Anatomy test on the topic "Respiratory system. Breathing"

The respiratory center not only ensures the rhythmic alternation of inhalation and exhalation, but is also capable of changing the depth and frequency of respiratory movements, thereby adapting pulmonary ventilation to the current needs of the body. Environmental factors, for example the composition and pressure of atmospheric air, ambient temperature, and changes in the state of the body, for example during muscle work, emotional arousal, etc., affecting the metabolic rate, and, consequently, oxygen consumption and carbon dioxide release, affect the functional state of the respiratory center. As a result, the volume of pulmonary ventilation changes.

Like all other processes of automatic regulation of physiological functions, the regulation of breathing is carried out in the body based on the feedback principle. This means that the activity of the respiratory center, which regulates the supply of oxygen to the body and the removal of carbon dioxide formed in it, is determined by the state of the process it regulates. The accumulation of carbon dioxide in the blood, as well as the lack of oxygen, are factors that cause excitation of the respiratory center.

The importance of blood gas composition in the regulation of breathing was shown by Frederick through an experiment with cross-circulation. To do this, two dogs under anesthesia had their carotid arteries and separately jugular veins cut and cross-connected (Figure 2). After this connection and clamping of other neck vessels, the head of the first dog was supplied with blood not from its own body, but from the body of the second dog, the head of the second dog is from the body of the first.

If the trachea of ​​one of these dogs is clamped and thus suffocating the body, then after a while it stops breathing (apnea), while the second dog experiences severe shortness of breath (dyspnea). This is explained by the fact that constriction of the trachea in the first dog causes an accumulation of CO 2 in the blood of its body (hypercapnia) and a decrease in oxygen content (hypoxemia). Blood from the first dog's body enters the second dog's head and stimulates its respiratory center. As a result, increased breathing occurs - hyperventilation - in the second dog, which leads to a decrease in CO 2 tension and an increase in O 2 tension in the blood vessels of the body of the second dog. The oxygen-rich, carbon-dioxide-poor blood from this dog's body goes first to the head and causes apnea.

Figure 2 - Scheme of Frederick's cross-circulation experiment

Frederick's experience shows that the activity of the respiratory center changes with changes in the tension of CO 2 and O 2 in the blood. Let's consider the effect on breathing of each of these gases separately.

The importance of carbon dioxide tension in the blood in the regulation of respiration. An increase in carbon dioxide tension in the blood causes excitation of the respiratory center, leading to an increase in ventilation of the lungs, and a decrease in carbon dioxide tension in the blood inhibits the activity of the respiratory center, which leads to a decrease in ventilation of the lungs. The role of carbon dioxide in the regulation of breathing was proven by Holden in experiments in which a person was in a confined space of a small volume. As the oxygen content of the inhaled air decreases and the carbon dioxide content increases, dyspnea begins to develop. If you absorb the released carbon dioxide with soda lime, the oxygen content in the inhaled air can decrease to 12%, and there is no noticeable increase in pulmonary ventilation. Thus, the increase in the volume of ventilation of the lungs in this experiment is due to an increase in the content of carbon dioxide in the inhaled air.

In another series of experiments, Holden determined the volume of ventilation of the lungs and the content of carbon dioxide in the alveolar air when breathing a gas mixture with different contents of carbon dioxide. The results obtained are shown in Table 1.

breathing muscle gas blood

Table 1 - Volume of lung ventilation and carbon dioxide content in alveolar air

The data presented in Table 1 show that simultaneously with an increase in the content of carbon dioxide in the inhaled air, its content in the alveolar air, and therefore in the arterial blood, increases. At the same time, there is an increase in ventilation of the lungs.

The experimental results provided convincing evidence that the state of the respiratory center depends on the carbon dioxide content in the alveolar air. It was revealed that an increase in CO 2 content in the alveoli by 0.2% causes an increase in lung ventilation by 100%.

A decrease in the carbon dioxide content in the alveolar air (and, consequently, a decrease in its tension in the blood) reduces the activity of the respiratory center. This occurs, for example, as a result of artificial hyperventilation, i.e., increased deep and frequent breathing, which leads to a decrease in the partial pressure of CO 2 in the alveolar air and the tension of CO 2 in the blood. As a result, breathing stops. Using this method, i.e., by performing preliminary hyperventilation, you can significantly increase the time of voluntary breath holding. This is what divers do when they need to spend 2...3 minutes under water (the usual duration of voluntary breath-holding is 40...60 seconds).

The direct stimulating effect of carbon dioxide on the respiratory center has been proven through various experiments. Injection of 0.01 ml of a solution containing carbon dioxide or its salt into a certain area of ​​the medulla oblongata causes increased respiratory movements. Euler exposed isolated cat medulla oblongata to carbon dioxide and observed that this caused an increase in the frequency of electrical discharges (action potentials), indicating excitation of the respiratory center.

The respiratory center is influenced increasing the concentration of hydrogen ions. Winterstein in 1911 expressed the view that the excitation of the respiratory center is caused not by carbonic acid itself, but by an increase in the concentration of hydrogen ions due to an increase in its content in the cells of the respiratory center. This opinion is based on the fact that increased respiratory movements are observed when not only carbonic acid, but also other acids, such as lactic acid, are introduced into the arteries supplying the brain. Hyperventilation, which occurs with an increase in the concentration of hydrogen ions in the blood and tissues, promotes the release of part of the carbon dioxide contained in the blood from the body and thereby leads to a decrease in the concentration of hydrogen ions. According to these experiments, the respiratory center is a regulator of the constancy of not only the carbon dioxide tension in the blood, but also the concentration of hydrogen ions.

