Respiration physiology. External respiration. Gas transition and transfer by blood.

 

Respiration is vitally essential for human beings and animals life. Respiration is gas exchange between organism external and internal environment. This process is performed in several stages:

1) External or lung respiration – performes gas exchange between organism external and internal environment (between air and blood).

2) Gas transition and transfer – is performed due to alveoles permeability and blood transport function.

3) Internal or tissular respiration – performes directly cellular oxidation process.

External respiration – is performed with cycles change, one respiratory act consists of inspiration and expiration phases. As a rule, inspiration is shorter than expiration. Inspiration act: thorax volume increases in 3 directions – vertical, sagittal and frontal. Why? There are some reasons:

· Diaphragm contraction (if diaphragm in rest state is shifted on 1 cm it leads to thorax increasing on 200-300 ml of air). Result of diaphragm contraction: decreasing (flattening) of its cupula; visceral organs (in abdominal cavity) pushing down, throrax increasing in vertical direction.

· Contraction of external oblique intercostal and intercartillaginous muscles: they are fixed to above-lied rib near spinal cord, to below-lied rib – near sternum. Result: throrax volume increasing in sagittal and frontal directions. Ribs are putted forward, up and towards. And it supports such lungs localization change.

· As lungs are connected with thorax through pleura visceral and parietal layers then lungs volume increasing occurs after thorax volume rising up. It leads to pressure decreasing in them. Pressure becomes lower than atmospheric one, air comes into lungs. Thus, negative pressure is third reason (factor).

· This negative pressure increases in course of inspiration because at lungs stretching their elastic draft - force with which lung strives for compression - is increased. Elastic draft is explained by 2 factors: there are many elastic fibres in alveoles walls - the first one – and the existance of surface tension of liquid tunic containing surfactants and covering alveole wall internal surface – the second one. Elastic draft (the 4-th factor of inspiration) is increased in course of inspiration, negative pressure is rised up in pleural cavity that encourages inspiration act.

Thus, inspiration is rather active process.

Expiration act – under usual conditions is performed passively by means of following factors:

· thorax gravity force;

· elastic graft of rib cartillages overwinded in course of inspiration;

· abdominal cavity organs pressure.

But expiration as inspiration may be also active (for instance, at hyperventillation, cough, someone’s straining and so on), when internal intercostal muscles contraction occurs. These muscles are fixed near spinal cord to below-lied rib and near sternum to above-lied rib and their contraction cause pushing ribs down, ahead and inside.

Respiratory muscles in course of their activity passe through some resistance, 2/3 of which is elastic, defined by lungs and thorax tissues as well as surfactant action; 1/3 – non-elastic caused by gas stream friction with air ways.

Negative pressure appearence in pleural fissure is explained by following fact: new-born thorax grows faster than lungs that’s why lung tissue is undergone to constant tension. Pleural layers possess large absorbtive ability that encourages negative pressure creation. That’s why gas introducing in pleural cavity is absorbed after some time and negative pressure is restored in pleural cavity. Thus, negative pressure is constantly supported in pleural cavity. If thorax is wounded than pressure in pleural fissure becomes equal to atmospheric one and lung is falling down, pneumothorax occurs. If we have liquid, blood and pus – the names will be correspondingly hydrothorax, haemathorax and pyothorax.

 

One can differentiate 2 main respiration types:

1) Thoracic (rib) – thorax dilation is connected mainly with ribs rising; respiration is mainly performed by means of intercostal muscles activity, diaphragm is moved passively according to interthoracic pressure change. This respiration type is a female.

2) Abdominal (phrenic or diaphragmal) – diaphragm contraction (flattening) is main respiration factor as the result of which interpleural pressure is decreased and simultaneousely interabdominal pressure is increased. This respiration type is more effective because lungs are ventillated in more extent and stronger in course of it and blood venous return is released from abdominal cavity organs to heart. Diaphragmal respiration is more physiological! It is called male respiration. There exists one important rule for women: they must breath with thorax mainly only when their pregnancy!

