following functions:

1) provides intraorganic innervation;

2) are an intermediate link between the tissue and the extraorganic nervous system. Under the action of a weak stimulus, the met-sympathetic department is activated, and everything is decided at the local level. When strong impulses are received, they are transmitted through the parasympathetic and sympathetic divisions to the central ganglia, where they are processed.

The metsympathetic nervous system regulates the work of smooth muscles that make up most of the organs of the gastrointestinal tract, myocardium, secretory activity, local immunological reactions, and other functions of internal organs.

25. General ideas about the endocrine glands

Endocrine glands are specialized organs that do not have excretory ducts and secrete a secret into the blood, cerebral fluid, and lymph through the intercellular gaps.

The endocrine glands are distinguished by a complex morphological structure with good blood supply, located in various parts of the body. A feature of the vessels that feed the glands is their high permeability, which contributes to the easy penetration of hormones into the intercellular gaps, and vice versa. The glands are rich in receptors and are innervated by the autonomic nervous system.

There are two groups of endocrine glands:

1) carrying out external and internal secretion with a mixed function (i.e., these are the sex glands, pancreas);

2) carrying out only internal secretion. A common function for all glands is the production of hormones.

The endocrine function is a complex system consisting of a number of interrelated and finely balanced components. This system is specific and includes:

1) synthesis and secretion of hormones;

2) transport of hormones into the blood;

3) metabolism of hormones and their excretion;

4) the interaction of the hormone with tissues;

5) processes of regulation of gland functions. Hormones are chemical compounds that have high biological activity and, in small quantities, a significant physiological effect.

Hormones are transported by the blood to organs and tissues, while only a small part of them circulates in a free active form. The main part is in the blood in a bound form in the form of reversible complexes with blood plasma proteins and formed elements. These two forms are in equilibrium with each other, with the equilibrium at rest shifted significantly towards reversible complexes. The components of the complex of hormones with proteins are interconnected by non-covalent, weak bonds.

Hormones that are not associated with blood transport proteins have direct access to cells and tissues. In parallel, two processes occur: the implementation of the hormonal effect and the metabolic breakdown of hormones. Metabolic inactivation is important in maintaining hormonal homeostasis.

According to their chemical nature, hormones are divided into three groups:

1) steroids;

2) polypeptides and proteins with and without a carbohydrate component;

3) amino acids and their derivatives.

Hormones must be constantly synthesized and secreted, act quickly and be inactivated at high speed.

26. Properties of hormones, the mechanism of their action in the body

There are three main properties of hormones:

1) the distant nature of the action (the organs and systems on which the hormone acts are located far from the place of its formation);

2) strict specificity of action;

3) high biological activity.

The action of the hormone on body functions is carried out by two main mechanisms: through the nervous system and humorally, directly on organs and tissues.

Hormones function as chemical messengers that carry information or a signal to a specific location - a target cell that has a highly specialized protein receptor to which the hormone binds.

According to the mechanism of action of cells with hormones, hormones are divided into two types.

The first type (steroids, thyroid hormones) - hormones relatively easily penetrate into the cell through plasma membranes and do not require the action of an intermediary (mediator).

The second type - they do not penetrate well into the cell, act from its surface, require the presence of a mediator, their characteristic feature is quick responses.

In accordance with the two types of hormones, two types of hormonal reception are also distinguished: intracellular (the receptor apparatus is localized inside the cell), membrane (contact) - on its outer surface. Cellular receptors are special sections of the cell membrane that form specific complexes with the hormone. Receptors have certain properties such as:

1) high affinity for a particular hormone;

2) selectivity;

3) limited capacity to the hormone;

4) specificity of localization in the tissue. Binding of hormonal compounds by the receptor is a trigger for the formation and release of mediators inside the cell.

The action of the hormone can be carried out in a more complex way with the participation of the nervous system. Hormones act on interoreceptors that have a specific sensitivity (chemoreceptors in the walls of blood vessels). This is the beginning of a reflex reaction that changes the functional state of the nerve centers.

There are four types of hormone effects on the body:

1) metabolic effect - effect on metabolism;

2) morphogenetic impact - stimulation of formation, differentiation, growth and metamorphosis;

3) triggering impact - influence on the activity of effectors;

4) corrective effect - a change in the intensity of the activity of organs or the whole organism.

27. Synthesis, secretion and excretion of hormones from the body

Biosynthesis of hormones is a chain of biochemical reactions that form the structure of a hormonal molecule. These reactions proceed spontaneously and are genetically fixed in the corresponding endocrine cells.

Genetic control is carried out either at the level of formation of mRNA (messenger RNA) of the hormone itself or its precursors, or at the level of formation of mRNA proteins of enzymes that control the various stages of hormone formation.

Depending on the nature of the hormone being synthesized, there are two types of genetic control of hormonal biogenesis:

1) direct, biosynthesis scheme: "genes - mRNA - pro-hormones - hormones";

2) mediated, scheme: "genes - (mRNA) - enzymes - hormone".

Secretion of hormones - the process of releasing hormones from endocrine cells into the intercellular gaps with their further entry into the blood, lymph. The secretion of the hormone is strictly specific for each endocrine gland.

The secretory process is carried out both at rest and under conditions of stimulation.

The secretion of the hormone occurs impulsively, in separate discrete portions. The impulsive nature of hormonal secretion is explained by the cyclic nature of the processes of biosynthesis, deposition and transport of the hormone.

Secretion and biosynthesis of hormones are closely interconnected with each other. This relationship depends on the chemical nature of the hormone and the characteristics of the secretion mechanism.

There are three mechanisms of secretion:

1) release from cellular secretory granules (secretion of catecholamines and protein-peptide hormones);

2) release from the protein-bound form (secretion of tropic hormones);

3) relatively free diffusion through cell membranes (secretion of steroids).

The degree of connection between the synthesis and secretion of hormones increases from the first type to the third.

Hormones, entering the blood, are transported to organs and tissues. The hormone associated with plasma proteins and formed elements accumulates in the bloodstream, is temporarily switched off from the circle of biological action and metabolic transformations. An inactive hormone is easily activated and gains access to cells and tissues.

In parallel, there are two processes: the implementation of the hormonal effect and metabolic inactivation.

In the process of metabolism, hormones change functionally and structurally. The vast majority of hormones are metabolized, and only a small part (0,5-10%) is excreted unchanged. Metabolic inactivation occurs most intensively in the liver, small intestine and kidneys. Products of hormonal metabolism are actively excreted with urine and bile, bile components are finally excreted by feces through the intestines.

28. Regulation of the activity of the endocrine glands in the body

All processes occurring in the body have specific regulatory mechanisms. One of the levels of regulation is intracellular, acting at the cell level. Like many multistage biochemical reactions, the processes of activity of the endocrine glands are self-regulating to some extent according to the feedback principle. According to this principle, the previous stage of the chain of reactions either inhibits or enhances the subsequent ones.

The primary role in the mechanism of regulation is played by the intercellular systemic control mechanism, which makes the functional activity of the glands dependent on the state of the whole organism.

The systemic mechanism of regulation determines the main physiological role of the endocrine glands - bringing the level and ratio of metabolic processes into line with the needs of the whole organism.

Violation of regulatory processes leads to pathology of the functions of the glands and the whole organism as a whole.

Regulatory mechanisms can be stimulating (facilitating) and inhibitory.

The leading place in the regulation of the endocrine glands belongs to the central nervous system. There are several regulatory mechanisms:

1) nervous. Direct nerve influences play a decisive role in the functioning of the innervated organs (adrenal medulla, neuroendocrine zones of the hypothalamus and epiphysis);

2) neuroendocrine, associated with the activity of the pituitary gland and hypothalamus.

In the hypothalamus, the nerve impulse is transformed into a specific endocrine process, leading to the synthesis of the hormone and its release in special zones of neurovascular contact. There are two types of neuroendocrine reactions:

a) the formation and secretion of releasing factors - the main regulators of the secretion of pituitary hormones (hormones are formed in the small cell nuclei of the hypothalamic region, enter the median eminence, where they accumulate and penetrate the adenohypophysis portal circulation system and regulate their functions);

b) the formation of neurohypophyseal hormones (hormones themselves are formed in the large cell nuclei of the anterior hypothalamus, descend to the posterior lobe, where they are deposited, from there they enter the general circulation system and act on peripheral organs);

3) endocrine (the direct effect of some hormones on the biosynthesis and secretion of others (tropic hormones of the anterior pituitary gland, insulin, somatostatin));

4) neuroendocrine humoral. It is carried out by non-hormonal metabolites that have a regulatory effect on the glands (glucose, amino acids, potassium and sodium ions, prostaglandins).

