A long-distance cyclist has been competing in a 100 kilometre race for 2.5 hours.
Explain how the digestive, endocrine, and circulatory systems interact to sustain energy supply to the muscular system during this prolonged activity. (5 marks)
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Sample Answer
Digestive system:
- After 2.5 hours, glycogen stores are depleting and the body relies more on consumed nutrients.
- As a result, glucose from race nutrition absorbs into the bloodstream to maintain energy levels.
Endocrine system:
- Hormones regulate energy metabolism through insulin and glucagon balance.
- When blood glucose drops, the pancreas reduces insulin secretion and increases glucagon.
- This hormonal change triggers the liver to convert stored glycogen to glucose.
Endocrine-Circulatory Interaction:
- During prolonged cycling, cortisol and adrenaline are released into the bloodstream.
- These hormones cause fatty acids to mobilise from fat stores as additional energy.
- Consequently, muscles can spare limited glycogen stores.
Circulatory System Delivery:
- Blood vessels transport nutrients (glucose, fatty acids) and oxygen to working muscles.
- This continuous delivery enables sustained energy production throughout the race.
- Blood flow increases to active muscles through vasodilation while non-essential areas receive less blood.
System Integration:
- The interaction between these systems ensures optimal nutrient delivery to maintain performance.
- The digestive system provides fuel while the endocrine system controls its release.
- Meanwhile, the circulatory system delivers nutrients precisely where needed for sustained muscular work.
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Sample Answer
Digestive system:
- After 2.5 hours, glycogen stores are depleting and the body relies more on consumed nutrients.
- As a result, glucose from race nutrition absorbs into the bloodstream to maintain energy levels.
Endocrine system:
- Hormones regulate energy metabolism through insulin and glucagon balance.
- When blood glucose drops, the pancreas reduces insulin secretion and increases glucagon.
- This hormonal change triggers the liver to convert stored glycogen to glucose.
Endocrine-Circulatory Interaction:
- During prolonged cycling, cortisol and adrenaline are released into the bloodstream.
- These hormones cause fatty acids to mobilise from fat stores as additional energy.
- Consequently, muscles can spare limited glycogen stores.
Circulatory System Delivery:
- Blood vessels transport nutrients (glucose, fatty acids) and oxygen to working muscles.
- This continuous delivery enables sustained energy production throughout the race.
- Blood flow increases to active muscles through vasodilation while non-essential areas receive less blood.
System Integration:
- The interaction between these systems ensures optimal nutrient delivery to maintain performance.
- The digestive system provides fuel while the endocrine system controls its release.
- Meanwhile, the circulatory system delivers nutrients precisely where needed for sustained muscular work.