Air amount in lungs after maximal inspiration is known as common lungs capacity (CLC). It is 4200-6000 ml in adults. Its compounds are: vital lung capacity (VLC) and residual volume (RV). VLC – air amount which leaves lungs in course of maximally deep expiration after maximally deep inspiration. It is equal to 3300-4800 ml under norma (in males 4000-4800 ml, in females – 3300-4000 ml). VLC consists of 3 lung volumes:

1) respirational volume (RV) of air inspirated and expirated in course of each respiratory cycle under rest state – 400-500 ml;

2) reserve inspiration volume – additional air that one can inspirate in course of maximal inspiration after usual inspiration – 1900-3300 ml;

3) reserve expiration volume – additional air that one can expirate in course of maximal expiration after usual expiration – 700-1000 ml.

At usual respiration we have reserve expiration volume and respirational volume in our lungs.

Residual volume – everything that is in lungs after deep inspiration - it is equal to 1200-2000 ml. It is in our lungs even after death!

There exists one more volume – harmful space volume – air part that is remained in air ways (nasal ducts, oral cavity, nasopharynx, nasal additional sinuses, trachea, bronchi) and doesn’t reach lungs (this air doesn’t participate in gas exchange). Such anatomical space is about 140-200 ml. It very useful despite its name “harmful” because air passing through them (especially when its passage through nasal ducts) becomes warm, humid, protected from side particles, bacterias. Respiration through nose is more physiological!

For 1 minute, at respiration freaquency equal to 16-20, one inspirates volume that has name of minute volume (MV). Its size depends on 2 compounds: respiration volume and respiration freaquency. Respiration freaquency 16-20 (norma indicated in all textbooks and manuals) per 1 minute is not ideally physiological. Less respiration freaquency which may be reached by corresponding training (the most often – physical training) - is more physiologic from the point of view delt with diseases prevention not only in respiratory appatarus but also in other organs and systems. Why less respiration freaquency is more physiological? Describe these advantages on concrete example of trained person respiration. Imagine, please, 2 people before us, of equal constitution, but one of them is regularly done some kind of physical activity (regular morning exercise, running and so on). Respirational volume is always higher in trained person in comparison with untrained. Example. Respirational volume in trained person – 800 ml; in untrained - 400 ml. After small physical loading their respiration freaquency is getting increased: in trained person – to 20 respiratory acts per minute, in untrained – rather higher (for example, 40). At such ziphras minute volume in both people will be equal to 16000 ml of air (400 ml x 40 and 800 ml x 20). In what are the advantages of one of them before other? In the first human being (trained) from 800 ml of respiratory volume 600 ml will come to alveoles with every inspiration (if both subjects have harmful space volume equal to 200 ml). In the second (untrained) person only 200 ml of air will come to alveoles. At respiration freaquency 20 in first person 12000 ml of air reach alveoles for 1 minute (20 x 600 ml). At a freaquency 40 in second person this air amount will be only 8000 ml of air (40 x 200 ml). Thus, in untrained person air amount reaching lungs is lower on 4000 ml. That’s why less respiration freaquency is more physiological! It is reached by training (the best – by physical one). As it is known nowadays, civilized person is healthy, active, energetic and it may be so tens of years if his minute volume is not more than 4-5 l. The more minute volume predominates over this level, the more symptoms are of differnt organs pathologies occur. In people who have such problems (these are the civilization problems!!!) minute volume is equal to 8-12 litres in resting state. One can’t call such respiration healthy. Remember!!! External respiration normalization – reaching minute volume level 3-4 litres per minute! High freaquency of our breathing is delt with its uncorrect character. In the most people amount time for inspiration is approximately equal to time for expiration. Besides, the most people performes their expiration right after their inspiration – it is also out of physiology. It’s necessary to lack someone’s breathing after inspiration and then slower then inspiration expiration comes, after which – new lack. Such respiration type reminds respiration on Buteyko, Frolov et al. But, unfortunately, people become follow this respiration “culture” only when they fell ill. Really it’s necessary to breath in such a way always! This is a Real Way to health and prevention of a great number of diseases!