29. Anterior pituitary hormones

The pituitary gland is called the central gland, since due to its tropic hormones, the activity of other endocrine glands is regulated. The pituitary gland consists of the adenohypophysis (anterior and middle lobes) and the neurohypophysis (posterior lobe).

The anterior pituitary hormones are divided into two groups: growth hormone and prolactin and tropic hormones (thyrotropin, corticotropin, gonadotropin).

The first group includes somatotropin and prolactin.

Growth hormone (somatotropin) is involved in the regulation of growth, enhancing the formation of protein. Its influence on the growth of the epiphyseal cartilages of the extremities is most pronounced, the growth of bones goes in length. Violation of the somatotropic function of the pituitary gland leads to various changes in the growth and development of the human body: if there is hyperfunction in childhood, then gigantism develops; with hypofunction - dwarfism. With hyperfunction in an adult, but the size of those parts of the body that are still able to grow (acromegaly) increase.

Prolactin promotes the formation of milk in the alveoli, but after prior exposure to female sex hormones (progesterone and estrogen). After childbirth, the synthesis of prolactin increases and lactation occurs. Prolactin has a luteotropic effect, contributes to the long-term functioning of the corpus luteum and the production of progesterone by it.

The second group of hormones include: 1) thyroid-stimulating hormone (thyrotropin). Selectively acts on the thyroid gland, increases its function. With reduced production of thyrotropin, atrophy of the thyroid gland occurs, with hyperproduction - growth;

2) adrenocorticotropic hormone (corticotropin). Stimulates the production of glucocorticoids by the adrenal glands. Corticotropin causes breakdown and inhibits protein synthesis, is a growth hormone antagonist. It inhibits the development of the basic substance of connective tissue, reduces the number of mast cells, inhibits the enzyme hyaluronidase, reducing capillary permeability. This determines its anti-inflammatory effect. The secretion of corticotropin is subject to diurnal fluctuations: in the evening, its content is higher than in the morning;

3) gonadotropic hormones (gonadotropins - follitropin and lutropin). Present in both women and men;

a) follitropin (follicle-stimulating hormone), which stimulates the growth and development of the follicle in the ovary. It slightly affects the production of estrogen in women, in men, under its influence, spermatozoa are formed;

b) luteinizing hormone (lutropin), which stimulates the growth and ovulation of the follicle with the formation of the corpus luteum. It stimulates the formation of female sex hormones - estrogens. Lutropin promotes the production of androgens in men.

30. Hormones of the middle and posterior lobes of the pituitary gland

In the middle lobe of the pituitary gland, the hormone melanotropin (Intermedin) is produced, which affects the pigment metabolism.

The posterior pituitary gland is closely related to the supraoptic and paraventricular nucleus of the hypothalamus. The nerve cells of these nuclei produce a neurosecrete, which is transported to the posterior pituitary gland. Hormones accumulate in pituicites, in these cells the hormones are converted into an active form. Oxytocin is formed in the nerve cells of the paraventricular nucleus, and vasopressin is formed in the neurons of the supraoptic nucleus.

Vasopressin performs two functions:

1) enhances the contraction of vascular smooth muscles;

2) inhibits the formation of urine in the kidneys. The antidiuretic effect is provided by the ability of vasopressin to enhance the reabsorption of water from the tubules of the kidneys into the blood. A decrease in the formation of vasopressin is the cause of diabetes insipidus (diabetes insipidus).

Oxytocin selectively acts on the smooth muscles of the uterus, enhances its contraction. The contraction of the uterus increases dramatically if it was under the influence of estrogens. During pregnancy, oxytocin does not affect the contractility of the uterus, since the corpus luteum hormone progesterone makes it insensitive to all stimuli. Oxytocin stimulates the secretion of milk, it is the excretory function that is enhanced, and not its secretion. Special cells of the mammary gland selectively respond to oxytocin. The act of sucking reflexively promotes the release of oxytocin from the neurohypophysis.

Hypothalamic regulation of pituitary hormone production

Neurons of the hypothalamus produce neurosecretion. Neurosecretion products that contribute to the formation of hormones of the anterior pituitary gland are called liberins, and those that inhibit their formation are called statins. The entry of these substances into the anterior pituitary occurs through the blood vessels.

The regulation of the formation of hormones of the anterior pituitary gland is carried out according to the feedback principle. There are two-way relationships between the tropic function of the anterior pituitary gland and peripheral glands: tropic hormones activate peripheral endocrine glands, the latter, depending on their functional state, also affect the production of tropic hormones. Bilateral relationships exist between the anterior pituitary gland and the sex glands, the thyroid gland and the adrenal cortex. These relationships are called "plus-minus" interactions. Tropic hormones stimulate the function of the peripheral glands, and hormones of the peripheral glands inhibit the production and release of hormones from the anterior pituitary gland. There is an inverse relationship between the hypothalamus and the tropic hormones of the anterior pituitary gland. An increase in the concentration of pituitary hormone in the blood leads to inhibition of neurosecretion in the hypothalamus.

31. Hormones of the epiphysis, thymus, parathyroid glands

The epiphysis is located above the superior tubercles of the quadrigemina. The meaning of the epiphysis is extremely controversial. Two compounds have been isolated from its tissue:

1) melatonin (takes part in the regulation of pigment metabolism, inhibits the development of sexual functions in young people and the action of gonadotropic hormones in adults). This is due to the direct action of melatonin on the hypothalamus, where there is a blockade of the release of luliberin, and on the anterior pituitary gland, where it reduces the effect of luliberin on the release of lutropin;

2) glomerulotropin (stimulates the secretion of aldosterone by the adrenal cortex).

The thymus (thymus gland) is a paired lobular organ located in the upper part of the anterior mediastinum. The thymus produces several hormones: thymosin, homeostatic thymic hormone, thymopoietin I, II, thymic humoral factor. They play an important role in the development of immunological protective reactions of the body, stimulating the formation of antibodies. The thymus controls the development and distribution of lymphocytes.

The thymus reaches its maximum development in childhood. After puberty, it begins to atrophy (the gland stimulates the growth of the body and inhibits the development of the reproductive system). There is an assumption that the thymus affects the exchange of Ca ions and nucleic acids.

With an increase in the thymus gland in children, thymic-lymphatic status occurs. In this condition, in addition to an increase in the thymus, proliferation of lymphatic tissue occurs.

The parathyroid glands are a paired organ located on the surface of the thyroid gland. The parathyroid hormone is parathormon (parathyrin). Parathyroid hormone is found in the cells of the gland in the form of a prohormone, the transformation of prohormone into parathyroid hormone occurs in the Golgi complex.

From the parathyroid glands, the hormone directly enters the bloodstream.

Parathyroid hormone regulates Ca metabolism in the body and maintains its constant level in the blood. The bone tissue of the skeleton is the main depot of Ca in the body. There is a definite relationship between the level of Ca in the blood and its content in the bone tissue. Parathyroid hormone enhances bone resorption, which leads to an increase in the release of Ca ions, regulates the processes of deposition and release of Ca salts in the bones. Parathyroid hormone simultaneously affects the exchange of phosphorus: it reduces the reabsorption of phosphates in the distal tubules of the kidneys, which leads to a decrease in their concentration in the blood.

Removal of the parathyroid glands leads to lethargy, vomiting, loss of appetite, to scattered contractions of individual muscle groups, which can turn into a prolonged tetanic contraction.

The regulation of the activity of the parathyroid glands is determined by the level of Ca in the blood. If the concentration of Ca increases in the blood, this leads to a decrease in the functional activity of the parathyroid glands.

32. Thyroid hormones. thyrocalcitonin. Thyroid dysfunction

The thyroid gland is located on both sides of the trachea below the thyroid cartilage, has a lobular structure. The structural unit is a follicle filled with a colloid, where there is an iodine-containing protein - thyroglobulin.

Thyroid hormones are divided into two groups:

1) iodized - thyroxine, triiodothyronine;

2) thyrocalcitonin (calcitonin). Iodized hormones are produced in the follicles

glandular tissue.

The main active thyroid hormone is thyroxine, the ratio of thyroxine and triiodothyronine is 4: 1. Both hormones are in the blood in an inactive state, they are associated with proteins of the globulin fraction and blood plasma albumin.

