Respiratory Physiology Flashcards
(34 cards)
How does parasympathetic system innervate the respiratory structure?
Cholinergic neurons activate muscarinic receptors, leading to constriction of bronchial smooth muscle.
How does Sympathetic system innervate the respiratory structure?
Adrenergic neurons activate beta2 receptors, leading to dilation of bronchial smooth muscle.
What happens to intrapleural cavity in case of pneumothorax?
Usually negative intrapleural pressure goes to atmospheric pressure, zero, and the lungs will try to collapse, while chest wall will try to spring out.
Explain the effect of emphysema on Functional Residual Capacity (FRC).
With elastic fibers in the alveoli destroyed, it is harder to press on alveoli with collapsing pressure, and the at the original FRC the airway pressure overall is negative. More volume need to be flood in, and this increases FRC.
Explain the effect of Chronic Pulmonary Obstructive Disease (COPD) on the forced expiration.
Intrapleural pressure will be raised upon forced expiration like a normal person, but loss of elasticity will decrease transmural pressure and therefore alveolar pressure and airway pressure in the respiratory structure, given fixed intrapleural pressure. This decreases the intrathoracic pressure to negative values at the top of airway and collapses. Hard to breathe out air out of the chest. For treatment, patient learns to expire with pursed lips.
What causes hysteresis? Between inspiration compliance curve and expiration compliance curve?
Because intermolecular force between liquid-air (surface tension) is stronger during initial stage of inspiration, I.e. Flatter compliance portion, whereas that is lower during initial stage of expiration and intermolecular bondings break up more easily at large lung volume and density of surfactant is higher, I.e. Flatter compliance.
Describe three ways airway resistance can increase.
More viscous air flowing in.
Longer conducting respiratory passageway.
Shorter radius of passageway (vasoconstriction of SM)–so parasympathetic autonomic nervous system.
Describe three ways collapsing pressure in alveolus can increase.
Small alveolus volume.
Higher transmural pressure across alveolus (more elastance)
Less surfactant on the surface.
Describe the effects of asthma on Vt, RV, FRC, and airway resistance.
To trade off the increased work caused by viscosity, Vt will actually increase. Airway resistance will increase. Because now it’s harder to get out air during expiration RV is gone higher, and probably FRC (decrease in elastic recoil).
Describe the effects of Polio on Vt, RV, FRC.
Effort dependent work is all affected negatively. Vt and TLC decreased, RV actually increased. Elastic work by alveoli, partially indicated by FRC, might be actually fine (FRC is unchanged) if pulmonary mechanics have remained okay.
Describe the effects of Obesity on Vt, RV, FRC.
The effective decrease in compliance in chest wall with the increased chest and abdominal weight reduces Vt, FRC, and TLC.
Why is PO2 in arterial blood slightly lower than that in alevoli?
Because there is physiologic shunt, in which system blood does not go to pulmonary circulation.
Describe what causes shift to the right in the hemoglobin-O2 dissociation curve.
Decrease in pH Higher PCO2 Increased temperature High O2 metabolism in the tissues Increased 2,3 DPG concentration.
Describe what causes shift to the left in the hemoglobin-O2 dissociation curve.
Increase in pH
Lower PCO2
Decreased temperature
Decreased 2,3 DPG concentration.
Fetal hemoglobin (binds 2,3 DPG less efficiently)
CO competitive binding (total O2 saturation goes low as well)
Why is it advantageous to have HCO3- as a buffer in RBC in the venous end of capillaries?
Because resulting H+ is a better buffer for deoxygenated hemoglobin than oxygenated one.
Explain the effect of Chronic Pulmonary Obstructive Disease (COPD) on inspiration.
Intrapleural pressure goes higher than normal, because loss of elasticity decreases transmural pulmonary pressure at FRC+Vt, given fixed alveolar pressure. This decreases venous return and cardiac output.
What four compensatory changes when venous PO2 gets too low?
Flow (Q or CO) increases
Inter capillary distance decreases
Arterial PO2 increases
Oxygen consumption rate in tissue decreases
What are four assumptions made in the Krogh cylinder model of tissue oxygen uptake?
- All regions of the tissue cylinder consume O2 at the same rate.
- The rate of O2 consumption is not influenced by the local PO2.
- All tissue capillaries are arranged in a parallel array (not tenable)
- There is no longitudinal diffusion of O2 within the cylinder.
When does the alveolar pressure equates to atmospheric pressure AND pleural pressure most negative?
End of inspiration when there is no flow. Lung recoil pressure is highest.
When does the alveolar pressure reach the highest positive value in the respiratory cycle?
When expiration flow is the biggest, I.e. Driving pressure out to mouth is highest.
What happens to elastic energy during expiration to FRC?
It is recovered from the elastic structures of the respiratory system. Even when expiratory muscles are activated.
What is typical lung recoil pressure at FRC?
5cmH2O
At what chest recoil pressure and intrapleural pressure is the lung volume at or close to TLC?
Chest recoil pressure (transthoracic pressure) is positive value, meaning inward recoil, and intrapleural pressure is positive value too.
Describe relationship between effect of surfactant and alveolar surface area in terms of lung recoil pressure.
Lung recoil pressure is greater as surface area increases. Don’t think about lung volume.