Lung ventillation. Air-conductive ways, lung parenhyme, pleura, osteo-muscular thorax carcas an dyaphragm are united working organ by which lung ventillation is performed. Lung ventillation – alveolar air gas content renewal process. Such air provides oxygen coming into alveoles and carbon dioxide excessive amount releasing. Ventillation intensivity is determined by respiration depth and freaquency, harmful space. Ventillation occurs due to active physiologic process (respiratory movements). It depends on body stature (vertical or horizontal) and circulation in alveoles.

Gas transition and transfer mechanism. Pressure gradient is vitally essential factor providing gas exchange from one environment to another. What pressure does it mean? Oxygen and carbonic dioxide create definite pressure which is called partial pressure – common pressure part of a given gas in a given mixture. This part depends on gas per cent content in the mixture. The it is more, the partial pressure of given gas is more.

Oxygen transport.

Oxygen partial pressure:

· in atmosphere is equal to 159 mm merc col.;

· in alveoles – 102-105 mm merc col;

· in venous blood reaching alveoles – 40 mm merc col;

· pressure gradient for oxygen between alveoles and blood is about 60 mm merc col.

Thus, oxygen due to this difference of partial pressure and its tension in different environments passes from atmosphere into alveoles and then in blood and tissues. How oxygen is transmitted?

Oxygen transfer conditions

It is known that blood transfers 300-350 ml of oxygen for 1 minute under relative rest state (this ziphra significantly increases at physical work). One can differentiate 2 factors of oxygen transfer:

· large alveolar surface (60-100 square meters);

· oxygen fast diffusion ability – at this difference between alveoles and blood in 1 mm merc col 200 ml of oxygen will diffund; at a real difference that is 60 mm merc col – 12000 ml of oxygen (!even in course of intensive physical loading this ziphra is not more than 4000-5000 ml!). You see data about oxygen diffuse ability: it predominates the level necessary for intensive physical trainings in 2,5-3,0 times.

Oxygen transport forms

Particularly oxygen can be dissolved (in 100 ml of blood – up to 0,3 ml of oxygen, thus, in all blood – about 15 ml). Of course, it can’t solve the problem of oxygen transport. Main chemical substance necessary for oxygen transport is oxyhaemoglobine. It was estimated that 1 g of haemoglobine can transmit approximately 1,31 ml of oxygen. 100 ml of blood contains about 14-16 g of haemoglobine, so, they can carry 18-21 ml of oxygen. This index is known as oxygen blood capacity – is is defined as oxygen amount transporting with 100 ml of blood till its full saturation. This index can change. It is rised up in course of physical training, at polycitaemia; reduced – at blood diseases for instance at anaemias.

Formed oxyhaemoglobine amount depends on oxygen partial pressure in blood. This dependence is linear that is proved by following data. At oxygen partial pressure equal to 0, oxyhaemoglobine isnt’t formed; 10 mm merc col. – 10% oxyhaemoglobine; 20 mm.- 30%; 40 mm. – 70%; 70 mm.- 90%; 100 mm. – 96%. If we connect all this points we shall receive curve describing dependence between oxygen tension in blood and amount of forming oxyhaemoglobine. This curve name is oxyhaemoglobine dissociation curve. One can make some important conclusions from this curve:

1) At oxygen partial tension decreasing in blood up to 80-70 mm merc col (it corresponds to such partial pressure in mountains at a high 2500-3000 meters above sea level) amount of formed oxyhamoglobine decreases insignificantly, i.e. its amount is less only on several per cents than on plain. It gives the possibilities to successful work of mountaineers, highland workers and also to life in highlands without any additional devices and forces. At a high level above 4000 metres we’ll not be able to breath without additional oxygen coming from gas cylinder.

2) Venous blood is rich in oxyhaemoglobine, i.e. it is saturated by oxygen. At partial tension in venous blood equal to 40 mm merc col, up to 70% of oxyhaemoglobine is formed in blood.

3) Difference between oxyhaemoglobine content in arterial and venous blood is 25-26%. Oxyhaemoglobine content in arterial blood is 95-96%, in venous – 70%. This index is named arterio-venous difference. It is rised up in course of physical training, at polycitaemia; reduced – at blood (at anaemias) and heart disorders.

