Structures and Functions in Living Organisms · 4 question types
Past paper frequency (2018 to 2024)
This topic accounts for approximately 16% of your exam marks.
Blood glucose regulation and temperature control are increasing in frequency; insulin/glucagon tested every series.
The three homeostatic systems covered here (or referenced from other topics) all use the same general structure:
| Variable | Receptor | Coordinator | Effector | Hormone(s) involved |
|---|---|---|---|---|
| Body temperature | Temperature receptors in skin and hypothalamus | Hypothalamus | Skin (sweat glands, arterioles, hair muscles), skeletal muscle (shivering) | None directly; nervous coordination |
| Blood glucose | Cells in the pancreas | Pancreas | Liver, muscles | Insulin (lowers), glucagon (raises) |
| Blood water content | Osmoreceptors in hypothalamus | Hypothalamus → pituitary gland | Kidneys (collecting ducts) | ADH |
In each case the principle is the same: detect the change, respond with the opposite, restore the norm. Once you understand this pattern, every homeostatic system in the body fits the same template.