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BIO169-Respiratory
Respiratory System
| Question | Answer |
|---|---|
| what is atmospheric pressure? | aka barometric; 760 mmHg at sea level |
| what is intrapulmonic pressure? | pressure inside the alveoli (aka intraalveolar); varies with respiratory cycle |
| what is intrapleural pressure? | pressure in the pleural cavity which contains the lung; it also varies with the respiratory cycle, but it is always subatmospheric |
| how is air moved in and out of the lungs? | the interaction of atmospheric, intrapulmonic, and intrapleural pressures |
| what is inspiration? | movement of air into the lungs |
| how does inspiration work? | contraction of the diaphragm and external intercostals will increase the volume of the thoracic cavity |
| what happens to intrapleural pressure during inspiration? | an increase in volume of a closed container will cause a decrease in pressure within that container; accordingly intrapleural pressure will drop |
| what happens to intrapulmonic pressure during inspiration? | because the moist surfaces of the pleural membranes adhere to each other (i.e. surface stension between parietal pleura and visceral pleura), the lungs expand and intrapulmonic pressure will also decrease and become subatmospheric |
| how does air move during inspiration? | air will rush into the lungs, down the pressure gradient which now exists between the lungs and the atmosphere |
| where does gas exchange take place? | across the alveoli |
| what would be typical intrapleural and intrapulmonic pressures at rest? | 760 mmHg intrapulmonic; 756 mmHg intrapleural; 4 mmHg transpulmonary pressure |
| what would be typical intrapleural and intrapulmonic pressures during inspiration? | 757 mmHg intrapulmonic (3 mmHg less than atmospheric pressure); 754 mmHg intrapleural (6 mmHg less than atmospheric pressure) |
| what is expiration? | movement of air out of the lungs |
| how does expiration work? | relaxation of the diaphragm and external intercostals results in a decrease in lung volume |
| what happens to intrapulmonic pressure during expiration? | decrease in lung volume causes increase in pressure within the lungs; in addition, the elastic recoil properties of the lungs themselves will further increase the pressure in the lungs |
| how does air move during expiration? | air moves out of the lung down the pressure gradient that exists between the lungs and the atmosphere |
| which is more passive - inspiration or expiration? | normal expiration is considered to be more passive, because muscle relaxation and elastic recoil reduces intrapulmonic volume and increases intrapulmonic pressure |
| what is forced expiration? | additional air can be forced from the lungs by contraction of the internal intercostals and the abdominal muscles; contraction of these further compresses the lung volume and elevates the intrapulmonic pressure |
| what is surfactant? | a soapy-like fluid which is produced by the epithelial cells of the alveoli |
| what is the function of surfactant? | it decreases surface tension in the alveoli and prevents the collapse of small alveoli; it is important in maximizing the available surface area of respiratory membrane for gas exchange |
| when does surfactant begin to be produced in fetal development? | not until the end of normal gestation because the lungs are not used in utero; many premature infants have trouble keeping their lungs expanded and have difficulty breathing |
| what is compliance? | a characteristic change in volume which is produced by a change in pressure |
| how can blowing up balloons be used to illustrate compliance? | it is easier to blow up a round balloon than a long, skinny one with the same amount of effort; this is because the round balloon has a greater compliance that the long skinny one |
| what causes the compliance of the lungs? | the elasticity of the lung tissue and thoracic cage, and the surface tension in the alveoli |
| what is indicated by a high compliance? | when the lungs have high elasticity and low surface tension, which makes the healthy lungs easy to expand |
| when does compliance decrease? | when there is a increase in lung stiffness as in fibrotic lung diseases, when the small airways are blocked by secretions as in pneumonia, or when surfactant production decreases; also, if there is a change in structure of thoracic cage, (osteoporosis) |
| what is an example of a fibrotic lung disease? | tuberculosis |
| when happens to a lung with increased compliance? | it is hard to inflate, so inspiration becomes difficult |
| when does compliance increase? | when there is a decrease in elastic recoil properties of the lung tissue, making the lung become "floppy" and too distensible |
| what happens when compliance increases? | the lung becomes "floppy" and too distensible; it causes difficult expiration, as it is hard to squeeze air out |
| what is one cause of increased compliance? | emphysema (COPD) causes a breakdown in the elastic connective tissue of the lung causing an increase in compliance |
| how is pulmonary ventilation regulated? | by CNS respiratory centers and chemoreceptors |
| what are the 2 CNS respiratory control areas in the brain? | in the medulla - regulates rhythm (rate & depth) of breathing; in the pons - regulates the transition between inspiration and expiration and keeps it smooth |
| what are the 2 medullary centers? | the dorsal respiratory group (DRG) and the ventral respiratory group (VRG) |
| what do the neurons of the DRG control? | the pace for the respiratory center as a whole; it is often called the inspiratory center |
| how does the DRG control inspiration? | action potentials from the DRG travel in the phrenic and intercostal nerves to cause contraction of these muscles so that inspiration can occur; the DRG then becomes dormant and expiration occus by passive means |
| what is the function of the VRG? | the VRG is composed of neurons with a less understood function; it is believed the VRG neurons function during forced expiration or whenever extra effort to breathe is required |
| what are the 2 respiratory centers in the pons? | the pneumotaxic center and the apneustic center |
| what is the function of the pneumotaxic center? | this center functions primarily to inhibit the medullary areas |
| what is the function of the apneustic center? | the existence of this center is hypothetical (it has never been identified); it is hypothesized to consistently drive the inspiratory center in the medulla |
| what are the 2 types of chemoreceptors which regulate pulmonary ventilation? | the central chemoreceptors are located in the medulla and the peripheral chemoreceptors are located in the aortic and carotid bodies |
| what do the central receptors detect? | they are most sensitive to levels of CO2 (PCO2) in the bloodstream and also to pH; they are by far the most important in producing respiratory drive |
| what is the normal range of PCO2? What is the normal pH range of blood? | PCO2 normal range is 35-45 mmHg; normal pH range of blood is 7.35 - 7.45 |
| what stimulates the central chemoreceptors? | increased CO2 levels and decreased pH |
| what occurs when the central cehemoreceptors are stimulated? | increase in respiratory rate |
| what do the peripheral chemoreceptors detect? | decreased PO2 (but only if it drops below 60 mmHg); the peripheral chemoreceptors are relatively insensitive to CO2 |
| what is the normal range for PO2? | 80-100 mmHg |
| what is the Hering-Breuer Inflation reflex? | this reflex guards against overinflation of the lung, which might damaged the tissues |
| how is the Hering-Breuer inflation reflex stimulated? | there are stretch receptors in the interstitial tissues of the lungs, which when stimulated will trigger a forced expiration |
| what are pulmonary irritant reflexes? | these are stimulated by irritating stimuli, primarily in the airways; they result in the production of coughing to clear the airways |
Created by:
debmurph
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