The facts established by Winterstein were confirmed in experimental studies. At the same time, a number of physiologists insisted that carbonic acid is a specific irritant of the respiratory center and has a stronger stimulating effect on it than other acids. The reason for this turned out to be that carbon dioxide penetrates more easily than the H+ ion through the blood-brain barrier, which separates the blood from the cerebrospinal fluid, which is the immediate environment that bathes the nerve cells, and more easily passes through the membrane of the nerve cells themselves. When CO 2 enters the cell, H 2 CO 3 is formed, which dissociates with the release of H+ ions. The latter are the causative agents of the cells of the respiratory center.

Another reason for the stronger effect of H 2 CO 3 compared to other acids is, according to a number of researchers, that it specifically affects certain biochemical processes in the cell.

The stimulating effect of carbon dioxide on the respiratory center is the basis of one measure that has found application in clinical practice. When the function of the respiratory center is weakened and the resulting insufficient supply of oxygen to the body, the patient is forced to breathe through a mask with a mixture of oxygen and 6% carbon dioxide. This gas mixture is called carbogen.

Mechanism of action of increased CO voltage 2 and increased concentration of H+ ions in the blood during respiration. For a long time it was believed that an increase in carbon dioxide tension and an increase in the concentration of H+ ions in the blood and cerebrospinal fluid (CSF) directly affect the inspiratory neurons of the respiratory center. It has now been established that changes in CO 2 voltage and the concentration of H + ions affect respiration, exciting chemoreceptors located near the respiratory center that are sensitive to the above changes. These chemoreceptors are located in bodies with a diameter of about 2 mm, located symmetrically on both sides of the medulla oblongata on its ventrolateral surface near the exit site of the hypoglossal nerve.

The importance of chemoreceptors in the medulla oblongata can be seen from the following facts. When these chemoreceptors are exposed to carbon dioxide or solutions with an increased concentration of H+ ions, stimulation of respiration is observed. Cooling of one of the chemoreceptor bodies of the medulla oblongata entails, according to Leschke's experiments, the cessation of respiratory movements on the opposite side of the body. If the chemoreceptor bodies are destroyed or poisoned by novocaine, breathing stops.

Along with With chemoreceptors of the medulla oblongata in the regulation of breathing, an important role belongs to chemoreceptors located in the carotid and aortic bodies. This was proven by Heymans in methodologically complex experiments in which the vessels of two animals were connected so that the carotid sinus and carotid body or aortic arch and aortic body of one animal were supplied with the blood of another animal. It turned out that an increase in the concentration of H + ions in the blood and an increase in CO 2 voltage cause excitation of carotid and aortic chemoreceptors and a reflex increase in respiratory movements.

There is evidence that 35% of the effect is caused by inhalation of air With high carbon dioxide content are due to the effect on chemoreceptors of an increased concentration of H + ions in the blood, and 65% are the result of an increase in CO 2 voltage. The effect of CO 2 is explained by the rapid diffusion of carbon dioxide through the chemoreceptor membrane and a shift in the concentration of H + ions inside the cell.

Let's consider the effect of lack of oxygen on breathing. Excitation of the inspiratory neurons of the respiratory center occurs not only when the carbon dioxide tension in the blood increases, but also when the oxygen tension decreases.

Reduced oxygen tension in the blood causes a reflex increase in respiratory movements, acting on the chemoreceptors of the vascular reflexogenic zones. Direct evidence that a decrease in oxygen tension in the blood excites the chemoreceptors of the carotid body was obtained by Gaymans, Neal and other physiologists by recording bioelectric potentials in the sinocarotid nerve. Perfusion of the carotid sinus with blood with reduced oxygen tension results in increased action potentials in this nerve (Figure 3) and increased respiration. After the destruction of chemoreceptors, a decrease in oxygen tension in the blood does not cause changes in respiration.

Figure 3 - Electrical activity of the sinus nerve (according to Neil) A- when breathing atmospheric air; B- when breathing a gas mixture containing 10% oxygen and 90% nitrogen. 1 - recording of electrical activity of the nerve; 2 - recording of two pulse fluctuations in blood pressure. Calibration lines correspond to pressure values ​​of 100 and 150 mmHg. Art.

Recording Electrical Potentials B shows continuous frequent impulses that occur when chemoreceptors are irritated by a lack of oxygen. High-amplitude potentials during periods of pulse increases in blood pressure are caused by impulses of the pressoreceptors of the carotid sinus.

The fact that the irritant of chemoreceptors is a decrease in oxygen tension in the blood plasma, and not a decrease in its total content in the blood, is proven by the following observations of L. L. Shik. When the amount of hemoglobin decreases or when it is bound by carbon monoxide, the oxygen content in the blood is sharply reduced, but the dissolution of O 2 in the blood plasma is not impaired and its tension in the plasma remains normal. In this case, the chemoreceptors are not excited and breathing does not change, although oxygen transport is sharply impaired and the tissues experience a state of oxygen starvation, since not enough oxygen is delivered to them by hemoglobin. When atmospheric pressure decreases, when the oxygen tension in the blood decreases, chemoreceptors are excited and breathing increases.

The nature of changes in breathing with an excess of carbon dioxide and a decrease in oxygen tension in the blood is different. With a slight decrease in oxygen tension in the blood, a reflex increase in the breathing rhythm is observed, and with a slight increase in carbon dioxide tension in the blood, a reflex deepening of respiratory movements occurs.

