FreeScienceLessons · AQA BiologyThermoregulation and Body Temperature Control
Key facts
Thermoregulation — core mechanism
Core body temperature maintained at 37°C — the optimum for enzymes.
Monitored by the thermoregulatory centre in the hypothalamus (brain).
Receptors in the hypothalamus detect blood temperature. Skin receptors detect external temperature.
Responses are automatic (involuntary) via the nervous and hormonal systems.
Responses to temperature changes
Too hot: (1) Vasodilation — blood vessels near skin surface widen → more blood to skin surface → more heat lost by radiation. (2) Sweating — water evaporates from skin → takes heat energy away. (3) Hairs lie flat (erector muscles relax).
Too cold: (1) Vasoconstriction — blood vessels near skin surface narrow → less blood → less heat lost. (2) Shivering — muscles contract rapidly → respiration releases heat energy. (3) Hairs stand up (erector muscles contract) → trap insulating air layer.
Exam questions — 3 questions · 11 marks
⚡ Extended questions included. Read the hint. Write in full sentences. AI marks against the AQA mark scheme.
1 markVasodilation effectAQA 8461 P2 style
How does vasodilation help cool the body when it is too hot?
A Blood vessels widen, increasing blood flow to the skin surface, which increases heat loss by radiation
B Blood vessels widen, allowing sweat to pass through them more easily
C Blood vessels widen, reducing blood pressure and slowing the heart rate
D Blood vessels widen, causing the skin to contract and trap heat
1 markShivering mechanismAQA 8461 style
Why does shivering help raise body temperature?
A Shivering increases blood flow to the muscles
B Rapid muscle contractions during shivering require respiration, which releases heat energy as a by-product
C Shivering causes the hairs to stand up, trapping more air
D Shivering reduces blood flow to the skin surface to conserve heat
A person moves from a cold room into a warm environment. Describe the changes that occur in the skin to help maintain a constant core body temperature. (4 marks)