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1. D1: Extreme environments > L1. High altitude physiology > Flashcards

L1. High altitude physiology Flashcards

1
Q

What are the three key physiological responses to high altitude?

A

Erythrocytosis, pulmonary arterial vasoconstriction, and ventilatory acclimatization

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2
Q

Who described the quote ‘Humans are a sea-level design’?

A

Carlos Monge

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3
Q

What is erythrocytosis?

A

An increase in red blood cell production, often as a response to high altitude

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4
Q

How does high altitude affect pulmonary arterial pressure?

A

It increases due to hypoxic pulmonary vasoconstriction

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5
Q

What is the function of the Hypoxia Inducible Factor (HIF) pathway?

A

It regulates gene expression in response to low oxygen levels

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6
Q

What is chronic mountain sickness?

A

A condition characterized by excessive erythrocytosis, hypoventilation, and pulmonary hypertension

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7
Q

How do Tibetans differ from other high-altitude populations in terms of hemoglobin?

A

They have a lower hemoglobin concentration despite living at high altitude

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8
Q

What is Poiseuille’s Law and its relevance to high altitude?

A

It describes how blood viscosity affects cardiac work and vascular resistance

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9
Q

Why is ventilatory acclimatization considered advantageous?

A

It increases oxygen intake by raising ventilation at high altitude

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10
Q

What is the role of the carotid body in acclimatization?

A

It senses hypoxia and triggers ventilatory responses

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11
Q

What happens to alveolar PO2 and PCO2 during acclimatization?

A

PO2 decreases, and PCO2 decreases due to hyperventilation

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12
Q

How does erythrocytosis benefit oxygen transport at high altitude?

A

It increases oxygen-carrying capacity by raising red blood cell counts

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13
Q

What genetic mutation is associated with Tibetan adaptations to altitude?

A

EPAS1 mutations leading to lower hemoglobin levels

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14
Q

How does pulmonary vasoconstriction affect oxygenation?

A

It reduces oxygen delivery due to increased vascular resistance

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15
Q

What is the impact of prolonged high-altitude exposure on ventilatory sensitivity?

A

Ventilatory sensitivity to hypoxia is reduced over time

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16
Q

What is the relationship between high altitude and HIF activation?

A

HIF activation increases in response to hypoxia, promoting erythropoiesis and angiogenesis

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17
Q

How do Chuvash polycythemia patients respond to hypoxia?

A

They show heightened ventilatory and erythropoietic responses

18
Q

What was the Pike’s Peak Expedition significant for?

A

It provided the first detailed studies of ventilatory acclimatization

19
Q

How do horses and dogs adapt hematocrit levels during exercise?

A

By contracting their spleens to release more red blood cells

20
Q

What role does iron play in hypoxic adaptation?

A

Iron availability modulates the HIF pathway and pulmonary vascular responses

21
Q

What is the role of ventilatory set point at high altitude?

A

It regulates sensitivity to hypoxia and CO2 over prolonged exposure

22
Q

How does ventilatory acclimatization differ between lowlanders and high-altitude natives?

A

Lowlanders have enhanced acute hypoxic responses, while natives have blunted responses

23
Q

What is the function of EPAS1 in Tibetans?

A

It supports low hemoglobin levels without compromising oxygen delivery

24
Q

What is the effect of hyperventilation on blood gases at altitude?

A

It lowers PCO2, causing respiratory alkalosis

25
Q

What physiological process limits the rise in hemoglobin at high altitude?

A

Natural selection for efficiency rather than maximum oxygen carrying capacity

26
Q

What happens to pulmonary arterial pressure with acute hypoxia?

A

It increases, causing potential strain on the heart

27
Q

What are the advantages of ventilatory acclimatization?

A

Improved oxygen uptake and reduced CO2 levels

28
Q

What are the effects of sustained hypoxia on peripheral chemoreceptors?

A

Increased sensitivity to hypoxia and CO2

29
Q

What is the relationship between erythrocytosis and cardiac work?

A

Excessive erythrocytosis increases blood viscosity, raising cardiac workload

30
Q

What genetic evidence supports Tibetan adaptation to hypoxia?

A

Selection for EPAS1 and EGLN1 mutations in the HIF pathway

31
Q

What is the function of renal oxygen sensing in erythropoiesis?

A

Regulating erythropoietin production to match oxygen needs

32
Q

How does altitude training differ from permanent high-altitude adaptation?

A

Training induces temporary erythrocytosis; adaptation involves genetic changes

33
Q

What is the impact of high altitude on exercise performance?

A

Reduced VO2max and increased pulmonary vascular strain

34
Q

How do Andean populations differ in high-altitude adaptation?

A

They exhibit higher hemoglobin levels than Tibetans but similar adaptations

35
Q

What are the implications of chronic hypoxia for pulmonary health?

A

Increased risk of pulmonary hypertension and right ventricular strain

36
Q

How does ventilatory acclimatization progress over time?

A

Progressive increases in ventilation and chemoreceptor sensitivity

37
Q

What experimental evidence supports carotid body involvement in acclimatization?

A

Denervated animals fail to acclimatize to hypoxia

38
Q

What is the role of renal compensation in acclimatization?

A

Partial restoration of acid-base balance through bicarbonate excretion

39
Q

What does acclimatization achieve at cellular levels?

A

Enhanced mitochondrial efficiency and oxygen utilization

40
Q

What does the term ‘poikilocapnic hypoxia’ refer to?

A

Hypoxia with uncontrolled PCO2 levels, influencing ventilatory responses

1. D1: Extreme environments (6 decks)

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