lecture 21

Question 1

What determines hemoglobin oxygen saturation?

Answer 1

Partial pressure of O₂ (PO₂)
↑ PO₂ → ↑ saturation
↓ PO₂ → ↓ saturation

Question 2

How does oxygen saturation relate to oxygen content of bloo

Answer 2

O₂ saturation reflects how much O₂ is bound to hemoglobin
Since most O₂ is carried by Hb:
→ Higher saturation = higher O₂ content

Question 3

How does exercise affect the arteriovenous O₂ difference?

Answer 3

Exercise ↑ muscle O₂ demand
More O₂ is extracted from blood
↓ venous O₂
→ ↑ a-v̄O₂ difference

Question 4

What is the typical oxygen saturation at sea level?

Answer 4

~98%
Slightly lower at higher altitude (e.g., Calgary)

Question 5

What is the shape of the oxygen dissociation curve and why is it important?

Back:

Answer 5

S-shaped (sigmoidal)
Allows:
Easy O₂ loading in lungs (plateau)
Easy O₂ unloading in tissues (steep portion

Question 6

What is the Bohr effect?

Answer 6

↑ CO₂ and ↑ H⁺ (↓ pH)
Causes hemoglobin to decrease affinity for O₂
Leads to right shift of oxygen–hemoglobin dissociation curve
Results in more oxygen being released to active tissues (e.g., exercising muscle)

Question 7

What is a left shift of the oxygen dissociation curve? haldane effect

Answer 7

↑ Hemoglobin affinity for O₂
Caused by: ↑ pH, ↓ CO₂, ↓ temperature
Results in less O₂ released to tissues
Promotes O₂ loading in lungs

Question 8

What regulates ventilation

Answer 8

Neural factors (brain/respiratory center)
Humoral factors (CO₂, H⁺, O₂)

Question 9

How does breathing control differ at rest vs exercise?

Answer 9

Rest: humoral control (CO₂, H⁺) dominates
Exercise: neural inputs strongly increase ventilatio

Question 10

What are neural factors that regulate ventilation?

Back:

Answer 10

Motor cortex (voluntary control)
Stretch receptors (lungs/airways)
Proprioceptors (muscles/joints)
Respiratory center rhythm
Emotional/stress signals

Question 11

“At rest, ventilation is primarily controlled by humoral (chemical) factors, while during exercise neural inputs dominate; psychological stress can also increase ventilation via sympathetic activation and reduced vagal tone.”

Answer 11

Located in the medulla (brainstem)
Detect:
↑ CO₂
↓ pH
Help regulate ventilation based on blood CO₂ (via brain fluid changes)

Question 12

What are peripheral chemoreceptors and what do they detect?

Answer 12

Located in:
Carotid bodies (neck)
Aortic bodies (heart area)
Detect:
↓ PO₂
↑ CO₂
↓ pH
Monitor arterial blood gases directly

Question 13

What is the main role of PaCO₂ and H⁺ in breathing control?

Answer 13

Primary drivers of ventilation at rest
↑ PaCO₂ or ↑ H⁺ → ↑ ventilation
Strong influence on cardiorespiratory control

Question 14

How do humoral and neural factors interact in respiratory control?

Answer 14

At rest: humoral (CO₂, H⁺) dominates
Vagal tone helps keep HR low (neural control)
During exercise: both humoral + neural factors increase ventilation

Question 15

What controls ventilation at rest?

Answer 15

Mainly humoral factors
↑ PaCO₂
↑ H⁺ (pH control)
These regulate cardiorespiratory function at rest

Question 16

What are the phases of ventilation during constant-load exercise?

and waat are they contolled by

Answer 16

Anticipation (Neural)
Exponential rise (Neural + Humoral)
Steady-state (Neural + Humoral)
Recovery (Neural first, Humoral second)

Question 17

Front:
How does recovery of ventilation occur after exercise

Answer 17

Neural factors decrease first
Humoral factors (CO₂, H⁺) take longer to return to normal
Ventilation stays elevated briefly after stopping exercise

Question 18

What does it mean that the respiratory system is “overbuilt” in untrained individuals?

Answer 18

The lungs have more capacity than needed for exercise
They are usually not the limiting factor in performance
Training has little effect on lung function compared to heart and muscles