Thus, the activity of the respiratory center is regulated by the effect of an increased concentration of H + ions and increased CO 2 tension on the chemoreceptors of the medulla oblongata and on the chemoreceptors of the carotid and aortic bodies, as well as the effect on the chemoreceptors of these vascular reflexogenic zones of decreased oxygen tension in the arterial blood.

Causes of a newborn's first breath are explained by the fact that in the womb, gas exchange of the fetus occurs through the umbilical vessels, which are in close contact with the maternal blood in the placenta. The cessation of this connection with the mother at birth leads to a decrease in oxygen tension and the accumulation of carbon dioxide in the blood of the fetus. This, according to Barcroft, irritates the respiratory center and leads to inhalation.

For the first breath to occur, it is important that the cessation of embryonic respiration occurs suddenly: when the umbilical cord is slowly clamped, the respiratory center is not excited and the fetus dies without taking a single breath.

It should also be taken into account that the transition to new conditions causes irritation of a number of receptors in the newborn and the flow of impulses through the afferent nerves, increasing the excitability of the central nervous system, including the respiratory center (I. A. Arshavsky).

The importance of mechanoreceptors in the regulation of breathing. The respiratory center receives afferent impulses not only from chemoreceptors, but also from pressoreceptors of the vascular reflexogenic zones, as well as from mechanoreceptors of the lungs, respiratory tract and respiratory muscles.

The influence of pressoreceptors of vascular reflexogenic zones is found in the fact that an increase in pressure in the isolated carotid sinus, connected to the body only by nerve fibers, leads to inhibition of respiratory movements. This also happens in the body when blood pressure rises. On the contrary, when blood pressure decreases, breathing becomes faster and deeper.

Impulses coming to the respiratory center via the vagus nerves from the lung receptors are important in the regulation of breathing. The depth of inhalation and exhalation largely depends on them. The presence of reflex influences from the lungs was described in 1868 by Hering and Breuer and formed the basis for the idea of ​​reflex self-regulation of breathing. It manifests itself in the fact that when you inhale, impulses arise in the receptors located in the walls of the alveoli, reflexively inhibiting inhalation and stimulating exhalation, and with a very sharp exhalation, with an extreme degree of decrease in lung volume, impulses arise that arrive to the respiratory center and reflexively stimulate inhalation . The presence of such reflex regulation is evidenced by the following facts:

In the lung tissue in the walls of the alveoli, i.e. in the most extensible part of the lung, there are interoreceptors, which are the perceiving irritations of the endings of the afferent fibers of the vagus nerve;

After cutting the vagus nerves, breathing becomes sharply slower and deeper;

When the lung is inflated with an indifferent gas, for example nitrogen, under the obligatory condition that the vagus nerves are intact, the muscles of the diaphragm and intercostal spaces suddenly stop contracting, and inhalation stops before reaching the usual depth; on the contrary, when air is artificially suctioned from the lung, the diaphragm contracts.

Based on all these facts, the authors came to the conclusion that stretching of the pulmonary alveoli during inhalation causes irritation of the lung receptors, as a result of which the impulses coming to the respiratory center through the pulmonary branches of the vagus nerves become more frequent, and this reflexively excites the expiratory neurons of the respiratory center, and, consequently, entails the occurrence of exhalation. Thus, as Hering and Breuer wrote, “every breath, as it stretches the lungs, itself prepares its end.”

If you connect the peripheral ends of the cut vagus nerves to an oscilloscope, you can record action potentials that arise in the receptors of the lungs and travel along the vagus nerves to the central nervous system not only when the lungs are inflated, but also when air is artificially suctioned from them. During natural breathing, frequent currents of action in the vagus nerve are detected only during inhalation; during natural exhalation they are not observed (Figure 4).

Figure 4 - Currents of action in the vagus nerve during stretching of the lung tissue during inhalation (according to Adrian) From top to bottom: 1 - afferent impulses in the vagus nerve: 2 - recording of breathing (inhalation - up, exhalation - down); 3 - timestamp

Consequently, the collapse of the lungs causes reflex irritation of the respiratory center only with such strong compression of them, which does not happen during normal, ordinary exhalation. This is observed only with a very deep exhalation or sudden bilateral pneumothorax, to which the diaphragm reflexively reacts by contracting. During natural breathing, the receptors of the vagus nerves are stimulated only when the lungs are stretched and reflexively stimulate exhalation.

In addition to the mechanoreceptors of the lungs, mechanoreceptors of the intercostal muscles and the diaphragm take part in the regulation of breathing. They are excited by stretching during exhalation and reflexively stimulate inhalation (S.I. Frankstein).

Relationships between inspiratory and expiratory neurons of the respiratory center. There are complex reciprocal (conjugate) relationships between inspiratory and expiratory neurons. This means that excitation of inspiratory neurons inhibits expiratory ones, and excitation of expiratory neurons inhibits inspiratory ones. Such phenomena are partly due to the presence of direct connections that exist between the neurons of the respiratory center, but mainly they depend on reflex influences and on the functioning of the pneumotaxis center.

