Cardiorespiratory Responses to High Altitude Hypoxia in Geese

Question 1

What happens to oxygen supply at high altitudes?

Answer 1

• Decreased air density (increased demand for O2)
• Decreased PO2 (decrease the supply of O2)

Question 2

What are some Avian Exaptations?

Answer 2

• Tolerate Hypocapnia (decrease PCO2)
• Very Thin and strong Gas Exchange surface
• Cross-current gas exchange
• Large Hearts: cerebral perfusion is insensitive to hypocapnia
• High Capillarity: small muscle fibers (decrease diffusion distance)
• High Aerobic Capacity: Fast-contracting aerobic (TYPE IIA) fibers in flight muscle

Question 3

What cardiovascular changes accompany hypoxia exposure and regulate O2 delivery in the oxygen transport cascade of bar-headed geese specialized for high-altitude migration?

Answer 3

• Increased hemoglobin - O2 affinity
• Larger Hearts
• More blood vessels
• mitochondria are closer to blood vessels
• more mitochondria

Question 4

What ventilatory changes accompany hypoxia exposure and ensure blood-O2 loading for the oxygen transport cascade in bar-headed geese specialized for high altitude migration?

Answer 4

• More effective breathing patterns
• Enhancements in Diffusion or Mass O2 transport

Question 5

How does Rearing Altitude influence the Cardiovascular and Respiratory Response to Hypoxia in Bar-Headed Geese?

Answer 5

• HVR high altitude b-h geese is larger than low altitude b-h geese
• high altitude bar-headed geese have higher blood O2-saturation at given level of PaO2
• All birds maintain oxygen consumption throughout hypoxia
• All birds increase perfusion during hypoxia at similar arterial partial pressure - Oxygen (PaO2)

Question 6

Do High altitude birds with different altitudinal life histories maintain oxygen supply similarly?

Answer 6

All Birds
- Similar O2 saturation
- Maintain Oxygen Consumption throughout hypoxia exposure
- Increase Cardiac Output by 2-2.5 fold during hypoxia
Andean Geese
- Do not increase total ventilation during hypoxia
- Increase Lung O2 extraction progressively during hypoxia
- increase stroke volume 2-fold during hypoxia

Question 7

Compare the Hypoxic Ventilatory Response (HVR) of Andean Geese and Bar-Headed Geese

Answer 7

Andean
- Lung O2 extraction increases
- Stroke Volume 2-fold increase
- no increase in ventilation
Bar-headed Geese
- increases the HR during hypoxia
- enhanced O2 carrying capacity

Question 8

Compare the Hypercapnic Ventilatory Response of Andean Geese and Bar-headed Geese

Answer 8

Same
- Increase perfusion during hypoxia
Andean
- Increase Stroke Volume
Bar-headed
- Plastic (changes based on altitude)
- enhanced O2 carrying capacity
- Responds to hypoxia at more severe levels