Oxyhaemoglobine dissociation curve moving:

1) to the left (up) – is observed:

· at temperature decreasing;

· pH increasing (alkalosis);

· hypocapnia;

· in blood reaching lungs;

· in new-borns;

· in mountaineers;

· in fliers;

· in cosmonauts.

Essence: at less oxygen partial pressure in atmosphere to form more oxyhaemoglobine in blood.

2) To the right (down) – is observed:

· at hyperthermia;

· at fever;

· pH decreasing (acidosis);

· carbonic acid content increasing;

· in blood reaching tissues (for example, working muscles).

Essence: at the same oxygen partial tension oxygen forming is less and free oxygen comes to the tissue where it’s necessary for redox reactions performing in them.

Carbon dioxide transport

Carbon dioxide transmission and transfer is realized by same mechanisms. Carbon dioxide tension:

· in tissues – maximal – 60 mm merc col.;

· in venous blood outflowing from tissues – 46 mm;

· in alveoles where venous blood inflows – 38 mm merc col;

· in atmosphere – 0,2 mm merc col.

It’s quite naturally that pressure and tension gradient in different organism environments and compartments provides carbonic dioxide transition from tissues to blood, from blood into alveoles and from alveoles into surrounding space.

Carbon dioxide forms

Particularly, like oxygen, in little amounts it can dissolves (3-6%). Rest part comes into chemical connections both in plasma and in erythrocytes. Chemical substance of carbonic dioxide with water – carbonic acid (H₂CO₃) – appears in plasma. It takes place because partial tension of this gas is more than in blood, that’s why it transfers into blood plasma where is connected to water. Carbonic acid part in plasma is connected to sodium chloride as the result of which soda is formed (NaHCO₃). Plasma transports carbonic dioxide in composition of these compounds. Its rest part reaches erythrocytes where under influence of special erythrocytic enzyme carboanhydrase the possibility of its connection with water is significantly increased with carbonic acid forming. Little amount of this acid is binded with potassium chloride with potassium bicarbonic (KHCO₃) formation. Finally, carbon dioxide part is binded to amine group of haemoglobine with the carbohaemoglobine (KHCO₂)forming. Thus, in erythrocytes carbonic dioxide is transported in a structure of H₂CO₃, KHCO₃ and HbCO₂.

When blood reaches alveoles, same enzyme carboanhydrase acts on the contrary: it helps H₂CO₃ dissociation and CO₂ comes into alveoles as the result of these processes. As oxygen partial pressure in alveoles is higher than in blood the gas passes in blood, in red blood cells with oxyhaemoglobine forming in them. Being more powerful acid than carbonic, ohyhaemoglobine takes the bases from bicarbonates and thus provides carbonic dioxide releasing. The result: CO₂ passes into alveoles. In tissues oxyhaemoglobine transformes into haemoglobine giving bases connected with it, increasing blood saturation with CO₂. These examples testify to the fact that oxygen plays essential role in CO₂ forming and releasing.

But at all these reactions CO₂ tension in venous blood remains big (46 mm merc col) and it doesn’t differ significantly from its tension in arterial blood. Thus, there exists carbonic dioxide arterio-venous difference equal to 6 mm merc col.

There is quite natural question: why organism has big amount of CO₂? The answer is the following: it is essential respiration regulator.

 

Lecture 20.

Respiration regulation.

Respiration regulation is performed by means of reflectory reactions occuring as a result of excitement of specific receptors located in lung tissue, vascular reflexogenic zones and other regions. Respiration regulation central apparatus are the structures of:

· spine;

· medulla oblongata;

· hypothalamus;

· brain hemispheres.

Main function of respiration management is performed by stem repiratory neurons which transmit rhythmic sygnals into spine to respiratory muscles motoneurons.