The interaction between neurons of the respiratory center is currently represented as follows. Due to the reflex (through chemoreceptors) action of carbon dioxide on the respiratory center, excitation of inspiratory neurons occurs, which is transmitted to the motor neurons innervating the respiratory muscles, causing the act of inhalation. At the same time, impulses from the inspiratory neurons arrive at the pneumotaxis center located in the pons, and from it, along the processes of its neurons, impulses arrive at the expiratory neurons of the respiratory center of the medulla oblongata, causing excitation of these neurons, cessation of inhalation and stimulation of exhalation. In addition, excitation of expiratory neurons during inhalation is also carried out reflexively through the Hering-Breuer reflex. After transection of the vagus nerves, the flow of impulses from the mechanoreceptors of the lungs stops and expiratory neurons can be excited only by impulses coming from the pneumotaxis center. The impulse stimulating the exhalation center is significantly reduced and its stimulation is somewhat delayed. Therefore, after cutting the vagus nerves, inhalation lasts much longer and is replaced by exhalation later than before cutting the nerves. Breathing becomes rare and deep.

Similar changes in breathing with intact vagus nerves occur after transection of the brainstem at the level of the pons, separating the pneumotaxis center from the medulla oblongata (see Figure 1, Figure 5). After such a transection, the flow of impulses stimulating the exhalation center also decreases, and breathing becomes rare and deep. In this case, the exhalation center is excited only by impulses reaching it via the vagus nerves. If in such an animal the vagus nerves are also transected or the propagation of impulses along these nerves is interrupted by cooling them, then excitation of the exhalation center does not occur and breathing stops in the phase of maximum inspiration. If after this the conductivity of the vagus nerves is restored by warming them, then excitation of the exhalation center periodically occurs again and rhythmic breathing is restored (Figure 6).

Figure 5 - Diagram of nerve connections of the respiratory center 1 - inspiratory center; 2 - pneumotaxis center; 3 - expiratory center; 4 - mechanoreceptors of the lung. After moving along the lines / and // separately, the rhythmic activity of the respiratory center is preserved. With simultaneous cutting, breathing stops during the inhalation phase.

Thus, the vital function of breathing, possible only with the rhythmic alternation of inhalation and exhalation, is regulated by a complex nervous mechanism. When studying it, attention is drawn to the multiple support for the operation of this mechanism. Excitation of the inspiratory center occurs both under the influence of an increase in the concentration of hydrogen ions (increased CO 2 tension) in the blood, causing excitation of the chemoreceptors of the medulla oblongata and chemoreceptors of the vascular reflexogenic zones, and as a result of the influence of reduced oxygen tension on the aortic and carotid chemoreceptors. Excitation of the exhalation center is caused by both reflex impulses coming to it via the afferent fibers of the vagus nerves, and the influence of the inhalation center, carried out through the pneumotaxis center.

The excitability of the respiratory center changes under the action of nerve impulses arriving along the cervical sympathetic nerve. Irritation of this nerve increases the excitability of the respiratory center, which intensifies and speeds up breathing.

The influence of sympathetic nerves on the respiratory center partly explains changes in breathing during emotions.

Figure 6 - The effect of turning off the vagus nerves on breathing after cutting the brain at the level between the lines I and II(see Figure 5) (by Stella) A- recording of breathing; b- nerve cooling mark

1) oxygen

3) carbon dioxide

5) adrenaline

307. Central chemoreceptors involved in the regulation of respiration are localized

1) in the spinal cord

2) in the pons

3) in the cerebral cortex

4) in the medulla oblongata

308. Peripheral chemoreceptors involved in the regulation of respiration are mainly localized

1) in the organ of Corti, aortic arch, carotid sinus

2) in the capillary bed, aortic arch

3) in the aortic arch, carotid sinus

309. Hyperpnea after voluntary breath holding occurs as a result

1) reducing CO2 tension in the blood

2) decrease in O2 tension in the blood

3) an increase in O2 tension in the blood

4) an increase in CO2 tension in the blood

310. Physiological significance of the Hering-Breuer reflex

1) in stopping inhalation during protective respiratory reflexes

2) in an increase in respiratory rate with increasing body temperature

3) in regulating the ratio of depth and frequency of breathing depending on lung volume

311. Contractions of the respiratory muscles stop completely

1) when separating the pons from the medulla oblongata

2) with bilateral transection of the vagus nerves

3) when the brain is separated from the spinal cord at the level of the lower cervical segments

4) when the brain is separated from the spinal cord at the level of the upper cervical segments

312. The cessation of inhalation and the beginning of exhalation is due primarily to the influence of receptors

1) chemoreceptors of the medulla oblongata

2) chemoreceptors of the aortic arch and carotid sinus

3) irritant

4) juxtacapillary

5) stretched lungs

313. Dyspnea (shortness of breath) occurs

1) when inhaling gas mixtures with a high (6%) carbon dioxide content

2) weakening of breathing and stopping it

3) insufficiency or difficulty breathing (heavy muscular work, pathology of the respiratory system).

314. Gas homeostasis in high altitude conditions is maintained due to

1) decreased oxygen capacity of the blood

2) decrease in heart rate

3) decrease in breathing rate

4) increase in the number of red blood cells

315. Normal inhalation is ensured by contraction

1) internal intercostal muscles and diaphragm

2) internal and external intercostal muscles

3) external intercostal muscles and diaphragm

316. Contractions of the respiratory muscles completely stop after transection of the spinal cord at the level

1) lower cervical segments

2) lower thoracic segments

3) upper cervical segments

317. Increased activity of the respiratory center and increased ventilation of the lungs causes

1) hypocapnia

2) normocapnia

3) hypoxemia

4) hypoxia

5) hypercapnia

318. An increase in pulmonary ventilation, which is usually observed when rising to a height of more than 3 km, leads to

1) to hyperoxia

2) to hypoxemia

3) to hypoxia

4) to hypercapnia

5) to hypocapnia

319. The receptor apparatus of the carotid sinus controls the gas composition

1) cerebrospinal fluid

2) arterial blood entering the systemic circulation

3) arterial blood entering the brain

320. The gas composition of the blood entering the brain controls the receptors

1) bulbar

2) aortic

3) carotid sinuses

321. The gas composition of the blood entering the systemic circulation controls the receptors

1) bulbar

2) carotid sinuses

3) aortic

322. Peripheral chemoreceptors of the carotid sinus and aortic arch are sensitive, mainly

1) to an increase in O2 and CO2 voltage, a decrease in blood pH

2) to an increase in O2 voltage, a decrease in CO2 tension, an increase in blood pH

