L1. High altitude physiology Flashcards
What are the three key physiological responses to high altitude?
Erythrocytosis, pulmonary arterial vasoconstriction, and ventilatory acclimatization
Who described the quote ‘Humans are a sea-level design’?
Carlos Monge
What is erythrocytosis?
An increase in red blood cell production, often as a response to high altitude
How does high altitude affect pulmonary arterial pressure?
It increases due to hypoxic pulmonary vasoconstriction
What is the function of the Hypoxia Inducible Factor (HIF) pathway?
It regulates gene expression in response to low oxygen levels
What is chronic mountain sickness?
A condition characterized by excessive erythrocytosis, hypoventilation, and pulmonary hypertension
How do Tibetans differ from other high-altitude populations in terms of hemoglobin?
They have a lower hemoglobin concentration despite living at high altitude
What is Poiseuille’s Law and its relevance to high altitude?
It describes how blood viscosity affects cardiac work and vascular resistance
Why is ventilatory acclimatization considered advantageous?
It increases oxygen intake by raising ventilation at high altitude
What is the role of the carotid body in acclimatization?
It senses hypoxia and triggers ventilatory responses
What happens to alveolar PO2 and PCO2 during acclimatization?
PO2 decreases, and PCO2 decreases due to hyperventilation
How does erythrocytosis benefit oxygen transport at high altitude?
It increases oxygen-carrying capacity by raising red blood cell counts
What genetic mutation is associated with Tibetan adaptations to altitude?
EPAS1 mutations leading to lower hemoglobin levels
How does pulmonary vasoconstriction affect oxygenation?
It reduces oxygen delivery due to increased vascular resistance
What is the impact of prolonged high-altitude exposure on ventilatory sensitivity?
Ventilatory sensitivity to hypoxia is reduced over time
What is the relationship between high altitude and HIF activation?
HIF activation increases in response to hypoxia, promoting erythropoiesis and angiogenesis
How do Chuvash polycythemia patients respond to hypoxia?
They show heightened ventilatory and erythropoietic responses
What was the Pike’s Peak Expedition significant for?
It provided the first detailed studies of ventilatory acclimatization
How do horses and dogs adapt hematocrit levels during exercise?
By contracting their spleens to release more red blood cells
What role does iron play in hypoxic adaptation?
Iron availability modulates the HIF pathway and pulmonary vascular responses
What is the role of ventilatory set point at high altitude?
It regulates sensitivity to hypoxia and CO2 over prolonged exposure
How does ventilatory acclimatization differ between lowlanders and high-altitude natives?
Lowlanders have enhanced acute hypoxic responses, while natives have blunted responses
What is the function of EPAS1 in Tibetans?
It supports low hemoglobin levels without compromising oxygen delivery
What is the effect of hyperventilation on blood gases at altitude?
It lowers PCO2, causing respiratory alkalosis
What physiological process limits the rise in hemoglobin at high altitude?
Natural selection for efficiency rather than maximum oxygen carrying capacity
What happens to pulmonary arterial pressure with acute hypoxia?
It increases, causing potential strain on the heart
What are the advantages of ventilatory acclimatization?
Improved oxygen uptake and reduced CO2 levels
What are the effects of sustained hypoxia on peripheral chemoreceptors?
Increased sensitivity to hypoxia and CO2
What is the relationship between erythrocytosis and cardiac work?
Excessive erythrocytosis increases blood viscosity, raising cardiac workload
What genetic evidence supports Tibetan adaptation to hypoxia?
Selection for EPAS1 and EGLN1 mutations in the HIF pathway
What is the function of renal oxygen sensing in erythropoiesis?
Regulating erythropoietin production to match oxygen needs
How does altitude training differ from permanent high-altitude adaptation?
Training induces temporary erythrocytosis; adaptation involves genetic changes
What is the impact of high altitude on exercise performance?
Reduced VO2max and increased pulmonary vascular strain
How do Andean populations differ in high-altitude adaptation?
They exhibit higher hemoglobin levels than Tibetans but similar adaptations
What are the implications of chronic hypoxia for pulmonary health?
Increased risk of pulmonary hypertension and right ventricular strain
How does ventilatory acclimatization progress over time?
Progressive increases in ventilation and chemoreceptor sensitivity
What experimental evidence supports carotid body involvement in acclimatization?
Denervated animals fail to acclimatize to hypoxia
What is the role of renal compensation in acclimatization?
Partial restoration of acid-base balance through bicarbonate excretion
What does acclimatization achieve at cellular levels?
Enhanced mitochondrial efficiency and oxygen utilization
What does the term ‘poikilocapnic hypoxia’ refer to?
Hypoxia with uncontrolled PCO2 levels, influencing ventilatory responses
