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Homeostasis: Question 10

Syllabus 14.1

Multiple choice A2 1 mark

The islets of Langerhans in the pancreas contain two main types of hormone-secreting cell. Each type directly detects blood glucose concentration itself and responds by changing its rate of hormone secretion, forming part of a negative feedback loop that controls blood glucose concentration.

Which statement correctly identifies these cell types, the hormone each secretes, and the change in blood glucose concentration that increases secretion of that hormone?

Choose an answer to check it, then compare with the worked solution below.
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Worked solution

Step 1: Recall the two islet cell types and their hormones

The islets of Langerhans contain α (alpha) cells, which secrete glucagon, and β (beta) cells, which secrete insulin. These two hormones have antagonistic (opposite) effects on blood glucose concentration: insulin lowers it, and glucagon raises it.

Step 2: Recall what stimulates each cell type to secrete more of its hormone

Both cell types directly detect blood glucose concentration:

  • β cells increase insulin secretion when blood glucose concentration rises (e.g. after a meal), since insulin’s role is to bring the raised concentration back down.
  • α cells increase glucagon secretion when blood glucose concentration falls (e.g. during fasting), since glucagon’s role is to raise the lowered concentration back up.

This reciprocal control, with each hormone opposing deviations in one direction, forms a negative feedback loop that keeps blood glucose concentration close to its set point.

Step 3: Evaluate each option

  • A: correct. α cells secrete glucagon (increased when glucose falls), β cells secrete insulin (increased when glucose rises).
  • B: incorrect. The hormones are swapped between the two cell types.
  • C: incorrect. The stimulus for each hormone is reversed; glucagon secretion increases when glucose falls, not rises, and insulin secretion increases when glucose rises, not falls.
  • D: incorrect, α and β cells secrete different hormones (glucagon and insulin respectively), not the same hormone.

Final answer

  • α (alpha) cells secrete glucagon, released more when blood glucose falls; β (beta) cells secrete insulin, released more when blood glucose rises, option A.