3) reducing O2 and Co2 tension, increasing blood pH

4) decrease in O2 voltage, increase in CO2 voltage, decrease in blood pH

DIGESTION

323. What components of food and products of its digestion enhance intestinal motility?(3)

· Black bread

· White bread

324. What is the main role of gastrin:

Activates pancreatic enzymes

Converts pepsinogen to pepsin in the stomach

Stimulates the secretion of gastric juice

· Inhibits pancreatic secretion

325. What is the reaction of saliva and gastric juice during the digestion phase:

· pH of saliva 0.8-1.5, pH of gastric juice 7.4-8.

Saliva pH 7.4-8.0, gastric juice pH 7.1-8.2

Saliva pH 5.7-7.4, gastric juice pH 0.8-1.5

saliva pH 7.1-8.2, gastric juice pH 7.4-8.0

326. The role of secretin in the digestion process:

· Stimulates the secretion of HCI.

· Inhibits bile secretion

Stimulates the secretion of pancreatic juice

327. How do the following substances affect the motility of the small intestine?

Adrenaline enhances, acetylcholine inhibits

Adrenaline inhibits, acetylcholine enhances

Adrenaline has no effect, acetylcholine enhances

Adrenaline inhibits, acetylcholine has no effect

328. Fill in the missing words, choosing the most correct answers.

Stimulation of parasympathetic nerves ....................... the amount of saliva secretion with ………………………… concentration of organic compounds.

Increases, low

· Reduces, high

· Increases, high.

· Reduces, low

329. Under the influence of what factor do insoluble fatty acids turn into soluble fatty acids in the digestive tract:

Under the influence of pancreatic juice lipase

Under the influence of gastric juice lipase

Under the influence of bile acids

Under the influence of hydrochloric acid of gastric juice

330. What causes swelling of proteins in the digestive tract:

Bicarbonates

Hydrochloric acid

· Intestinal juice

331. Name which of the substances listed below are natural endogenous stimulants of gastric secretion. Choose the most correct answer:

Histamine, gastrin, secretin

Histamine, gastrin, enterogastrin

Histamine, hydrochloric acid, enterokinase

· Gastrin, hydrochloric acid, secretin

11. Will glucose be absorbed in the intestine if its concentration in the blood is 100 mg%, and in the intestinal lumen is 20 mg%:

· There won't be

12. How will intestinal motor function change if atropine is administered to a dog:

· Bowel motor function will not change

There is a weakening of intestinal motor function

There is an increase in intestinal motor function

13. What substance, when introduced into the blood, causes inhibition of the secretion of hydrochloric acid in the stomach:

Gastrin

· Histamine

· Secretin

Products of protein digestion

14. Which of the following substances enhances the movement of intestinal villi:

· Histamine

· Adrenaline

· Willikinin

· Secretin

15. Which of the following substances enhances gastric motility:

Gastrin

Enterogastron

Cholecystokinin-pancreozymin

16. Select from the substances listed below the hormones that are produced in the duodenum:

· Secretin, thyroxine, villikinin, gastrin

· Secretin, enterogastrin, villikinin, cholecystokinin

· Secretin, enterogastrin, glucagon, histamine

17. Which option comprehensively and correctly lists the functions of the gastrointestinal tract?

Motor, secretory, excretory, absorption

Motor, secretory, absorption, excretory, endocrine

Motor, secretory, absorption, endocrine

18. Gastric juice contains enzymes:

· Peptidases

Lipase, peptidases, amylase

· Proteases, lipase

· Proteases

19. An involuntary act of defecation is carried out with the participation of a center located:

In the medulla oblongata

In the thoracic spinal cord

In the lumbosacral spinal cord

In the hypothalamus

20. Choose the most correct answer.

Pancreatic juice contains:

Lipase, peptidase

Lipase, peptidase, nuclease

Lipase, peptidase, protease, amylase, nuclease, elastase

Elastase, nuclease, peptidase

21. Choose the most correct answer.

Sympathetic nervous system:

· Inhibits gastrointestinal motility

· Inhibits secretion and motility of the gastrointestinal tract

· Inhibits gastrointestinal secretion

· Activates motility and secretion of the gastrointestinal tract

· Activates gastrointestinal motility

23. The flow of bile into the duodenum is limited. This will result:

Impaired protein breakdown

Impaired carbohydrate breakdown

To inhibition of intestinal motility

· Impaired fat breakdown

25. The centers of hunger and satiety are located:

· In the cerebellum

In the thalamus

In the hypothalamus

29. Gastrin is formed in the mucous membrane:

Body and fundus of the stomach

· Antrum

Greater curvature

30. Gastrin stimulates mainly:

Main cells

· Mucous cells

Parietal cells

33. Motility of the gastrointestinal tract is stimulated by:

Parasympathetic nervous system

Sympathetic nervous system

So far we have discussed the basic mechanisms that cause the occurrence of inhalation and exhalation, but it is equally important to know how the intensity of the signals that regulate ventilation changes depending on the needs of the body. For example, during heavy physical work, the rate of oxygen consumption and carbon dioxide production often increases 20 times compared to rest, requiring a corresponding increase in ventilation. The rest of this chapter is devoted to the regulation of ventilation depending on the level of demand of the body.