Respiratory nervous center – is central nervous system neurons integrity providing respiratory muscles co-ordinated rhythmical activity and external respiration constant adaptation to changing conditions inside organism and in environment. Main (working) part of respiratory nervous center is located in medulla oblongata. One can differentiate 2 parts in it: inspiratory (inspiration center) and expiratory (expiration center). Medulla oblongata respiratory neurons dorsal group primarily consists of inspiratory neurons. They give particularly the stream of descendant ways getting the contact with diaphragmal nerve motoneurons. Respiratory neurons ventral group sends primarily descendant fibres to intercostal muscles motoneurons. One can see region in pons anterior part called as pneumotaxic center. This center deals with activity both of inspiratory and expiratory center parts providing the change of inspiration and expiration. Respiratory center important part is neurons group of spine cervical part (III-IV cervical segments), where diaphragmal nerves nuclei are situated.

Respiratory center excitement mechanisms are the following.

· One of the most important ways of its excitement is automatism. There is not one point of view to automatism nature but there exist data about secondary depolarization occurence in respiratory neurons (like diastolic depolarization in myocardium) which reaching its critical level gives new impuls.

· But one of main ways of respiratory center excitement is its irritation by carbonic acid. As it was mentionned above, there remains much carbonic acid in blood leaving lungs. It performs the function of medulla oblongata neurons main irritator. It is mediated through special structures – chemoreceptors, located directly in medulla oblongata structures (“ central chemoreceptors ”). Thus, the second way – through blood.

· They are very sensitive to carbonic dioxide tension and acid-alkaline state of intercellular liquor washing them.

· Carbonic acid can easily diffund from brain vessels in liquor and stimulates medulla oblongata chemoreceptors.

· Reflectory way - there are 2 reflexes groups (like for cardio-vascular system): proper and conjugated.

I. Proper reflexes – the reflexes originated from respiratory system organs and finished in it.

1) Reflex from lung mechanoreceptors. According to localization and type of percepted irritations, reflectory answer to irritation one can differentiate 3 types of such receptors: receptors of stretching, irritant receptors and lung juxtacapillary receptors.

· Lung stretching receptors – are primarily located in air ways (trachea, bronchi) smooth muscles. There are approximately 1000 receptors in every lung and they are connected with respiratory center by large mielinized afferent fibres of vagus with very high conductance velocity. Direct irritator – internal tension in air ways walls tissues. Such impulses freaquency is increased at lung stretching in course of inspiration. Lung swelling causes inspiration reflectory inhibition and transition to expiration. These reactions are stopped at vagus cutting and respiration becomes retarded and deep. Mentionned reactions are called Gering-Breyer’s reflex. This reflex is reproduced in adult person when his respiratory volume is more than 1 l (at physical training for instance). It is of essential importance in new-borns. Their adaptation is slow.

· Irritant receptors or slowly adaptating air ways mechanoreceptors, trachea and bronchi mucosa receptors. They answer to lung volume significant changes, chemical or mechanical irritators (mucus, tobacco, dust particles and so on) action to mucosa. Their adaptation is fast. At side bodies coming into respiratory ways there occurs cough reflex after irritant receptors activation. Reflectory arch of cough reflex – receptors – superio-laryngeal, glosso-pharyngeal, trygeminal nerves – expiratory part of respiratory center. Result - strong expiration – cough. At isolated irritation of nasal respiratory ways receptors second immediate expiration occurs – sneezing.

· Juxtacapillary receptors are located near alveolar and respiratory bronchi capillaries. Irritators: pressure increasing in circulation small circle and intersticial liquid volume increasing in lungs. Such situation is observed at blood stagnation in small circulation circle, lung oedema, lung tissue injury (at pneumonia et al.). Impulses from these receptors are directed to respiratory center through vagus causing freaquent surface breathing occurence. There may be not only freaquent breathing (tachypnoe) but also reflectory bronchoconstriction.

2) Reflexes from respiratory musculature proprioreceptors:

· Reflex from intercostal muscles proprioreceptors is realized in course of inspiration when these muscles while their contraction send information through intercostal nerves to respiratory center expiratory part and as a result expiration occurs.

· Reflex from diaphragm proprioreceptors – is performed as an answer to its contraction in course of inspiration. Result: information comes through diaphragmal nerves first in spine, than in medulla oblongata in its expiratory part and expiration occurs.

Thus, all respiratory system proper (own) reflexes are realized in course of inspiration and are resulted in expiration.