The role of iodinated hormones:

1) influence on the functions of the central nervous system. Hypofunction leads to a sharp decrease in motor excitability;

2) influence on higher nervous activity. They are included in the process of developing conditioned reflexes;

3) impact on growth and development;

4) influence on metabolism;

5) influence on the vegetative system. The number of heartbeats, respiratory movements increases, sweating increases;

6) influence on the blood coagulation system. Reduce the ability of blood to coagulate, increase its fibrinolytic activity.

Thyrocalcitocin is produced by the parafollicular cells of the thyroid gland, which are located outside the glandular follicles. It takes part in the regulation of calcium metabolism, under its influence the level of Ca decreases. Thyrocalcitocin lowers the content of phosphates in the peripheral blood.

Thyrocalcitocin inhibits the release of Ca ions from bone tissue and increases its deposition in it.

The secretion of thyrocalcitonin is promoted by some biologically active substances: gastrin, glucagon, cholecystokinin.

Insufficiency of hormone production (hypothyroidism), which appears in childhood, leads to the development of cretinism (growth, sexual development, mental development are delayed, there is a violation of body proportions).

Lack of hormone production leads to the development of myxedema, which is characterized by a sharp disorder in the processes of excitation and inhibition in the central nervous system, mental retardation, decreased intelligence, lethargy, and drowsiness.

With an increase in the activity of the thyroid gland (hyperthyroidism), the disease occurs thyrotoxicosis. Characteristic signs: an increase in the size of the thyroid gland, the number of heartbeats, an increase in metabolism. Increased excitability and irritability are observed.

33. Pancreatic hormones

Pancreatic dysfunction

The pancreas is a mixed function gland.

The morphological unit of the gland is the islets of Langerhans. Islet beta cells produce insulin, alpha cells produce glucagon, and delta cells produce somatostatin.

Insulin regulates carbohydrate metabolism, reduces the concentration of sugar in the blood, promotes the conversion of glucose into glycogen in the liver and muscles. It increases the permeability of cell membranes for glucose: once inside the cell, glucose is absorbed. Insulin delays the breakdown of proteins and their conversion into glucose regulates fat metabolism through the formation of higher fatty acids from the products of carbohydrate metabolism. Insulin regulation is based on the normal content of glucose in the blood: hyperglycemia leads to an increase in the flow of insulin into the blood, and vice versa.

Glucagon increases the amount of glucose, which also leads to an increase in insulin production. The adrenal hormones work in a similar way.

The autonomic nervous system regulates insulin production through the vagus and sympathetic nerves. The vagus nerve stimulates insulin release, while the sympathetic nerve inhibits it.

Glucagon is involved in the regulation of carbohydrate metabolism; by its action on carbohydrate metabolism, it is an insulin antagonist.

The formation of glucagon in alpha cells is influenced by the level of glucose in the blood.

Growth hormone somatotropin increases the activity of alpha cells. In contrast, the delta cell hormone somatostatin inhibits the formation and secretion of glucagon, as it blocks the entry into alpha cells of Ca ions, which are necessary for the formation and secretion of glucagon.

Physiological significance of lipocaine. It promotes fat utilization by stimulating lipid formation and fatty acid oxidation in the liver.

The functions of vagotonin are an increase in the tone of the vagus nerves, an increase in their activity.

Functions of centropnein - excitation of the respiratory center, promoting relaxation of the smooth muscles of the bronchi.

Violation of the function of the pancreas.

A decrease in insulin secretion leads to the development of diabetes mellitus, the main symptoms of which are hyperglycemia, glucosuria, polyuria (up to 10 liters per day), polyphagia (increased appetite), polydyspepsia (increased thirst).

An increase in blood sugar in diabetic patients is the result of a loss in the ability of the liver to synthesize glycogen from glucose, and cells to utilize glucose. In the muscles, the process of formation and deposition of glycogen also slows down.

In diabetic patients, all types of metabolism are disturbed.

34. Adrenal hormones

Glucocorticoids

The adrenal glands are paired glands located above the upper poles of the kidneys. There are two types of hormones: cortical hormones and medulla hormones.

The hormones of the cortical layer last into three groups:

1) glucocorticoids (hydrocortisone, cortisone, corticosterone);

2) mineralocorticoids (aldesterone, deoxycorticosterone);

3) sex hormones (androgens, estrogens, progesterone).

Glucocorticoids are synthesized in the zona fasciculata of the adrenal cortex.

Physiological significance of glucocorticoids.

Glucocorticoids affect the metabolism of carbohydrates, proteins and fats, enhance the formation of glucose from proteins, increase the deposition of glycogen in the liver, and are insulin antagonists in their action.

Glucocorticoids have a catabolic effect on protein metabolism.

Hormones have an anti-inflammatory effect, which is due to a decrease in the permeability of the vessel walls with a low activity of the hyaluronidase enzyme. The decrease in inflammation is due to the inhibition of the release of arachidonic acid from phospholipids.

Glucocorticoids affect the production of protective antibodies: hydrocortisone inhibits the synthesis of antibodies, inhibits the reaction of the interaction of an antibody with an antigen.

Glucocorticoids have a pronounced effect on the hematopoietic organs:

1) increase the number of red blood cells by stimulating the red bone marrow;

2) lead to the reverse development of the thymus and lymphoid tissue, which is accompanied by a decrease in the number of lymphocytes.

Excretion from the body is carried out in two ways:

1) 75-90% of the hormones that enter the blood are removed with urine;

2) 10-25% is removed with feces and bile. Regulation of the formation of glucocorticoids.

An important role in the formation of glucocorticoids is played by corticotropin of the anterior pituitary gland.

This effect is carried out according to the principle of direct and feedback: corticotropin increases the production of glucocorticoids, and their excessive content in the blood leads to inhibition of corticotropin in the pituitary gland.

In the nuclei of the anterior hypothalamus, the neurosecrete corticoliberin is synthesized, which stimulates the formation of corticotropin in the anterior pituitary gland, and it, in turn, stimulates the formation of glucocorticoid.

Adrenaline - the hormone of the adrenal medulla - enhances the formation of glucocorticoids.

35. Adrenal hormones. Mineralocorticoids. sex hormones

Mineralocorticoids are formed in the glomerular zone of the adrenal cortex and take part in the regulation of mineral metabolism. These include al-dosterone and deoxycorticosterone. They increase the reabsorption of Na ions in the renal tubules and reduce the reabsorption of K ions, which leads to an increase in Na ions in the blood and tissue fluid and an increase in their osmotic pressure. This causes water retention in the body and an increase in blood pressure.

Mineralocorticoids contribute to the manifestation of inflammatory reactions by increasing the permeability of capillaries and serous membranes. Aldosterone has the ability to increase the tone of the smooth muscles of the vascular wall, which leads to an increase in blood pressure. With a lack of aldosterone, hypotension develops.

Regulation of mineralocorticoid formation

The secretion and formation of aldosterone is regulated by the renin-angiotensin system. Renin is formed in special cells of the juxtaglomerular apparatus of the afferent arterioles of the kidney and is released into the blood and lymph. It catalyzes the conversion of angiotensinogen to angiotensin I, which is converted under the action of a special enzyme into angiotensin II. Angiotensin II stimulates the formation of aldosterone. The synthesis of mineralocorticoids is controlled by the concentration of Na and K ions in the blood. A decrease in the formation of mineralocorticoids occurs with an insufficient content of K ions. The amount of tissue fluid and blood plasma affects the synthesis of mineralocorticoids. An increase in their volume leads to inhibition of aldosterone secretion, which is due to increased release of Na ions and water associated with it. The pineal hormone glomerulotropin enhances the synthesis of aldosterone.

Sex hormones (androgens, estrogens, progesterone) are produced in the reticular zone of the adrenal cortex. They are of great importance in the development of the genital organs in childhood, when the intrasecretory function of the sex glands is negligible. They have an anabolic effect on protein metabolism: they increase protein synthesis due to the increased inclusion of amino acids in its molecule.

With hypofunction of the adrenal cortex, a disease occurs - bronze disease, or Addison's disease. Signs of this disease are: bronze coloration of the skin, especially on the hands, neck, face, fatigue, loss of appetite, nausea and vomiting. The patient becomes sensitive to pain and cold, more susceptible to infection.

With hyperfunction of the adrenal cortex (the cause of which is most often a tumor), there is an increase in the formation of hormones, there is a predominance of the synthesis of sex hormones over others, so secondary sexual characteristics begin to change dramatically in patients.

In women, there is a manifestation of secondary male sexual characteristics, in men - female.

36. Hormones of the adrenal medulla and sex hormones

The adrenal medulla produces hormones related to catecholamines. The main hormone is adrenaline, the second most important is the precursor of adrenaline - norepinephrine.