The highest purpose of breathing is to preserve proper oxygen concentrations, carbon dioxide and hydrogen ions in tissues. Fortunately, respiratory activity is very sensitive to changes in these parameters.

Excess dioxide carbon or hydrogen ions in the blood acts mainly directly on the respiratory center, causing a significant increase in inspiratory and expiratory motor signals to the respiratory muscles.

Oxygen, on the contrary, has no significant direct influence on the cerebral respiratory center to regulate breathing. Instead, it acts predominantly on peripheral chemoreceptors located in the carotid and aortic bodies, which, in turn, transmit appropriate signals along the nerves to the respiratory center to regulate breathing at this level.
Let us first discuss the stimulation of the respiratory center by carbon dioxide and hydrogen ions.

Chemosensitive zone of the respiratory center. Until now, we have mainly considered the functions of three zones of the respiratory center: the dorsal group of respiratory neurons, the ventral group of respiratory neurons and the pneumotaxic center. These zones are not thought to be directly affected by changes in carbon dioxide or hydrogen ion concentrations. There is an additional zone of neurons, the so-called chemosensitive zone, which is located bilaterally and lies under the ventral surface of the medulla oblongata at a depth of 0.2 mm. This zone is highly sensitive to both changes in Pco2 and changes in the concentration of hydrogen ions and, in turn, excites other parts of the respiratory center.

Sensory neurons of the chemosensitive zone particularly sensitive to hydrogen ions; It is believed that hydrogen ions may be the only direct stimulus important for these neurons. But hydrogen ions do not easily cross the barrier between the blood and the brain, so changes in the concentration of hydrogen ions in the blood have much less ability to stimulate chemosensitive neurons than changes in the concentration of carbon dioxide in the blood, despite the fact that carbon dioxide stimulates these neurons indirectly by first causing a change concentration of hydrogen ions.

Direct stimulating carbon dioxide effect on the neurons of the chemosensitive zone is insignificant, but it has a powerful indirect effect. After water combines with carbon dioxide, carbonic acid is formed in the tissues, which dissociates into hydrogen and bicarbonate ions; Hydrogen ions have a powerful direct stimulating effect on breathing.

Contained carbon dioxide in the blood stimulates chemosensitive neurons more strongly than hydrogen ions located there, since the barrier between the blood and the brain is poorly permeable to hydrogen ions, and carbon dioxide passes through it almost unhindered. Consequently, as soon as Pco2 increases in the blood, it increases both in the interstitial fluid of the medulla oblongata and in the cerebrospinal fluid. In these liquids, carbon dioxide immediately reacts with water to create new hydrogen ions. A paradox results: with an increase in the concentration of carbon dioxide in the blood, more hydrogen ions appear in the chemosensitive respiratory zone of the medulla oblongata than with an increase in the concentration of hydrogen ions in the blood. As a result, as the concentration of carbon dioxide in the blood increases, the activity of the respiratory center will change dramatically. Next we will return to a quantitative analysis of this fact.

Decrease in stimulant effects of carbon dioxide after the first 1-2 days. Stimulation of the respiratory center by carbon dioxide is great in the first few hours of the initial increase in its concentration, and then over the next 1-2 days it gradually decreases to 1/5 of the initial rise. Part of this decrease is caused by the work of the kidneys, which strive to normalize this indicator after the initial increase in the concentration of hydrogen ions (due to an increase in the concentration of carbon dioxide).

To do this, the kidneys work in the direction of increasing amount of bicarbonates in the blood, which attach to hydrogen ions in the blood and cerebrospinal fluid, thus reducing the concentration of hydrogen ions in them. Even more significant is the fact that after a few hours, bicarbonate ions slowly diffuse through the barriers between the blood and brain, blood and cerebrospinal fluid, and combine with hydrogen ions immediately near the respiratory neurons, reducing the concentration of hydrogen ions to almost normal. Thus, a change in the concentration of carbon dioxide has a powerful immediate regulatory effect on the impulse of the respiratory center, and the long-term effect after some days of adaptation will be weak.

In the figure with approximate accuracy shows the influence of Pco2 and blood pH for alveolar ventilation. Note the pronounced increase in ventilation due to an increase in Pco2 in the normal range between 35 and 75 mm Hg. Art.

This demonstrates great importance changes in carbon dioxide concentration in the regulation of breathing. In contrast, a change in blood pH in the normal range of 7.3-7.5 causes a change in respiration that is 10 times smaller.

Respiratory center called a set of nerve cells located in different parts of the central nervous system, ensuring the coordinated rhythmic activity of the respiratory muscles and adaptation of breathing to the changing conditions of the external and internal environment of the body.

Some groups of nerve cells are essential for the rhythmic activity of the respiratory muscles. They are located in the reticular formation of the medulla oblongata, making up respiratory center in the narrow sense of the word. Impaired function of these cells leads to cessation of breathing due to paralysis of the respiratory muscles.

Innervation of the respiratory muscles . The respiratory center of the medulla oblongata sends impulses to motor neurons located in the anterior horns of the gray matter of the spinal cord, innervating the respiratory muscles.

