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

IB DP Biology Standard 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)

Rising blood glucose after a carbohydrate‑rich meal is sensed by glucose receptors in the blood and by the beta cells of the pancreas. The beta cells respond by secreting insulin into the bloodstream. Insulin acts on liver cells (hepatocytes) and on muscle cells, stimulating the uptake of glucose and its conversion into glycogen (glycogenesis). The nervous system, through the autonomic nervous system and the hypothalamus, also contributes: it regulates satiety and gastric activity and stimulates insulin release via the vagus nerve, thereby integrating both systems to keep blood glucose within a normal range.

Examiner tips

  • Mention the glucose receptors and beta cells first; link insulin secretion to the pancreas.
  • Show insulin’s action on liver and muscle and the process of glycogenesis.
  • Include the autonomic nervous system’s role via the vagus nerve and hypothalamic regulation.
  • Use the exact terminology: beta cells, insulin, hepatocytes, glycogenesis, autonomic nervous system.

Common mistakes

  • Confusing glucagon with insulin; stating that glucagon is released after a meal.
  • Omitting the role of the nervous system or the vagus nerve.
  • Using vague terms like "the body" instead of specifying liver and muscle cells.

Mark scheme (4 marks)

  1. Rising blood glucose is detected by receptors / beta cells in the islets of Langerhans in the pancreas
  2. Beta cells secrete insulin into the blood / respond by releasing insulin as a hormonal signal
  3. Insulin acts on liver cells / hepatocytes and muscle cells, stimulating uptake of glucose and its conversion to glycogen (glycogenesis)
  4. The nervous system (autonomic / hypothalamus) also contributes by regulating satiety / gastric activity / stimulating insulin release via the vagus nerve, illustrating integration of both systems

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