Respiration

Question 1

Describe the effect of the autonomic nervous system on the bronchioles

Answer 1

• 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

Question 2

What is atmospheric pressure?

Answer 2

• 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

Question 3

What is intra-alveolar pressure?

Answer 3

• 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

Question 4

What is intra-pleural pressure?

Answer 4

• pressure within the pleural cavity, exerted outside the lungs
• usually -4 mmHg

Question 5

What is transpulmonary pressure?

Answer 5

• pressure gradient that holds the lungs open

- pressure difference between intra-alveolar and intra-pleural pressures

Question 6

What is transthoracic pressure?

Answer 6

• prevents the thoracic wall from moving outwards

- pressure difference between intra-pleural and atmospheric

Question 7

What does pulmonary surfactant do, and what produces it?

Answer 7

• produced by type 2 alveolar cells
• disperses between water molecules and decreases attraction between them
• decreases surface tension
• enhances lung compliance

Question 8

What is alveolar ventilation, and how do you calculate it?

Answer 8

total rate of air movement into and out of lungs, correcting for dead space

(tidal volume - dead space volume) X respiratory rate

Question 9

What is P50?

Answer 9

the partial pressure at which hemoglobin is 50% saturated

Question 10

What is the effect of increased CO2 on the O2-Hb Dissociation Curve?

Answer 10

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

Question 11

What is the effect of increased temperature on the O2-Hb Dissociation Curve?

Answer 11

increase metabolic activity: heat production

• more O2 unloaded to tissues, so decreased Hb affinity for O2
• increased P50
• right shift of curve

Question 12

What is the effect of 2,3-DPG on the O2-Hb Dissociation Curve?

Answer 12

• by product of glycolysis in RBCs
• binds reversibly to Hb, so reduces affinity for O2
• P50 increases
• right shift of curve

Question 13

Describe what happens to CO2 in the blood, and the Chloride shift

Answer 13

• 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

Question 14

What is the Bohr effect?

Answer 14

• 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

Question 15

What is the Haldane effect?

Answer 15

an increase in O2 released from Hb leads to an increase in the CO2 and H+ uptake by Hb

Question 16

What is the effect of CO on the O2-Hb Dissociation Curve?

Answer 16

• 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

Question 17

What factors affect diffusion across the respiratory membrane?
Will an increase or decrease cause and increase in diffusion?

Answer 17

• thickness of membrane (decrease)
• surface area of membrane (increase)
• diffusion coefficient (increase)
• partial pressure gradients (increase)

Question 18

What is the partial pressure of O2 and CO2 in the lungs, in the arteries, and in the veins?

Answer 18

alveoli: PO2 100, PCO2 40
arteries: PO2 100, PCO2 40
veins: PO2 40, PCO2 46

Question 19

Where are Peripheral Chemoreceptors located, and what do they do?

Answer 19

• in carotid and aortic bodies
• sense decrease in arterial PO2 below 60 mmHg
• sends impulses to medulla, which increases ventilation

Question 20

Where are Central Chemoreceptors located and what do they do?

Answer 20

• 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

Question 21

Describe the effect of increased H+, not related to increase PCO2

Answer 21

• peripheral chemoreceptors sense increased arterial H+, and send impulses to medulla
• this increases ventilation and decreases arterial PCO2 and H+

Question 22

What is the Hering-Breur Relfex?

Answer 22

• 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

Question 23

What are the acclimatizations to high altitude?

Answer 23

• hyperventilation
• polycythemia
• pulmonary vasoconstriction
• increased production of 2,3-DPG
• increased capillary density in tissues
• increase mitochondria density
• increased muscle myoglobin content