Motor neurons, the processes of which form the phrenic nerves innervating the diaphragm, are located in the anterior horns of the 3-4th cervical segments. Motor neurons, the processes of which form the intercostal nerves that innervate the intercostal muscles, are located in the anterior horns of the thoracic spinal cord. From this it is clear that when the spinal cord is transected between the thoracic and cervical segments, costal breathing stops, and diaphragmatic breathing is preserved, since the motor nucleus of the phrenic nerve, located above the transection, maintains connection with the respiratory center and the diaphragm. When the spinal cord is cut under the medulla oblongata, breathing stops completely and the body dies from suffocation. With such a transection of the brain, however, contractions of the auxiliary respiratory muscles of the nostrils and larynx, which are innervated by nerves emerging directly from the medulla oblongata, continue for some time.

Localization of the respiratory center . Already in ancient times it was known that damage to the spinal cord below the medulla oblongata leads to death. In 1812, Legallois, by cutting the brains of birds, and in 1842, Flourens, by irritating and destroying parts of the medulla oblongata, explained this fact and provided experimental evidence of the location of the respiratory center in the medulla oblongata. Flourens envisioned the respiratory center as a limited area the size of a pinhead and gave it the name “vital node.”

N. A. Mislavsky in 1885, using the technique of point irritation and destruction of individual sections of the medulla oblongata, established that the respiratory center is located in the reticular formation of the medulla oblongata, in the region of the bottom of the IV ventricle, and is paired, with each half innervating the respiratory muscles the same half of the body. In addition, N.A. Mislavsky showed that the respiratory center is a complex formation consisting of an inhalation center (inspiratory center) and an exhalation center (expiratory center).

He came to the conclusion that a certain area of ​​the medulla oblongata is a center that regulates and coordinates respiratory movements. N. A. Mislavsky’s conclusions are confirmed by numerous experiments and studies, in particular those carried out recently using microelectrode technology. When recording the electrical potentials of individual neurons of the respiratory center, it was discovered that there are neurons in it whose discharges sharply become more frequent during the inhalation phase, and other neurons whose discharges become more frequent during the exhalation phase.

Stimulation of individual points of the medulla oblongata with electric current, carried out using microelectrodes, also revealed the presence of neurons, the stimulation of which causes the act of inhalation, and other neurons, the stimulation of which causes the act of exhalation. Baumgarten showed in 1956 that the neurons of the respiratory center are distributed in the reticular formation of the medulla oblongata, near the striae acusticac ( rice. 61). There is an exact boundary between expiratory and inspiratory neurons, but there are areas where one of them predominates (inspiratory - in the caudal section of the solitary fascicle tractus solitarius, expiratory - in the ventral nucleus - nucleus ambiguus). Rice. 61. Localization of respiratory centers.

Lumsden and other researchers, in experiments on warm-blooded animals, found that the respiratory center has a more complex structure than previously thought. In the upper part of the pons there is a so-called pneumotaxic center, which controls the activity of the lower respiratory centers of inhalation and exhalation and ensures normal respiratory movements. The significance of the pneumotaxic center is that during inhalation it causes excitation of the exhalation center and, thus, ensures rhythmic alternation and exhalation.

The activity of the entire set of neurons that form the respiratory center is necessary to maintain normal breathing. However, the overlying parts of the central nervous system also take part in the processes of breathing regulation, which provide adaptive changes in breathing during various types of body activity. An important role in the regulation of breathing belongs to the cerebral hemispheres and their cortex, thanks to which the adaptation of respiratory movements during talking, singing, sports and human work is carried out.

The picture shows the lower part of the brain stem (rear view). PN - pneumotaxis center; INSP - inspiratory; EXP - expiratory centers. The centers are double-sided, but to simplify the diagram, only one of the centers is shown on each side. Cutting above line 1 does not affect breathing. Cutting along line 2 separates the pneumotaxis center. Cutting below line 3 causes cessation of breathing.

Automation of the respiratory center . The neurons of the respiratory center are characterized by rhythmic automaticity. This is evident from the fact that even after the afferent impulses coming to the respiratory center are completely turned off, rhythmic oscillations of biopotentials arise in its neurons, which can be recorded with an electrical measuring device. This phenomenon was first discovered back in 1882 by I.M. Sechenov. Much later, Adrian and Butendijk, using an oscilloscope with an amplifier, recorded rhythmic fluctuations in electrical potentials in the isolated brain stem of a goldfish. B. D. Kravchinsky observed similar rhythmic oscillations of electrical potentials occurring in the rhythm of breathing in the isolated medulla oblongata of a frog.

The automatic excitation of the respiratory center is due to the metabolic processes occurring within it and its high sensitivity to carbon dioxide. The automation of the center is regulated by nerve impulses coming from the receptors of the lungs, vascular reflexogenic zones, respiratory and skeletal muscles, as well as impulses from the overlying parts of the central nervous system and, finally, humoral influences.

Respiratory system. Breath.

