Respiration Flashcards
Describe the effect of the autonomic nervous system on the bronchioles
- symp. activates beta-2 adrenergic receptors, leading to relaxation and dilation of the airways
- parasymp. activates muscarinic receptors, leading to contraction and constriction of the airways
What is atmospheric pressure?
- pressure exerted by the weight of the gas int he atmosphere on objects on the surface of earth
- 760 mmHg at sea level
- set to 0 for relative pressure
What is intra-alveolar pressure?
- intra-pulmonary pressure
- pressure within the alveoli that increases and decreaes with each breath
- always equal to atmospheric pressure at the end of inspiration and expiration
What is intra-pleural pressure?
- pressure within the pleural cavity, exerted outside the lungs
- usually -4 mmHg
What is transpulmonary pressure?
- pressure gradient that holds the lungs open
- pressure difference between intra-alveolar and intra-pleural pressures
What is transthoracic pressure?
- prevents the thoracic wall from moving outwards
- pressure difference between intra-pleural and atmospheric
What does pulmonary surfactant do, and what produces it?
- produced by type 2 alveolar cells
- disperses between water molecules and decreases attraction between them
- decreases surface tension
- enhances lung compliance
What is alveolar ventilation, and how do you calculate it?
total rate of air movement into and out of lungs, correcting for dead space
(tidal volume - dead space volume) X respiratory rate
What is P50?
the partial pressure at which hemoglobin is 50% saturated
What is the effect of increased CO2 on the O2-Hb Dissociation Curve?
increase in metabolic activity: more CO2 and H+
- more O2 unloaded to tissues, so decreased Hb affinity for O2
- increased P50
- right shift of curve
What is the effect of increased temperature on the O2-Hb Dissociation Curve?
increase metabolic activity: heat production
- more O2 unloaded to tissues, so decreased Hb affinity for O2
- increased P50
- right shift of curve
What is the effect of 2,3-DPG on the O2-Hb Dissociation Curve?
- by product of glycolysis in RBCs
- binds reversibly to Hb, so reduces affinity for O2
- P50 increases
- right shift of curve
Describe what happens to CO2 in the blood, and the Chloride shift
- CO2 enters RBC and is converted to bicarbonate ion by carbonic anhydrase
- bicarbonate ion exits RBC by passive diffusion
- H+ stays in cell and binds to Hb
- RBC now has pos net charge, so Cl- ions from NaCl in blood enter cell
- the Na+ binds to the bicarbonate ions in plasma
- increased ability of plasma to carry CO2
What is the Bohr effect?
- an increase in CO2 leads to an increase in H+, which leads to a right shift in the curve
- this leads to Hb unloading O2 more readily: decrease in Hb affinity for O2 due to decreased pH
What is the Haldane effect?
an increase in O2 released from Hb leads to an increase in the CO2 and H+ uptake by Hb
What is the effect of CO on the O2-Hb Dissociation Curve?
- decreases O2 binding capacity: CO binds with higher affinity to Hb, takes up 2 binding sites
- causes left shift of curve
- increases Hb affinity for O2 on the 2 empty spots
- decreased P50
What factors affect diffusion across the respiratory membrane?
Will an increase or decrease cause and increase in diffusion?
- thickness of membrane (decrease)
- surface area of membrane (increase)
- diffusion coefficient (increase)
- partial pressure gradients (increase)
What is the partial pressure of O2 and CO2 in the lungs, in the arteries, and in the veins?
alveoli: PO2 100, PCO2 40
arteries: PO2 100, PCO2 40
veins: PO2 40, PCO2 46
Where are Peripheral Chemoreceptors located, and what do they do?
- in carotid and aortic bodies
- sense decrease in arterial PO2 below 60 mmHg
- sends impulses to medulla, which increases ventilation
Where are Central Chemoreceptors located and what do they do?
- in medulla
- control minute-to-minute breathing
- sense changes in pH of ECF in brain, due to changes in PCO2
- send impulse to increase ventilation
Describe the effect of increased H+, not related to increase PCO2
- peripheral chemoreceptors sense increased arterial H+, and send impulses to medulla
- this increases ventilation and decreases arterial PCO2 and H+
What is the Hering-Breur Relfex?
- limits the degree to which inspiration proceeds, and prevents overinflation of the lungs
- stretch receptors in walls of bronchi and bronchioles initiate action potentials that stimulate expiration
What are the acclimatizations to high altitude?
- hyperventilation
- polycythemia
- pulmonary vasoconstriction
- increased production of 2,3-DPG
- increased capillary density in tissues
- increase mitochondria density
- increased muscle myoglobin content
