Explain how the nervous system and endocrine system work together to maintain blood glucose concentration within normal limits following a carbohydrate-rich meal.

IB DP Biology Higher Level (2023 syllabus) — C3.1 Integration of body systems · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

1. The nervous system detects the rise in blood glucose through glucose receptors in the brain and beta cells in the islets of Langerhans that act as sensors.
2. The beta cells secrete insulin into the blood when glucose is high.
3. Insulin stimulates target cells – liver, muscle and adipose – to take up glucose; the liver also converts glucose to glycogen by glycogenesis, lowering blood glucose.
4. The hypothalamus and autonomic nervous system integrate the hormonal response, modulating pancreatic secretion and stimulating satiety, forming a negative‑feedback loop that restores glucose to the set point.

Examiner tips

  • Use the exact terms "beta cells", "insulin", "glycogenesis" and "negative feedback". Show the sequence: detection → insulin release → cellular uptake & glycogenesis → feedback. Keep each point short and to the point.

Common mistakes

  • Mixing up the roles of the nervous and endocrine systems (e.g., saying the nervous system secretes insulin). Omitting the negative‑feedback aspect or the role of the hypothalamus and autonomic nervous system.

Mark scheme (4 marks)

  1. The nervous system detects the rise in blood glucose via glucose receptors / beta cells in the islets of Langerhans act as sensors that respond directly to elevated blood glucose.
  2. Beta cells of the islets of Langerhans secrete insulin into the blood in response to high blood glucose.
  3. Insulin stimulates target cells (liver / muscle / adipose) to take up glucose, and the liver converts glucose to glycogen by glycogenesis, lowering blood glucose concentration.
  4. The nervous system (via the hypothalamus and autonomic nervous system) integrates the hormonal response by modulating pancreatic secretion and stimulating satiety signals, illustrating negative feedback regulation that restores blood glucose to the set point.

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