Lesson overview
Homeostasis: How does your body keep its inside conditions steady?
Walk a model person from a warm room into a cold porch and back, and read the core and the skin temperature on a monitor: the skin changes a lot, the core hardly at all. For the Supplement, find the parts of the skin, follow the impulses of negative feedback and switch one response off at a time; then follow the blood glucose concentration through a meal and find the hormone that brings it back down.
Suggested sequence
- Lesson 1 · A warm room and a cold porch. Homeostasis as a constant internal environment, read from the core and the skin temperature; (Supplement) vasoconstriction, shivering, sweating and vasodilation. Read together (10–15 min), show or explore the experiment (10 min), practise with self-checking (15–20 min).
- Lesson 2 · Skin and negative feedback. (Supplement) The parts of the skin; negative feedback with reference to a set point; the role of the brain, and what sweating and shivering do. Read together (10–15 min), show or explore the experiment (10 min), practise with self-checking (15–20 min).
- Lesson 3 · Blood glucose. Insulin decreases the blood glucose concentration; (Supplement) the liver, insulin and glucagon, and the treatment of Type 1 diabetes. Read together (10–15 min), show or explore the experiment (10 min), practise with self-checking (15–20 min).
- End of module · final check. 6 new questions, 20–30 min, without hints or notes; pupils check their answers once they have answered them all.
- One to two weeks later · return questions. 8 questions, 15 min, lesson closed.
Learning goals
Part 1: A warm room and a cold porch
- Describe homeostasis as the maintenance of a constant internal environment (14.4.1)
- Supplement: describe the maintenance of a constant internal body temperature in the cold in terms of insulation, shivering and the vasoconstriction of arterioles supplying skin surface capillaries (S14.4.7, S14.4.8)
- Supplement: describe the maintenance of a constant internal body temperature in the warm in terms of sweating and the vasodilation of arterioles supplying skin surface capillaries (S14.4.7, S14.4.8)
Part 2: Skin and negative feedback
- Supplement: identify in diagrams and images of the skin: hairs, hair erector muscles, sweat glands, receptors, sensory neurones, blood vessels and fatty tissue (S14.4.6)
- Supplement: explain the concept of homeostatic control by negative feedback with reference to a set point, and the role of the brain in temperature control (S14.4.3, S14.4.7)
Part 3: Blood glucose
- State that insulin decreases blood glucose concentration (14.4.2)
- Supplement: describe the control of the glucose concentration of the blood by the liver and the roles of insulin and glucagon from the pancreas (S14.4.4)
- Supplement: outline the treatment of Type 1 diabetes (S14.4.5)
Misconceptions to listen for
- “Homeostasis keeps every condition in the body exactly the same.” — Conditions change a little and are brought back: the core temperature dipped from 37.0 to 36.8 °C in the porch and came back up.
- “The skin temperature, because the skin is the outside of the body.” — The skin temperature fell by 8.5 °C. The temperature kept near 37 °C is the core temperature, deep inside.
- “0.1 °C.” — That is the fall in the core temperature. The skin fell much more.
- “Shivering cools the body down.” — Shivering releases heat: the muscles respire faster as they contract.
- “Sweat is cold, so it cools the skin.” — Sweat comes out at about skin temperature. It cools the skin as it evaporates.
- “The capillaries move deeper into the skin.” — Blood vessels do not move. The arterioles supplying the surface capillaries become narrower.
- “It shows that the skin is better at homeostasis than the core.” — The skin temperature changed a lot. The core temperature is the one kept constant.
- “(a) 2 °C.” — The core graph runs from 36 to 38 °C: each numbered line is 0.5 °C and each thin line 0.1 °C. 37.0 − 36.8 = 0.2 °C.
- “The blood vessels move away from the skin.” — Vessels do not move: the arterioles supplying the surface capillaries become narrower.
- “The capillaries move closer to the surface.” — Capillaries do not move. The arterioles supplying them widen, so more blood flows through them.
Scope
Homeostasis (14.4.1–14.4.8): homeostasis as the maintenance of a constant internal environment; insulin decreases the blood glucose concentration; and, for the Supplement, homeostatic control by negative feedback with reference to a set point; the control of the blood glucose concentration by the liver and the roles of insulin and glucagon; an outline of the treatment of Type 1 diabetes; the hairs, hair erector muscles, sweat glands, receptors, sensory neurones, blood vessels and fatty tissue of the skin, identified in diagrams and images; and the maintenance of a constant internal body temperature in mammals by insulation, sweating, shivering and the role of the brain, and by vasodilation and vasoconstriction of the arterioles supplying the skin surface capillaries. Hormones, glands and adrenaline are in the module on hormones; neurones and the reflex arc in the module on nerves and reflexes; the kidney and water balance in the module on excretion. Type 2 diabetes, insulin doses and any medical advice are not covered here.