II. Conjugated reflexes – reflexes originated out of respiratory system.

1) Reflex onto conjugation of blood circulation and respiration systems – is originated from perypheral chemoreceptors of vascular reflexogenic zones. The most sensitive of them are located in sino-carotid zone region.

· Sino-carotid chemoreceptive conjugated reflex – is performed at carbonic dioxide accumulation in blood. If its tension increases than the irritation of the most sensitive chemoreceptors (they are in this zone in sino-carotid body) occurs, excitement wave comes from them through IX pair of cranio-cerebral nerves and reaches respiratory center expiratory part. Expiration occurs which enforces releasing of excessive carbonic acid in surrounding space. Thus, blood circulation system (while this reflectory act perfomance it works more intensively: heart contractioin freaquency and blood stream velocity increase) influences on respiration system.

2) Exteroreceptive reflexes are originated from tactile (remember your breathing reaction on touching of lovely person), temperature (warmth – increases, coldness – decreases respiratory function), noceoceptive (weak stimuli and of a middle force - increase, strong – suppress breathing) receptors.

2) Proprioreceptive reflexes – are performed due to irritation of receptors of sceletal muscles, joints, ligaments. It is observed in course of physical training doing. Why? If under rest state it’s necessary 200-300 ml oxygen per minute for human than at physical loading given volume must be significantly increased. Under these conditions both minute volume and arterio-venous difference on oxygen are increased. These indexes increasing is accompanied by oxygen consumption rising up. At work duration of only 2-3 minutes and its significant power oxygen consumption grows uninterruptedly from the very beginning of work and is decreased only after its stoppage. At work duration more, oxygen consumption, while increasung in course of first minutes, is supported all the time on its constant level. Oxygen consumption increases the more the harder physical work it is. Maximal oxygen amount that organism can use per 1 minute at the hardest work for it is called oxygen maximal consumption (OMC). Work at which person reaches his OMC level must have duration not less then 3 minutes. There exists many ways of OMC determining. It doesn’t predominate 2,0-2,5 l/min in untrained people. It can be twice large in sportsmen and even more. OMC is an index of organism aerobic productivity. This human ability to perform very hard physical work, providing his energetic consumption due to oxygen used directly in course of work. It is known that even well-trained person can work at oxygen consumption 90-95% from his OMC level not more than 10-15 min. One having more aerobic productivity reaches better results in work (sport) at practically equal technic adn tactic preparation. Why oxygen consumption is increased in course of physical activity? One can differentiate several reasons:

· additional capillaries opening and blood increasing in them;

· oxyhaemoglobine dissotiation curve movement to the right and below;

· temperature increasing in muscles.

For performing their work, muscles need in energy, the accumulations of which are restored while oxygen transport. Thus, there exists definite dependence between work power and oxygen amount necessary for work. That blood amount necessary for work is called oxygen asking. Oxygen asking can reach up to 15-20 liters per minute and even more in course of hard work. But maximum of oxygen consumption is less in 2-3 times. Does it possible to perform the work if minute oxygen accumulation predominates OMC? For correct answer this question one should remember for what oxygen is used in course of muscular activity. It is essential for macroergic substances restoration providing muscular contraction. Usually oxygen interacts with glucose and it releases the energy while its oxidation. But also glucose can be destructed without oxygen, i.e. by abaerobic way as a result of which energy releases too. These are also other substances possessing the ability to be destructed without oxygen. Thus, muscular activity can be provided at insufficient oxygen coming into organism too. But in this case many acid products are formed and it’s necessary oxygen for their destruction because they are destructed by oxidation. Oxygen amount necessary for metabolism products oxidation that were formed in course of physical activity is called oxygen debt. It appearsin course of work and is liquidated in restoration period after work end. Usually this disappearing takes from several minutes to 1 hour and a half. Everything depends on work duration and intensivity. Lactic acid plays the most important role in oxygen debt forming. To continue his work at lactate presence in blood in great amounts organism must have powerful buffer systems and his tissues are to be adapted to work under hypoxy conditions. Such organism adaptation serves as one of factors providing high aerobic productivity. All the mentionned above complicate respiration regulation at physical activity because oxygen taking in organism is increased and its blood hypoxy leads to chemoreceptors irritation. Sygnals from them come in respiratory center as the result of which respiration becomes more freaquent. A great number of carbonic acid is formed in course of muscular activity that comes into blood and it can acts to respiratory center directly through central chemoreceptors. If blood hypoxy leads primarily to breathing quickening than carbonic acid surplus causes its deepening. Both these factors act simultaneousely in course of physical activity and that’s why respiration quickening and deepening takes place. Finally, impulses coming from working muscles, reach respiratory center and enforces its activity. At respiratory center functionning all its parts are functionally interconnected by means of following mechanism: at carbonic acid accumulation respiratory center inspiratory part is excited from information comes in pneumotaxic part, then to its expiratory part. The latest, besides, is excited by means of a whole group of reflectory acts – from receptors of lungs, diaphragm, intercostal muscles, respiratory ways, vessels chemoreceptors. Inspiration center activity is inhibited due to its excitement through special inhibitory reticular neuron and inspiration is changed by expiration. As expiration center is inhibited it doesn’t send impulses far into pneumotaxic center and information flow is stopped from it to expiration center. Carbonic acid is accumulated in blood by this time and inhibitory influencings on expiratory part are inhibited. Inspiration center is excited due to such information flow redisposition and expiration is changed by inspiration. And everything is repeated again.

