Chemical Control of Breathing

Question 1

What do FETCO₂ and FETO₂ measure?

Answer 1

Fraction of CO₂ and O₂ at the end of a tidal breath

Question 2

What do PETCO₂ and PETO₂ measure?

Answer 2

Pressure of CO₂ and O₂ at the end of a tidal breath

Question 3

Why do PETCO₂ and PETO₂ increase when breathing a CO₂ enriched mixture?

Answer 3

CO₂ increases because of the hypercapnic gas mixture

O₂ increases due to compensational hyperventilation

Question 4

Why does ventilation increase during CO₂ breathing?

Answer 4

High levels of CO2 increases activation of the chemoreceptors which cause an increase in the volume of gas inhaled/exhaled from the lungs (V_E)

Question 5

What happens to a subjects H⁺ levels during CO₂ breathing?

Why?

Answer 5

H+ levels increase due to respiratory acidosis - associated with CO₂/H⁺ buffer

Question 6

WHat are the effects of breathing and plasma [H⁺] of chronic alveolar hypoventilation?

Answer 6

Loss of sensitivity to CO₂ with chronic exposure

Question 7

Why do PETCO₂ and PETO₂ decrease when breathing a hypoxic gas mixture?

Answer 7

O₂ decreases because of the hypoxic (low oxygen) mixture

CO₂ decreases because of hyperventilation

Question 8

Why is there a difference in ventilation (V_E) between breathing a CO₂ enriched mixture and breathing a hypoxic mixture?

Answer 8

Breathing increases more with hypercapnia than with hypoxia because within physiologic range the oxygen receptors are not very sensitive (when oxygen is >60mmHg). On the other hand, CO₂ receptors are highly sensitive so with small increase in CO₂ there is a larger change in ventilation

Question 9

How would you characterize a subjects H⁺ status during hypoxia?

Answer 9

Hypoxia causes an increase in ventilation which decreases CO₂ levels and can cause respiratory alkalosis

Question 10

How do those born in high altitiude adapt to the decreased oxygen levels?

Answer 10

They develop increased surface area for gas exhange in their lungs

Question 11

The carotid body is innervated by sensory fibers originating in the ______ _______, traveling through the carotid sinus nerve to the _______ ______ _______

Answer 11

Petrosal ganglion; nucleus tractus solitarius

Question 12

The origin and transduction of the chemoreceptor signal is likely to involve changes in…(2)

Answer 12

• Conductance of potassium channels
• Intracellular calcium

Question 13

What are the sites of respiratory chemoreceptors?

Answer 13

• Pre-Botzinger complex
• Retrotrapezoidal nucleus
• Lateral parapyramidal area
• Nucleus tractus solitarius

Question 14

Is the ventilatory response greater to respiratory acidosis or metabolic acidosis?

Answer 14

Respiratory acidosis