Significance of adrenaline and norepinephrine

Adrenaline performs the function of a hormone, it enters the blood constantly, under various conditions of the body (blood loss, stress, muscle activity). Excitation of the sympathetic nervous system leads to an increase in the flow of adrenaline and norepinephrine into the blood. Adrenaline affects carbon metabolism, accelerates the breakdown of glycogen in the liver and muscles, relaxes bronchial muscles, inhibits gastrointestinal motility and increases the tone of its sphincters, increases the excitability and contractility of the heart muscle. It increases the tone of blood vessels, acts as a vasodilator on the vessels of the heart, lungs and brain. Adrenaline enhances the performance of skeletal muscles.

An increase in the activity of the adrenal system occurs under the influence of various stimuli that cause a change in the internal environment of the body. Adrenaline blocks these changes.

Norepinephrine performs the function of a mediator, it is part of sympathin, a mediator of the sympathetic nervous system, it takes part in the transmission of excitation in CNS neurons.

The secretory activity of the adrenal medulla is regulated by the hypothalamus.

The sex glands (testes in men, ovaries in women) are glands with a mixed function, the intrasecretory function is manifested in the formation and secretion of sex hormones that directly enter the bloodstream.

Male sex hormones - androgens are formed in the interstitial cells of the testes. There are two types of androgens - testosterone and androsterone.

Androgens stimulate the growth and development of the reproductive apparatus, male sexual characteristics and the appearance of sexual reflexes. They control the process of maturation of spermatozoa, contribute to the preservation of their motor activity, the manifestation of sexual instinct and sexual behavioral reactions, increase the formation of protein, especially in muscles.

The female sex hormones estrogens are produced in the ovarian follicles. The synthesis of estrogens is carried out by the follicle membrane, progesterone - by the corpus luteum of the ovary.

Estrogens stimulate the growth of the uterus, vagina, tubes, cause the growth of the endometrium, contribute to the development of secondary female sexual characteristics, the manifestation of sexual reflexes, and increase the contractility of the uterus.

Progesterone ensures the normal course of pregnancy.

The formation of sex hormones is under the influence of gonadotropic hormones of the pituitary gland and prolactin.

37. The concept of higher and lower nervous activity

Lower nervous activity is an integrative function of the spinal and brainstem, which is aimed at the regulation of vegetative-visceral reflexes.

Higher nervous activity is inherent only in the brain, which controls the individual behavioral reactions of the organism in the environment. It has a number of features.

1. The cerebral cortex and subcortical formations act as a morphological substrate.

2. Controls contact with the surrounding reality.

3. Instincts and conditioned reflexes underlie the mechanisms of emergence.

Instincts are innate, unconditioned reflexes and are a combination of motor acts and complex forms of behavior (food, sexual, self-preservation). They have features of manifestation and functioning associated with physiological properties:

1) the morphological substrate is the limbic system, basal ganglia, hypothalamus;

2) are of a chain nature;

3) the humoral factor is of great importance for manifestation;

4) have ready-made reflex arcs;

5) form the basis for conditioned reflexes;

6) are inherited and have specific character;

7) differ in constancy and change little during life;

8) do not require additional conditions for manifestation, they arise on the action of an adequate stimulus. Conditioned reflexes are developed throughout life, since they do not have ready-made reflex arcs. They are individual in nature and, depending on the conditions of existence, can constantly change. Their features:

1) the morphological substrate is the cerebral cortex, when it is removed, the old reflexes disappear;

2) on their basis, the interaction of the organism with the external environment is formed.

So, conditioned reflexes are a set of behavioral reactions acquired during life. Their classification:

1) according to the nature of the conditioned stimulus, natural and artificial reflexes are distinguished. Natural reflexes are developed for the natural qualities of the stimulus (for example, the type of food), and artificial - for any;

2) according to the receptor sign - exteroceptive, interoceptive and proprioceptive;

3) depending on the structure of the conditioned stimulus - simple and complex;

4) along the efferent path - somatic (motor) and vegetative;

5) according to biological significance - vital (food, defensive, locomotor), zoosocial, indicative.

38. Formation of conditioned reflexes and the mechanism of their inhibition

Certain conditions are necessary for the formation of conditioned reflexes.

1. The presence of two stimuli - indifferent and unconditioned. This is due to the fact that an adequate stimulus will cause an unconditioned reflex, and already on its basis a conditioned one will be developed.

2. A certain combination in time of two stimuli. First, the indifferent must turn on, and then the unconditional, and the intermediate time must be constant.

3. A certain combination of the strength of two stimuli. Indifferent - threshold, and unconditional - superthreshold.

4. The usefulness of the central nervous system.

5. Absence of extraneous irritants.

6. Repeated repetition of the action of stimuli for the emergence of a dominant focus of excitation.

This process is based on two mechanisms: unconditional (external) and conditional (internal) inhibition.

Unconditional inhibition occurs instantly due to the cessation of conditioned reflex activity. Allocate external and transcendental braking.

To activate external inhibition, the action of a new strong stimulus is necessary, capable of creating a dominant focus of excitation in the cerebral cortex. As a result, the work of all nerve centers is inhibited, and the temporary nervous connection ceases to function.

Limiting inhibition plays a protective role and protects neurons from overexcitation.

For the occurrence of conditional inhibition, the presence of special conditions (for example, the absence of signal reinforcement) is necessary. There are four types of braking:

1) fading (eliminates unnecessary reflexes due to the lack of their reinforcement);

2) trim (leads to the sorting of close stimuli);

3) delayed (occurs when the duration of the action between two signals increases);

4) conditioned brake (appears only under the action of an additional stimulus of moderate strength).

Inhibition frees the body from unnecessary reflex connections and further complicates the relationship of man with the environment.

A dynamic stereotype is a developed and fixed system of reflex connections. It consists of an external and an internal component. The external is based on a certain sequence of conditional and unconditional signals. The basis for the internal is the emergence of foci of excitation in the cerebral cortex adequate to this effect.

39. The concept of the types of the nervous system. Signal system

The type of the nervous system is a set of processes occurring in the cerebral cortex. It depends on the genetic predisposition and may vary slightly over the course of an individual's life. The main properties of the nervous process are balance, mobility, strength.

Balance is characterized by the same intensity of the processes of excitation and inhibition in the central nervous system.

Mobility is determined by the rate at which one process is replaced by another. Strength depends on the ability to respond adequately to both strong and super-strong stimuli.

According to the intensity of these processes, IP Pavlov identified four types of the nervous system, two of which he called extreme due to weak nervous processes, and two - central.

People with type I nervous system (melancholic) are cowardly, tearful, attach great importance to any trifle, pay increased attention to difficulties. This is the inhibitory type of the nervous system. Type II individuals are characterized by aggressive and emotional behavior, rapid mood swings. They are dominated by strong and unbalanced processes, according to Hippocrates - choleric. Sanguine people - type III - are confident leaders, they are energetic and enterprising.

Their nervous processes are strong, mobile and balanced. Phlegmatic - type IV - quite calm and self-confident, with strong balanced and mobile nervous processes.

The signal system is a set of conditioned reflex connections of the organism with the environment, which subsequently serves as the basis for the formation of higher nervous activity. According to the time of formation, the first and second signal systems are distinguished. The first signaling system is a complex of reflexes to a specific stimulus, for example, to light, sound, etc. It is carried out due to specific receptors that perceive reality in specific images. In this signaling system, the sense organs play an important role, transmitting excitation to the cerebral cortex, in addition to the brain section of the speech-motor analyzer. The second signal system is formed on the basis of the first and is a conditioned reflex activity in response to a verbal stimulus. It functions due to speech-motor, auditory and visual analyzers.

The signaling system also affects the type of nervous system. Types of the nervous system:

1) medium type (there is the same severity);

2) artistic (the first signal system prevails);

3) thinking (the second signal system is developed);

4) artistic and mental (both signal systems are simultaneously expressed).

40. Components of the circulatory system. Circles of blood circulation. Features of the heart

The circulatory system consists of four components: the heart, blood vessels, organs - blood depots, regulation mechanisms.

The circulatory system is a constituent component of the cardiovascular system, which, in addition to the circulatory system, includes the lymphatic system.

In the human body, blood circulates through two circles of blood circulation - large and small, which, together with the heart, form a closed system.

