Analyse how the pulmonary and systemic circulations respond to increased oxygen demands during physical activity. (8 marks)
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Sample Answer
Overview Statement
- Pulmonary and systemic circulations demonstrate coordinated responses to increased oxygen demands during exercise.
- Key components include cardiac output, blood flow redistribution, and gas exchange efficiency.
- Both systems interact to maintain oxygen delivery while removing metabolic waste.
Metabolic Demand and Detection
- Increased muscle metabolism creates higher oxygen demand and CO₂ production.
- Chemoreceptors detect changed blood gas levels, triggering immediate cardiovascular responses.
- Neural signals initiate adjustments in both circulatory pathways simultaneously.
- Such detection mechanisms ensure rapid adaptation to exercise demands.
Pulmonary Circulation Adaptations
- Cardiac output to the lungs increases through elevated heart rate and stroke volume.
- More alveolar capillaries open, expanding the gas exchange surface area.
- Blood flow through lungs rises significantly while maintaining efficient oxygen uptake.
- Enhanced pulmonary flow directly influences oxygen availability for systemic distribution.
Systemic Circulation Redistribution
- Blood flow redistributes through selective vasoconstriction and vasodilation.
- Working muscles receive the majority of cardiac output during intense exercise.
- Non-essential organs experience reduced blood flow to prioritise active tissues.
- Redistribution mechanisms optimise oxygen delivery to areas of greatest need.
Venous Return Enhancement
- Muscle pump and respiratory pump work together to propel blood back to the heart.
- Deep breathing creates thoracic pressure changes that assist venous flow.
- Skeletal muscle contractions compress veins, pushing blood upward against gravity.
- Enhanced venous return maintains the increased cardiac output required during exercise.
Show Worked Solution
Sample Answer
Overview Statement
- Pulmonary and systemic circulations demonstrate coordinated responses to increased oxygen demands during exercise.
- Key components include cardiac output, blood flow redistribution, and gas exchange efficiency.
- Both systems interact to maintain oxygen delivery while removing metabolic waste.
Metabolic Demand and Detection
- Increased muscle metabolism creates higher oxygen demand and CO₂ production.
- Chemoreceptors detect changed blood gas levels, triggering immediate cardiovascular responses.
- Neural signals initiate adjustments in both circulatory pathways simultaneously.
- Such detection mechanisms ensure rapid adaptation to exercise demands.
Pulmonary Circulation Adaptations
- Cardiac output to the lungs increases through elevated heart rate and stroke volume.
- More alveolar capillaries open, expanding the gas exchange surface area.
- Blood flow through lungs rises significantly while maintaining efficient oxygen uptake.
- Enhanced pulmonary flow directly influences oxygen availability for systemic distribution.
Systemic Circulation Redistribution
- Blood flow redistributes through selective vasoconstriction and vasodilation.
- Working muscles receive the majority of cardiac output during intense exercise.
- Non-essential organs experience reduced blood flow to prioritise active tissues.
- Redistribution mechanisms optimise oxygen delivery to areas of greatest need.
Venous Return Enhancement
- Muscle pump and respiratory pump work together to propel blood back to the heart.
- Deep breathing creates thoracic pressure changes that assist venous flow.
- Skeletal muscle contractions compress veins, pushing blood upward against gravity.
- Enhanced venous return maintains the increased cardiac output required during exercise.