Thermoregulation

This lesson covers thermoregulation -- the control of body temperature -- as required by the Edexcel A-Level Biology specification (9BI0), Topic 9 -- Control Systems. You need to understand the mechanisms by which endotherms maintain a constant core temperature and how the hypothalamus acts as the thermoregulatory centre.

---

Why Regulate Body Temperature?

Maintaining a stable core body temperature (approximately 37°C in humans) is essential because:

• Enzymes have an optimum temperature. At temperatures above the optimum, the tertiary structure of enzyme proteins is disrupted (denaturation), reducing the rate of metabolic reactions. At temperatures below the optimum, molecules have less kinetic energy and the rate of enzyme-substrate collisions decreases.
• Extreme temperature changes can damage cell membranes (increased fluidity at high temperatures; rigidity at low temperatures).
• The function of proteins such as haemoglobin and membrane transport proteins depends on temperature-sensitive conformations.

---

Endotherms and Ectotherms