The pulmonary circulation begins in the right ventricle and continues into the pulmonary trunk, passes into the lungs, where gas exchange takes place, then the blood enters the left atrium through the pulmonary veins. The blood is enriched with oxygen. From the left atrium, arterial blood, saturated with oxygen, enters the left ventricle, from where a large circle begins. Blood containing oxygen is sent through the aorta through smaller vessels to tissues and organs where gas exchange takes place.

A feature is the fact that in a large circle arterial blood moves through the arteries, and venous blood - through the veins.

The heart is a four-chambered organ, consisting of two atria, two ventricles and two auricles. It is with the contraction of the atria that the work of the heart begins. Outside the heart is the pericardium - the pericardial sac.

The heart is divided by a vertical septum into right and left halves, which normally do not communicate with each other in an adult. The horizontal septum is formed by fibrous fibers and divides the heart into atria and ventricles, which are connected by an atrioventricular plate. There are two types of valves in the heart - cuspid and semilunar.

The valve is a duplication of the endocardium, in the layers of which there are connective tissue, muscle elements, blood vessels and nerve fibers.

The leaf valves are located between the atrium and the ventricle, with three valves in the left half and two in the right half. The semilunar valves are located at the point of exit from the ventricles of the blood vessels - the aorta and the pulmonary trunk.

The cycle of cardiac activity consists of systole and diastole. Systole is a contraction that lasts 0,1-0,16 s in the atrium and 0,3-0,36 s in the ventricle. Atrial systole is weaker than ventricular systole. Diastole - relaxation, in the atria takes 0,7-0,76 s, in the ventricles - 0,47-0,56 s. The duration of the cardiac cycle is 0,8-0,86 s and depends on the frequency of contractions. The time during which the atria and ventricles are at rest is called the total pause in the activity of the heart. It lasts approximately 0,4 s. During this time the heart rests

41. Properties and structure of the myocardium

The myocardium is represented by a striated muscle tissue, consisting of individual cells - cardiomyocytes, interconnected by nexus, and forming the muscle fiber of the myocardium.

According to the features of functioning, two types of muscles are distinguished: the working myocardium and atypical muscles.

The working myocardium is formed by muscle fibers with a well-developed striated striation. The working myocardium has a number of physiological properties:

1) excitability;

2) conductivity;

3) low lability;

4) contractility;

5) refractoriness.

Excitability is the ability of a striated muscle to respond to nerve impulses.

Due to the low speed of conduction of excitation, alternate contraction of the atria and ventricles is provided.

The refractory period is quite long and is related to the period of action. The heart can contract as a single muscle contraction.

Atypical muscle fibers have mild contraction properties and have a fairly high level of metabolic processes. This is due to the presence of mitochondria, which perform a function close to the function of the nervous tissue, i.e., it provides the generation and conduction of nerve impulses.

Atypical myocardium forms the conduction system of the heart. Physiological properties of atypical myocardium:

1) excitability is lower than that of skeletal muscles, but higher than that of contractile myocardial cells, therefore it is here that the generation of nerve impulses occurs;

2) conductivity is less than that of skeletal muscles, but higher than that of contractile myocardium;

3) the refractory period is quite long and is associated with the occurrence of an action potential and calcium ions;

4) low lability;

5) low ability to contractility;

6) automation.

Atypical muscles form nodes and bundles in the heart, which are combined into a conduction system. It includes:

1) sinoatrial node or Keyes-Fleck;

2) atrioventricular node;

3) bundle of His;

4) Purkinje fibers.

There are also additional structures:

1) Kent bundles;

2) Maygail's bundle.

These additional tracts provide the transmission of impulses when the atrioventricular node is turned off, that is, they cause unnecessary information in pathology and can cause an extraordinary contraction of the heart - an extrasystole.

42. Automatic heart

Automation is the ability of the heart to contract under the influence of impulses that arise in itself. It has been found that nerve impulses can be generated in atypical myocardial cells. In a healthy person, this occurs in the region of the sinoatrial node, since these cells differ from other structures in structure and properties. They are spindle-shaped, arranged in groups and surrounded by a common basal membrane. These cells are called first-order pacemakers, or pacemakers. They are metabolic processes at a high speed, so the metabolites do not have time to be carried out and accumulate in the intercellular fluid. Also characteristic properties are the low value of the membrane potential and high permeability for Na and Ca ions. A rather low activity of the sodium-potassium pump was noted, which is due to the difference in the concentration of Na and K.

Automation occurs in the diastolic phase and is manifested by the movement of Na ions into the cell. At the same time, the value of the membrane potential decreases and tends to a critical level of depolarization - a slow spontaneous diastolic depolarization occurs, accompanied by a decrease in the membrane charge. In the phase of rapid depolarization, the opening of channels for Na and Ca ions occurs, and they begin their movement into the cell. As a result, the membrane charge decreases to zero and reverses, reaching +20-30 mV. The movement of Na occurs until electrochemical equilibrium is reached for Na ions, then the plateau phase begins. In the plateau phase, Ca ions continue to enter the cell. At this time, the heart tissue is non-excitable. Upon reaching the electrochemical equilibrium for Ca ions, the plateau phase ends and a period of repolarization begins - the return of the membrane charge to its original level.

The action potential of the sinoatrial node has a smaller amplitude and is ± 70-90 mV, and the usual potential is equal to ± 120-130 mV.

Normally, potentials arise in the sinoatrial node due to the presence of cells - pacemakers of the first order. But other parts of the heart, under certain conditions, are also able to generate a nerve impulse. This occurs when the sinoatrial node is turned off and when additional stimulation is turned on.

When the sinoatrial node is turned off, generation of nerve impulses is observed at a frequency of 50-60 times per minute in the atrioventricular node - the pacemaker of the second order. In case of violation in the atrioventricular node with additional irritation, excitation occurs in the cells of the His bundle with a frequency of 30-40 times per minute - a pacemaker of the third order.

The automaticity gradient is a decrease in the ability to automaticity as you move away from the sinoatrial node, that is, from the place of direct generalization of impulses.

43. Coronary blood flow, its features

For the full-fledged work of the myocardium, a sufficient supply of oxygen is necessary, which is provided by the coronary arteries. They begin at the base of the aortic arch. The right coronary artery supplies most of the right ventricle, the interventricular septum, the posterior wall of the left ventricle, and the remaining departments are supplied by the left coronary artery. The coronary arteries are located in the groove between the atrium and the ventricle and form numerous branches. The arteries are accompanied by coronary veins that drain into the venous sinus.

Features of coronary blood flow:

1) high intensity;

2) the ability to extract oxygen from the blood;

3) the presence of a large number of anastomoses;

4) high tone of smooth muscle cells during contraction;

5) a significant amount of blood pressure.

Due to the presence of anastomoses, arteries and veins are connected to each other bypassing the capillaries.

Coronary blood flow is characterized by relatively high blood pressure.

During systole, up to 15% of blood enters the heart, and during diastole - up to 85%. This is due to the fact that during systole, contracting muscle fibers compress the coronary arteries. As a result, there is a portion ejection of blood from the heart, which is reflected in the magnitude of blood pressure.

Autoregulation can be carried out in two ways - metabolic and myogenic. The metabolic method of regulation is associated with a change in the lumen of the coronary vessels due to substances formed as a result of metabolism. Expansion of coronary vessels occurs under the influence of several factors:

1) lack of oxygen leads to an increase in the intensity of blood flow;

2) an excess of carbon dioxide causes an accelerated outflow of metabolites;

3) adenosyl promotes the expansion of the coronary arteries and increased blood flow.

A weak vasoconstrictor effect occurs with an excess of pyruvate and lactate.

The myogenic effect of Ostroumov-Beilis is that smooth muscle cells begin to contract to stretch when blood pressure rises and relax when it falls.

Nervous regulation of coronary blood flow is carried out mainly by the sympathetic division of the autonomic nervous system and is activated with an increase in the intensity of coronary blood flow.

Humoral regulation is similar to the regulation of all types of vessels.

44. Reflex influences on the activity of the heart

The so-called cardiac reflexes are responsible for the two-way communication of the heart with the central nervous system. Currently, there are three reflex influences - own, conjugated, non-specific.

Own cardiac reflexes occur when receptors in the heart and blood vessels are excited. They lie in the form of accumulations - reflexogenic or receptive fields of the cardiovascular system.

