Explain how the cardiovascular system adapts to exercise at altitude (2500 metres) over both short-term (24 - 48 hours) and long-term (3+ weeks) periods. (5 marks)
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Sample Answer
- Reduced oxygen pressure at altitude triggers immediate cardiovascular responses within 24-48 hours.
- Heart rate increases because the body needs to circulate blood faster to compensate for lower oxygen content.
- Cardiac output also rises through increased stroke volume, ensuring tissues receive adequate oxygen supply.
- These short-term changes maintain oxygen delivery to vital organs despite the thinner air.
- Breathing rate accelerates in response to chemoreceptors detecting lower blood oxygen levels.
- After several days, low oxygen levels stimulate the kidneys to produce EPO (erythropoietin).
- EPO signals bone marrow to increase red blood cell production, which begins the long-term adaptation process.
- Over 3-4 weeks, red blood cell count rises significantly, enhancing the blood’s oxygen-carrying capacity.
- Increased haemoglobin concentration results from these higher red blood cell numbers.
- More haemoglobin molecules enable better oxygen binding from each breath of thin air.
- Blood vessels in tissues also increase through capillarisation, improving oxygen delivery at the cellular level.
- Long-term adaptations therefore compensate for reduced atmospheric oxygen, allowing sustained performance at altitude.
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Sample Answer
- Reduced oxygen pressure at altitude triggers immediate cardiovascular responses within 24-48 hours.
- Heart rate increases because the body needs to circulate blood faster to compensate for lower oxygen content.
- Cardiac output also rises through increased stroke volume, ensuring tissues receive adequate oxygen supply.
- These short-term changes maintain oxygen delivery to vital organs despite the thinner air.
- Breathing rate accelerates in response to chemoreceptors detecting lower blood oxygen levels.
- After several days, low oxygen levels stimulate the kidneys to produce EPO (erythropoietin).
- EPO signals bone marrow to increase red blood cell production, which begins the long-term adaptation process.
- Over 3-4 weeks, red blood cell count rises significantly, enhancing the blood’s oxygen-carrying capacity.
- Increased haemoglobin concentration results from these higher red blood cell numbers.
- More haemoglobin molecules enable better oxygen binding from each breath of thin air.
- Blood vessels in tissues also increase through capillarisation, improving oxygen delivery at the cellular level.
- Long-term adaptations therefore compensate for reduced atmospheric oxygen, allowing sustained performance at altitude.