Which one of the following is NOT true in the process of acclimatization to high altitude?
- Respiratory alkalosis
- Increased 2,3-DPG in RBC
- Rise in pH of cerebrospinal fluid
- Increased cytochrome oxidase in tissues
Rephrasing the question:
What happens during altitude acclimatization?
Rise in pH of cerebrospinal fluid does NOT happen during acclimatization (option 3).
The human body adapts to high altitude both in the short term and in the long term.
In the short term, the lack of oxygen is sensed by the carotid bodies (located in the carotid artery), which causes an increase in the breathing depth and rate (hyperpnea), which then causes respiratory alkalosis. The pulse rate and cardiac output increase, and non-essential bodily functions are suppressed, resulting in a decline in food digestion efficiency.
Full acclimatization happens over a time span of days to weeks. Renal excretion of bicarbonate increases so that increased respiration can provide more oxygen without alkalosis. This is accompanied by other changes that increase oxygen delivery to tissues: increased haematocrit (RBC number) and haemoglobin, a higher concentration of capillaries in skeletal muscle tissue, increased myoglobin, and an increase in 2,3-DPG (an allosteric effector of haemoglobin that promotes release of oxygen to tissues).
Moreover, aerobic respiration is increased over anaerobic respiration. So we get lower lactate production, but increased mitochondrial activity and increased aerobic enzyme concentration (like cytochrome c oxidase, the last enzyme in the electron transport chain in mitochondria).
While the pH of cerebrospinal fluid does increase slightly at high altitude, it drops to normal as acclimatization happens.