A) does not change B) narrows C) expands

2. Number of cell layers in the wall of the pulmonary vesicle:
A) 1 B) 2 C) 3 D) 4

3. Shape of the diaphragm during contraction:
A) flat B) domed C) elongated D) concave

4. The respiratory center is located in:
A) medulla oblongata B) cerebellum C) diencephalon D) cerebral cortex

5. Substance that causes activity of the respiratory center:
A) oxygen B) carbon dioxide C) glucose D) hemoglobin

6. A section of the tracheal wall that lacks cartilage:
A) front wall B) side walls C) rear wall

7. The epiglottis closes the entrance to the larynx:
A) during a conversation B) when inhaling C) when exhaling D) when swallowing

8. How much oxygen is contained in exhaled air?
A) 10% B) 14% C) 16% D) 21%

9. An organ that does not participate in the formation of the wall of the chest cavity:
A) ribs B) sternum C) diaphragm D) pericardial sac

10. Organ that does not line the pleura:
A) trachea B) lung C) sternum D) diaphragm E) ribs

11. The Eustachian tube opens at:
A) nasal cavity B) nasopharynx C) pharynx D) larynx

12. The pressure in the lungs is greater than the pressure in the pleural cavity:
A) when inhaling B) when exhaling C) in any phase D) when holding your breath while inhaling

14. The walls of the larynx are formed:
A) cartilage B) bones C) ligaments D) smooth muscles

15. How much oxygen is contained in the air of the lung vesicles?
A) 10% B) 14% C) 16% D) 21%

16. The amount of air that enters the lungs during a quiet inhalation:
A) 100-200 cm 3 B) 300-900 cm 3 C) 1000-1100 cm 3 D) 1200-1300 cm 3

17. The membrane that covers the outside of each lung:
A) fascia B) pleura C) capsule D) basement membrane

18. During swallowing occurs:
A) inhale B) exhale C) inhale and exhale D) hold your breath

19 . Amount of carbon dioxide in atmospheric air:
A) 0.03% B) 1% C) 4% D) 6%

20. Sound is formed when:

A) inhale B) exhale C) hold your breath while inhaling D) hold your breath while exhaling

21. Does not take part in the formation of speech sounds:
A) trachea B) nasopharynx C) pharynx D) mouth E) nose

22. The wall of the pulmonary vesicles is formed by tissue:
A) connective B) epithelial C) smooth muscle D) striated muscle

23. Shape of the diaphragm when relaxed:
A) flat B) elongated C) dome-shaped D) concave into the abdominal cavity

24. Amount of carbon dioxide in exhaled air:
A) 0.03% B) 1% C) 4% D) 6%

25. Airway epithelial cells contain:
A) flagella B) villi C) pseudopods D) cilia

26 . The amount of carbon dioxide in the air of the pulmonary bubbles:
A) 0.03% B) 1% C) 4% D) 6%

28. With an increase in chest volume, pressure in the alveoli:
A) does not change B) decreases C) increases

29 . Amount of nitrogen in atmospheric air:
A) 54% B) 68% C) 79% D) 87%

30. Outside the chest is located:
A) trachea B) esophagus C) heart D) thymus (thymus gland) E) stomach

31. The most frequent respiratory movements are characteristic of:
A) newborns B) children 2-3 years old C) teenagers D) adults

32. Oxygen moves from the alveoli to the blood plasma when:

A) pinocytosis B) diffusion C) respiration D) ventilation

33 . Number of breathing movements per minute:
A) 10-12 B) 16-18 C) 2022 D) 24-26

34 . A diver develops gas bubbles in his blood (the cause of decompression sickness) when:
A) slow rise from depth to the surface B) slow descent to depth

C) rapid ascent from depth to the surface D) rapid descent to depth

35. Which laryngeal cartilage protrudes forward in men?
A) epiglottis B) arytenoid C) cricoid D) thyroid

36. The causative agent of tuberculosis belongs to:
A) bacteria B) fungi C) viruses D) protozoa

37. Total surface of the pulmonary vesicles:
A) 1 m 2 B) 10 m 2 C) 100 m 2 D) 1000 m 2

38. The concentration of carbon dioxide at which poisoning begins in a person:

39 . The diaphragm first appeared in:
A) amphibians B) reptiles C) mammals D) primates E) humans

40. The concentration of carbon dioxide at which a person experiences loss of consciousness and death:

A) 1% B) 2-3% C) 4-5% D) 10-12%

41. Cellular respiration occurs in:
A) nucleus B) endoplasmic reticulum C) ribosome D) mitochondria

42. The amount of air for an untrained person during a deep breath:
A) 800-900 cm 3 B) 1500-2000 cm 3 C) 3000-4000 cm 3 D) 6000 cm 3

43. The phase when the lung pressure is above atmospheric:
A) inhale B) exhale C) inhale hold D) exhale hold

44. Pressure that begins to change during breathing earlier:
A) in the alveoli B) in the pleural cavity C) in the nasal cavity D) in the bronchi

45. A process that requires the participation of oxygen:
A) glycolysis B) protein synthesis C) fat hydrolysis D) cellular respiration

46. The airways do not include the organ:
A) nasopharynx B) larynx C) bronchi D) trachea E) lungs

47 . Does not apply to the lower respiratory tract:

A) larynx B) nasopharynx C) bronchi D) trachea

48. The causative agent of diphtheria is classified as:
A) bacteria B) viruses C) protozoa D) fungi

49. Which component of exhaled air is found in greater quantities?

A) carbon dioxide B) oxygen C) ammonia D) nitrogen E) water vapor

50. The bone in which the maxillary sinus is located?
A) frontal B) temporal C) maxillary D) nasal

Answers: 1b, 2a, 3a, 4a, 5b, 6c, 7d, 8c, 9d, 10a, 11b, 12c, 13c, 14a, 15b, 16b, 17b, 18d, 19a, 20b, 21a, 22b, 23c, 24c, 25g, 26g, 27c, 28b, 29c, 30g, 31a, 32b, 33b, 34c, 35g, 36a, 37c, 38c, 39c, 40g, 41g, 42c, 43b, 44a, 45g, 46d, 47b, 48a, g, 50v