Thermoregulation

🌡 Thermoregulation (Triple Science only)

Thermoregulatory Centre

• Found in the brain.

• Monitors and controls body temperature (~37 °C).

• Contains receptors that detect temperature of blood.

• Skin also has temperature receptors → send impulses via sensory neurons to the brain.

🔺 If body temperature is too high

1. Sweat glands release sweat → sweat evaporates → transfers heat energy away → cools body.

2. Vasodilation:

   • Blood vessels supplying skin capillaries dilate (widen).

   • More blood flows near skin surface.

   • More heat lost to environment.

🔻 If body temperature is too low

1. Vasoconstriction:

   • Blood vessels supplying skin capillaries constrict (narrow).

   • Less blood flows near skin surface → less heat lost.

2. Shivering:

   • Muscles contract rapidly.

   • Muscle contractions require energy from respiration → Increased rate of respiration

   • Respiration is an exothermic reaction

   • Releases heat → warms body.

3. Sweating stops → prevents further heat loss.

⚖ Key principle: Negative Feedback

• Thermoregulatory centre detects change from normal (37 °C).

• Sends signals to reverse the change.

• Brings temperature back to normal → example of homeostasis.

✅ Exam tip: You must know the words vasodilation (too hot) and vasoconstriction (too cold) and be able to explain how they change blood flow and heat transfer.