Vagus is an essential link in respiration regulation. Main influencings to expiration center come through it. That’s why at its injury (like at pneumotaxic center injury) respiration is changed so that inspiration remains normal and expiration is sharply prolonged – vagus-dyspnoe.

As it was mentionned above in course of coming to the highlands lung ventillation increasing occurs based on vascular zones chemoreceptors stimulation.

Heart contraction freaquency and minute volume are increased simultaneously with this. These reactions improve oxygen transport in organism a little but not not for long. That’s why at durable staying into mountains with adaptation to chronic hypoxy initial (urgent) respiration reactions gradually leave their place to more economic adaptation of gas-transport organism system. In constant residents of highlands respiration reaction to hypoxy is too weak (hypoxic deafness) and lung ventillation is supported practically on the same level like in plane residents. At the same time at durable staying under conditions of highlands vital lung capacity, caloric oxygen equivalent, myoglobine content in muscles, mitochondrial enzymes activity (providing biological oxidation and glycolysis) are increased; organism tissues (particularly central nervous system) sensitivity to insufficient oxygen supply is decreased. At high more than 12000 m air pressure is very small and under these conditions even breathing by pure oxygen doesn’t solve the problem. That’s why at flyings at this high one need hermetic cockpits (planes, cosmic ship).

Sometimes human being has to work under increasing pressure conditions (divering). In the depth nitrogen becomes its dissolving in blood and in course of fast rising out off the depth it doesn’t manage to release from blood, gas vesicles cause vessel emboly. Occuring condition is called kessonic disease. It is accompanied by pain in joints, giddiness, dyspnoe, unconsciousness. That’s why nitrogen in air mixtures is changed on insoluble gases (for instance, helium).

Human being can delay free his breath not more than on 1-2 minutes. After preliminary lung hyperventillation this respiration delay is rised up to 3-4 minutes. But durable, for example, diving after hyperventillation is very dangerous. Blood oxygenation sharp decreasing can cause sudden unconsciousness. Under this state swimmer (even experienced one) under stimulus action caused by carbonic acid partial tension increasing in blood can inspirate water and choke (drown).

Thus, at the end of our lecture we must to remember you that healthy breathing – is nasal, as slow and seldom as possible, with its lack in course of inspiration and, especially, after it. While prolonging the inspiration, we stimulate vegetative nervous system sympathetic part work with all following consequences. While prolonging the expiration, we carry carbonic acid in blood more and longer that positively influences on blood vessels tone (decreases it) will all following consequences. Due to this oxygen under such situation can come in the farthest microcirculative vessels preventing disorders of their function and development of many diseases. Correct breathing – is a prevention and treatment of big group of diseases not only of respiratory system but also of other organs and tissues! Breath for enjoy!

 

 

Lecture 21.