In the area of reflexogenic zones, there are mechano- and chemoreceptors. Mechanoreceptors will respond to changes in pressure in the vessels, to stretching, to changes in fluid volume. Chemoreceptors respond to changes in the chemical composition of the blood. Under normal conditions, these receptors are characterized by constant electrical activity. There are six types of intrinsic reflexes:

1) Bainbridge reflex;

2) influence from the area of carotid sinuses;

3) influence from the area of the aortic arch;

4) influence from the coronary vessels;

5) influence from pulmonary vessels;

6) influence from pericardial receptors. Reflex influences from the region of the carotid sinuses - ampoule-shaped extensions of the internal carotid artery at the site of bifurcation of the common carotid artery. With an increase in pressure, impulses from these receptors increase, impulses are transmitted along the fibers of the IV pair of cranial nerves, and activity increases! X pair of cranial nerves. As a result, irradiation of excitation occurs, and it is transmitted along the fibers of the vagus nerves to the heart, leading to a decrease in the strength and frequency of heart contractions.

With a decrease in pressure in the region of the carotid sinuses, impulses in the central nervous system decrease, the activity of the IV pair of cranial nerves decreases, and a decrease in the activity of the nuclei of the X pair of cranial nerves is observed. The predominant influence of the sympathetic nerves occurs, causing an increase in the strength and frequency of heart contractions.

The value of reflex influences from the region of the carotid sinuses is to ensure self-regulation of the activity of the heart.

With an increase in pressure, reflex influences from the aortic arch lead to an increase in impulses along the fibers of the vagus nerves, which leads to an increase in the activity of the nuclei and a decrease in the strength and frequency of heart contractions, and vice versa.

With an increase in pressure, reflex influences from the coronary vessels lead to inhibition of the heart.

When the pericardium is stretched or irritated by chemicals, inhibition of cardiac activity is observed.

Thus, their own cardiac reflexes self-regulate the amount of blood pressure and the work of the heart.

45. Nervous regulation of the activity of the heart

Nervous regulation is characterized by a number of features.

1. The nervous system has a starting and corrective effect on the work of the heart.

2. The nervous system regulates the intensity of metabolic processes.

The heart is innervated by fibers of the central nervous system - extracardiac mechanisms and its own fibers - intracardiac. The intracardiac regulatory mechanisms are based on the metsympathetic nervous system, which contains all the necessary intracardiac formations for the emergence of a reflex arc and the implementation of local regulation. An important role is also played by the fibers of the parasympathetic and sympathetic divisions of the autonomic nervous system, which provide afferent and efferent innervation. Efferent parasympathetic fibers are represented by vagus nerves, bodies of preganglionic neurons I, located at the bottom of the rhomboid fossa of the medulla oblongata. Their processes end intramurally, and the bodies of the II postganglionic neurons are located in the heart system. The vagus nerves provide innervation to the formations of the conduction system: the right one - the sinoatrial node, the left one - the atrioventricular node.

The centers of the sympathetic nervous system lie in the lateral horns of the spinal cord at the level of the IV thoracic segments. It innervates the ventricular myocardium, the atrial myocardium, and the conduction system.

The centers of the nuclei that innervate the heart are in a state of constant moderate excitation, due to which nerve impulses arrive at the heart. The tone of the sympathetic and parasympathetic divisions is not the same. In an adult, the tone of the vagus nerves predominates.

It is supported by impulses coming from the central nervous system from receptors embedded in the vascular system. They lie in the form of nerve clusters of reflexogenic zones:

1) in the area of the carotid sinus;

2) in the region of the aortic arch;

3) in the area of coronary vessels.

The vagus and sympathetic nerves are antagonists and have five types of influence on the work of the heart:

1) chronotropic;

2) bathmotropic;

3) dromotropic;

4) inotropic;

5) tonotropic.

Parasympathetic nerves have a negative effect in all five directions, and sympathetic - on the contrary. The afferent nerves of the heart transmit impulses from the central nervous system to the endings of the vagus nerves - the primary sensory chemoreceptors that respond to changes in blood pressure. They are located in the myocardium of the atria and the left ventricle.

46. Humoral regulation of the activity of the heart and vascular tone

Factors of humoral regulation are divided into two groups:

1) substances of systemic action;

2) substances of local action.

Systemic substances include electrolytes and hormones. Electrolytes (Ca ions) have a pronounced effect on the work of the heart. With an excess of Ca, cardiac arrest can occur at the time of systole, since there is no complete relaxation. Na ions are able to have a moderate stimulating effect on the activity of the heart. K ions in high concentrations have an inhibitory effect on the work of the heart due to hyperpolarization.

The hormone adrenaline increases the strength and frequency of heart contractions.

Thyroxine (thyroid hormone) enhances the work of the heart.

Mineralocorticoids (aldosterone) stimulate Na reabsorption and K excretion from the body.

Glucagon raises blood glucose levels by breaking down glycogen, resulting in a positive inotropic effect.

Sex hormones in relation to the activity of the heart are synergists and enhance the work of the heart.

Substances of local action act where they are produced.

Vascular tone, depending on the origin, can be myogenic and nervous.

Myogenic tone occurs when certain vascular smooth muscle cells begin to spontaneously generate a nerve impulse. The resulting excitation spreads to other cells, and contraction occurs.

The nervous mechanism occurs in the smooth muscle cells of the vessels under the influence of impulses from the central nervous system.

Currently, there are three mechanisms of regulation of vascular tone - local, nervous, humoral.

Autoregulation provides a change in tone under the influence of local excitation. This mechanism is associated with relaxation and is manifested by the relaxation of smooth muscle cells. There is myogenic and metabolic autoregulation.

Nervous regulation is carried out under the influence of the autonomic nervous system, which acts as a vasoconstrictor and vasodilator.

Vasodilating nerves can be of various origins:

1) parasympathetic nature;

2) sympathetic nature;

3) axon reflex.

Humoral regulation is carried out by substances of local and systemic action.

Substances of local action include Ca, Na, Cu ions.

47. Functional system that maintains a constant level of blood pressure

A functional system that maintains the value of blood pressure at a constant level is a temporary set of organs and tissues that is formed when indicators deviate in order to return them to normal.

The functional system consists of four links:

1) useful adaptive result;

2) central link;

3) executive level;

4) feedback.

A useful adaptive result is the normal value of blood pressure, with a change in which the impulse from mechanoreceptors in the central nervous system increases, resulting in excitation.

The central link is represented by the vasomotor center. When its neurons are excited, the impulses converge and descend on one group of neurons - the acceptor of the result of the action.

The executive link includes internal organs:

1) heart;

2) vessels;

3) excretory organs;

4) organs of hematopoiesis and blood destruction;

5) depositing authorities;

6) respiratory system;

7) endocrine glands;

8) skeletal muscles that change motor activity.

When the desired result is achieved, the functional system disintegrates. At present, it is known that the central and executive mechanisms of a functional system are not switched on simultaneously, therefore, according to the time of switching on, they distinguish:

1) short-term mechanism;

2) intermediate mechanism;

3) long mechanism.

The mechanisms of short-term action turn on quickly, but the duration of their action is several minutes, a maximum of 1 hour. These include reflex changes in the work of the heart and the tone of blood vessels, that is, the nervous mechanism is the first to turn on.

The intermediate mechanism begins to act gradually over several hours. This mechanism includes:

1) change in transcapillary exchange;

2) decrease in filtration pressure;

3) stimulation of the reabsorption process;

4) relaxation of tense vascular muscles after an increase in their tone.

Long-acting mechanisms cause more significant changes in the functions of various organs and systems.

48. Essence and significance of breathing processes

Respiration is the most ancient process by which the regeneration of the gas composition of the internal environment of the body is carried out. As a result, organs and tissues are supplied with oxygen and give off carbon dioxide. The process of respiration consists of three main links - external respiration, transport of gases by blood, internal respiration.

External respiration. It is carried out using two processes - pulmonary respiration and respiration through the skin.

Pulmonary respiration consists in the exchange of gases between the alveolar air and the environment and between the alveolar air and capillaries. Oxygen enters from atmospheric air into the alveolar air, and carbon dioxide is released in the opposite direction.

The transport of gases by blood is carried out mainly in the form of complexes:

1) oxygen forms a compound with hemoglobin;

2) 15-20 ml of oxygen is transported in the form of physical dissolution;

3) carbon dioxide is transported in the form of Na and K bicarbonates;

4) carbon dioxide is transported along with the hemoglobin molecule.

Internal respiration consists of the exchange of gases between the capillaries of the systemic circulation and tissue and interstitial respiration. As a result, oxygen is utilized for oxidative processes.

The respiratory apparatus includes three components - the respiratory tract, lungs, chest, along with muscles.

The respiratory tract begins with the nasal passages, then continues into the larynx, trachea, bronchi. Due to the presence of a cartilaginous base and periodic changes in the tone of smooth muscle cells, the airway lumen is always open. The respiratory tract has a well-branched blood supply system, thanks to which the air is warmed and humidified.

