Lab 6 Discussion Questions

Question 1

Relative to normal breathing, how did rebreathing affect the duration of the breath hold? Amount of CO2 before and after the breath hold? Explain.

Answer 1

• Before hold: more CO2 b/c breathing same air and not getting rid of CO2
• Breath hold was shorter than normal b/c chemoreceptors sensed high [CO2] sooner

Question 2

Relative to normal breathing, how did hyperventilation affect the duration of the breath hold? Amount of CO2 before the breath hold? Explain.

Answer 2

• Before hold: less CO2 b/c exhaling more CO2 than body is producing
• Breath hold was longer than normal b/c it takes longer for chemoreceptors to sense low [CO2]

Question 3

List the duration of breath hold from shortest to longest for normal and forced expiration and inspiration.

Answer 3

1. Forced expiration
2. Normal expiration
3. Normal inspiration
4. Forced inspiration

Question 4

How and when did TV, RR, and CO2 change during exercise? Explain.

Answer 4

• Distinct increase in TV
• Less distinct increase in RR (occurs when TV can’t increase anymore to keep up w/ O2 demand)
• CO2 stayed steady, then increased towards the end b/c hyperpnea

Question 5

What separates the lung from the ribcage?

Answer 5

Intrapleural space

Question 6

Which lung pressure changes w/ lung volume?

Answer 6

Alveolar pressure

Question 7

What is transpulmonary pressure? Equation?

Answer 7

P(tp) = alveolar pressure - intrapleural pressure

Question 8

What nerve initiates inspiration? What does it do?

Answer 8

Phrenic nerve induces contraction of diaphragm and muscles of the chest wall

Question 9

What conditions would cause an increase in the firing rate of the peripheral chemoreceptors?

Answer 9

• Hypoxia (decreased O2)
• Hypercapnia (increased CO2)
• Acidosis (decreased pH)

Question 10

Why did we collect only the very end of our TV in the respiratory lab?

Answer 10

Dead space gases are included in the beginning of expired air

Question 11

Central chemoreceptors are specifically sensitive to ____ in the extracellular space of the brain.

Answer 11

[H+]

Question 12

During intense exercise, venous plasma [CO2] will be ___ compared to resting values.

Answer 12

Higher

Question 13

What is the limiting factor for oxygen supply to the exercising tissues?

Answer 13

Gross amount of Hb bound to O2

Question 14

During moderate exercise, the [O2] in the venous blood supply is ___ than at rest.

Answer 14

Lower

Question 15

During moderate exercise, the [CO2] in the venous blood supply is ___ than at rest.

Answer 15

Higher