The lungs are made up of alveoli with capillaries attached to them. There is an air-blood barrier between the lung tissue and the capillary.

The lungs perform many functions:

1) remove carbon dioxide and water in the form of vapors;

2) normalize the exchange of water in the body;

3) are blood depots of the second order;

4) take part in lipid metabolism in the process of surfactant formation;

5) are involved in the formation of various blood coagulation factors.

The chest, together with the muscles, forms a bag for the lungs. There is a group of inspiratory and expiratory muscles.

49. The mechanism of inhalation and exhalation. Breath pattern

In an adult, the respiratory rate is approximately 16-18 breaths per minute. It depends on the intensity of metabolic processes and the gas composition of the blood.

The respiratory cycle consists of three phases:

1) inhalation phases (lasts approximately 0,9-4,7 s);

2) expiratory phases (lasting 1,2-6,0 s);

3) respiratory pause (non-constant component). The type of breathing depends on the muscles, so they distinguish:

1) chest. It is carried out with the participation of the intercostal muscles and muscles of the 1-3rd respiratory gap, when inhaling, good ventilation of the upper section of the lungs is provided, typical for women and children under 10 years old;

2) abdominal. Inhalation occurs due to contractions of the diaphragm;

3) mixed. It is observed with the uniform work of all respiratory muscles.

In a calm state, breathing is an active process and consists of active inhalation and passive exhalation. Active inspiration begins under the influence of impulses coming from the respiratory center to the inspiratory muscles, causing their contraction. As a result of the pressure difference, air enters the lungs. Passive exhalation occurs after the cessation of impulses to the muscles, they relax, and the size of the chest decreases. With an increase in the respiratory rate, all phases are shortened. Negative intra-tripleural pressure is the pressure difference between the parietal and visceral pleura. It is always below atmospheric.

The elastic recoil of the lungs is the force with which the tissue tends to collapse. Pattern - a set of temporal and volumetric characteristics of the respiratory center, such as:

1) respiratory rate;

2) the duration of the respiratory cycle;

3) tidal volume;

4) minute volume;

5) maximum ventilation of the lungs, reserve volume of inhalation and exhalation;

6) vital capacity of the lungs.

The functioning of the external respiration apparatus can be judged by the volume of air entering the lungs during one respiratory cycle. The volume of air entering the lungs during maximum inhalation forms the total lung capacity. It is approximately 4,5-6 liters and consists of the vital capacity of the lungs and the residual volume.

The vital capacity of the lungs is the amount of air that a person can exhale after taking a deep breath.

Tidal volume is the amount of air that a person inhales and exhales at rest.

50. Physiological characteristics of the respiratory center, its humoral regulation

According to modern concepts, the respiratory center is a collection of neurons that provide a change in the processes of inhalation and exhalation and adaptation of the system to the needs of the body. There are several levels of regulation:

1) spinal;

2) bulbar;

3) suprapontal;

4) cortical.

The spinal level is represented by motor neurons of the anterior horns of the spinal cord, the axons of which innervate the respiratory muscles.

The neurons of the reticular formation of the medulla oblongata and the pons form the bulbar level.

The axons of these nerve cells can be directed to the motor neurons of the spinal cord (bulbar fibers) or be part of the dorsal and ventral nuclei (protobulbar fibers). The neurons of the medulla oblongata, which are part of the respiratory center, have two features:

1) have a reciprocal relationship;

2) can spontaneously generate nerve impulses.

The pneumotoxic center is formed by the nerve cells of the bridge. They are able to regulate the activity of underlying neurons and lead to a change in the processes of inhalation and exhalation. The suprapontal level is represented by the structures of the cerebellum and midbrain, which provide the regulation of motor activity and autonomic function.

The cortical component consists of neurons of the cerebral cortex, which affect the frequency and depth of breathing. Basically, they have a positive effect, especially on the motor and orbital zones.

The excitatory effect on the neurons of the respiratory center is exerted by:

1) decrease in oxygen concentration (hypoxemia);

2) increase in carbon dioxide content (hypercapnia);

3) an increase in the level of hydrogen protons (acidosis). Braking effect occurs as a result of:

1) increase in oxygen concentration (hyperoxemia);

2) lowering the content of carbon dioxide (hypocap-tion);

3) decrease in the level of hydrogen protons (alkalosis). Currently, scientists have identified five ways

influence of blood gas composition on the activity of the respiratory center:

1) local;

2) humoral;

3) through peripheral chemoreceptors;

4) through central chemoreceptors;

5) through chemosensitive neurons of the cerebral cortex.

51. Nervous regulation of the activity of neurons of the respiratory center

Nervous regulation is carried out mainly by reflex pathways. There are two groups of influences - episodic and permanent.

There are three types of permanent:

1) from peripheral chemoreceptors of the cardiovascular system (Heimans reflex);

2) from the proprioreceptors of the respiratory muscles;

3) from nerve endings of lung tissue stretching. During breathing, the muscles contract and relax. During inhalation, the lungs expand, and impulses from receptors along the fibers of the vagus nerves enter the respiratory center. Here, inhibition of inspiratory neurons occurs, which leads to the cessation of active inhalation and the onset of passive exhalation. The significance of this process is to ensure the beginning of exhalation.

When the vagus nerves are overloaded, the change of inhalation and exhalation is preserved.

The expiratory-relief reflex can only be detected during the experiment. If you stretch the lung tissue at the time of exhalation, then the onset of the next breath is delayed.

The paradoxical Head effect can be realized in the course of the experiment. With maximum stretching of the lungs at the time of inspiration, an additional breath or sigh is observed.

Episodic reflex influences include:

1) impulses from irritary receptors of the lungs;

2) influence from juxtaalveolar receptors;

3) influence from the mucous membrane of the respiratory tract;

4) influences from skin receptors.

Irritary receptors are located in the endothelial and subendothelial layers of the respiratory tract. They simultaneously perform the functions of mechanoreceptors and chemoreceptors. Mechanoreceptors have a high threshold of irritation and are excited with a significant collapse of the lungs. With a decrease in the volume of lung tissue, receptors send impulses to the neurons of the respiratory center, which leads to an additional breath.

Chemoreceptors respond to the appearance of dust particles in the mucus. When irritary receptors are activated, there is a feeling of sore throat and cough.

Juxtaalveolar receptors are located in the interstitium. They react to the appearance of chemicals - serotonin, histamine, nicotine, as well as to changes in fluid. This leads to a special type of shortness of breath with edema (pneumonia).

With strong irritation of the mucous membrane of the respiratory tract, breathing stops, and with moderate irritation, protective reflexes appear. For example, when the receptors of the nasal cavity are irritated, sneezing occurs, when the nerve endings of the lower respiratory tract are activated, coughing occurs.

When noceceptors are activated, breathing stops first, and then a gradual increase occurs.

52. Homeostasis and orguinochemical properties of blood

Homeostasis is a set of body fluids that bathe all organs and tissues and take part in metabolic processes, and includes blood plasma, lymph, interstitial, synovial and cerebrospinal fluids. Blood is called a universal fluid, since in order to maintain the normal functioning of the body, it must contain all the necessary substances, that is, the internal environment has constancy - homeostasis. But this constancy is relative, since all the time there is a consumption of substances and the release of metabolites - homeostasis.

Homeostasis is characterized by certain average statistical indicators, which can fluctuate within small limits and have seasonal, gender and age differences.

The physiological norm is the optimal level of vital activity, at which the body adapts to the conditions of existence by changing the intensity of metabolic processes.

The blood system has a number of features:

1) dynamism, i.e. the composition of the peripheral component can constantly change;

2) the lack of independent significance, since it performs all its functions in constant motion, that is, it functions together with the circulatory system.

Its components are formed in various organs. Blood performs many functions in the body:

1) transport;

2) respiratory;

3) nutritional;

4) excretory;

5) temperature control;

6) protective.

Blood also regulates the supply of nutrients to tissues and organs and maintains homeostasis.

Blood is a suspension, as it consists of shaped elements suspended in plasma - leukocytes, platelets and erythrocytes. The ratio of plasma and formed elements depends on where the blood is located. Plasma predominates in the circulating blood - 50-60%, the content of formed elements - 40-45%. In deposited blood, on the contrary, plasma - 40-45%, and formed elements - 50-60%. To determine the percentage of plasma and formed elements, the hematocrit index is calculated.

Physico-chemical properties of blood are determined by its composition:

1) suspension;

2) colloidal;

3) rheological;

4) electrolyte.

53. Blood plasma, its composition

Plasma is the liquid part of the blood and is a water-salt solution of proteins. Consists of 90-95% water and 8-10% solids. The composition of the dry residue includes inorganic and organic substances. Organic proteins include proteins, nitrogen-containing substances of non-protein nature, nitrogen-free organic components, and enzymes.

Proteins make up 7-8% of the dry residue (which is 67-75 g / l) and perform a number of functions. They differ in structure, molecular weight, content of various substances.

With an increase in the concentration of proteins, hyperproteinemia occurs, with a decrease - hypoproteinemia, with the appearance of pathological proteins - paraproteinemia, with a change in their ratio - dysproteinemia. Normally, albumins and globulins are present in plasma. Their ratio is determined by the protein coefficient, which is 1,5-2,0.

Albumins are finely dispersed proteins, the molecular weight of which is 70-000 D. They contain about 80-000% in plasma, which is 50-60 g / l.

Globulins are coarse molecules with a molecular weight of more than 100 D.

Due to this structure, globulins perform various functions:

1) protective;

2) transport;

3) pathological.

Plasma also contains amino acids, urea, uric acid, creatinine;

Their content is low, so they are referred to as residual blood nitrogen. The level of residual nitrogen is maintained due to the presence of proteins in food, the excretory function of the kidneys and the intensity of protein metabolism.

Organic substances in plasma are presented in the form of metabolic products of carbohydrates and lipids. Components of carbohydrate metabolism:

1) glucose, the content of which is normally 4,44-6,66 mmol / l in arterial blood and 3,33-5,55 mmol / l in venous blood and depends on the amount of carbohydrates in food, the state of the endocrine system;

2) lactic acid, the content of which rises sharply in critical conditions. Normally, its content is 1-1,1 mmol / l;

3) pyruvic acid (formed during the utilization of carbohydrates, normally contains approximately 80-85 mmol / l).

The product of lipid metabolism is cholesterol, which is involved in the synthesis of hormones, bile acids, the construction of the cell membrane, and performs an energy function.

54. Physiological structure of erythrocytes

Erythrocytes are red blood cells containing the respiratory pigment hemoglobin.

Formed in the red bone marrow, and destroyed in the spleen.

Depending on the size, they are divided into normocytes, microcytes and macrocytes.

The erythrocyte carries respiratory gases - oxygen and carbon dioxide.

The most important functions of the erythrocyte are:

1) respiratory;

2) nutritious;

3) enzymatic;

4) protective;

5) buffer.

Since red blood cells contain antigens, they are used in immunological reactions to detect antibodies in the blood.

Erythrocytes are the most numerous formed elements of blood. So, men normally contain 4,5-5,5 h 1012 / l, and women - 3,7-4,7 h 1012 / l.

Aging erythrocytes, due to a decrease in the ability to deform, get stuck in the millipore filters of the spleen, where they are absorbed by phagocytes. About 10% of cells are destroyed in the vascular bed.

Hemoglobin is one of the most important respiratory proteins involved in the transfer of oxygen from the lungs to the tissues. It is the main component of red blood cells, each of which contains approximately 280 million hemoglobin molecules.

Hemoglobin is a complex protein that belongs to the class of chromoproteins and consists of two components:

1) iron-containing heme - 4%;

2) globin protein - 96%.

There are four forms of hemoglobin:

1) oxyhemoglobin;

2) methemoglobin;

3) carboxyhemoglobin;

4) myoglobin.

Oxyhemoglobin contains ferrous iron and is able to bind oxygen. It carries gas to tissues and organs. Carboxyhemoglobin forms a compound with carbon monoxide. It has a high affinity for carbon monoxide, so the complex decomposes slowly. Myoglobin is similar in structure to hemoglobin and is found in muscles, especially in the heart. It binds oxygen, forming a depot, which is used by the body when the oxygen capacity of the blood decreases. Due to myoglobin, oxygen is provided to working muscles.

Hemoglobin performs respiratory and buffer functions. The oxygen capacity of blood is the maximum amount of oxygen that can be in 100 ml of blood.

55. The structure of leukocytes and platelets

Leukocytes are nucleated blood cells, the size of which is from 4 to 20 microns. Their life expectancy varies greatly and ranges from 4-5 to 20 days for granulocytes and up to 100 days for lymphocytes. The number of leukocytes is normal in men and women is the same and is 4-9 h 109 / l.

Leukocytes are divided into two groups: granulocytes (granular) and agranulocytes.

Among granulocytes in peripheral blood are found:

1) neutrophils - 46-76%;

2) eosinophils - 1-5%;

3) basophils - 0-1%.

In the group of nongranular cells, there are:

1) monocytes - 2-10%;

2) lymphocytes - 18-40%.

The percentage of leukocytes in the peripheral blood is called the leukocyte formula, the shifts of which in different directions indicate pathological processes occurring in the body. There is a shift to the right - a decrease in the function of the red bone marrow, accompanied by an increase in the number of old forms of neutrophilic leukocytes.

The shift to the left is a consequence of the strengthening of the functions of the red bone marrow, the number of young forms of leukocytes in the blood increases. Normally, the ratio between young and old forms of leukocytes is 0,065 and is called the regeneration index. Due to the presence of a number of physiological features, leukocytes are able to perform many functions. The most important of the properties are amoeboid mobility, migration phagocytosis.

Leukocytes perform protective, destructive, regenerative, enzymatic functions in the body.

Immunity is the body's ability to defend itself against genetically foreign substances and bodies.

Platelets are non-nuclear blood cells, 1,5-3,5 microns in diameter. They have a flattened shape, and their number in men and women is the same and is 180-320 h 109 / l.

The platelet contains two zones: the granule (the center where glycogen, blood coagulation factors, etc. are located) and the hyalomere (the peripheral part, consisting of the endoplasmic reticulum and Ca ions).

Platelets are characterized by the following properties:

1) amoeboid mobility;

2) fast destructibility;

3) the ability to phagocytosis;

4) the ability to adhere;

5) the ability to aggregate.

Platelets perform trophic and dynamic functions and regulate vascular tone and take part in blood coagulation processes.

56. Functions, significance of the urinary system

The excretion process is important for ensuring and maintaining the constancy of the internal environment of the body. The kidneys take an active part in this process, removing excess water, inorganic and organic substances, metabolic end products and foreign substances. The kidneys are a paired organ, one healthy kidney successfully maintains the stability of the internal environment of the body.

The kidneys perform a number of functions in the body.

1. They regulate the volume of blood and extracellular fluid (carry out voloreregulation), with an increase in blood volume, volomoreceptors of the left atrium are activated: secretion of antidiuretic hormone (ADH) is inhibited, urination increases, excretion of water and Na ions increases, which leads to the restoration of blood volume and extracellular fluid.

2. Osmoregulation is carried out - regulation of the concentration of osmotically active substances. With an excess of water in the body, the concentration of osmotically active substances in the blood decreases, which reduces the activity of the osmoreceptors of the supraoptic nucleus of the hypothalamus and leads to a decrease in the secretion of ADH and an increase in the release of water.

3. Regulation of ion exchange is carried out by reabsorption of ions in the renal tubules with the help of hormones.

4. Stabilize the acid-base balance. Normal blood pH is 7,36 and is maintained by a constant concentration of H ions.

5. Perform a metabolic function: participate in the metabolism of proteins, fats, carbohydrates. Reabsorption of amino acids provides material for protein synthesis. Fatty acids in the kidney cell are included in the composition of phospholipids and triglycerides.

6. Carry out an excretory function - the release of end products of nitrogen metabolism, foreign substances, excess organic substances that come with food or formed in the process of metabolism. The products of protein metabolism (urea, uric acid, creatinine, etc.) are filtered in the glomeruli, then reabsorbed in the renal tubules. All formed creatinine is excreted in the urine, uric acid undergoes significant reabsorption, urea - partial.

7. Perform an endocrine function - regulate erythropoiesis, blood coagulation, blood pressure due to the production of biologically active substances. The kidneys secrete biologically active substances: renin cleaves an inactive peptide from angiotensinogen, converts it into angiotensin I, which, under the action of an enzyme, passes into the active vasoconstrictor angiotensin II. Plasminogen activator (urokinase) increases urinary Na excretion. Erythropoietin stimulates erythropoiesis in the bone marrow, bradykinin is a powerful vasodilator.

The kidney is a homeostatic organ that takes part in maintaining the main indicators of the internal environment of the body.

Author: Drangoy M.G.

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