Question 1
Paper 4 short-answer style1 markDefine homeostasis. (1 mark)
Model answer
Homeostasis is the maintenance of a constant internal environment.
Why this scores
One mark for 'maintaining a constant internal environment'.
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Detailed notes on Coordination and Response for Cambridge IGCSE Biology, covering key concepts, explanations, examples, and exam-focused revision points.
Keeping inside steady. Blood glucose, body temperature, water — all controlled by NEGATIVE FEEDBACK.
Mapped to the Cambridge IGCSE 0610 syllabus (2026-2028).
Internal environment kept constant despite outside changes. Negative feedback is the mechanism.
Definition. Homeostasis = maintaining a CONSTANT INTERNAL ENVIRONMENT in cells and body fluids.
What's controlled?
Why it matters. Cells (especially enzymes) work in a NARROW range of conditions:
Negative feedback — the universal mechanism.
Change detected → response triggered → response REVERSES the change → conditions return to normal.
It's like a thermostat: room gets too cold → heater turns on → room warms up → heater turns off.
The four parts of any feedback loop:
Worked qualitative. Why is normal body temperature ~37°C, not, say, 25°C or 50°C?
Cambridge tip. Always mention NEGATIVE FEEDBACK. Cambridge marks the term.
Insulin lowers (after meal); glucagon raises (between meals). Both from pancreas.
Why glucose matters. Cells need glucose for respiration. But too much in blood is harmful (organs damaged); too little starves the brain (can cause unconsciousness).
After a meal — glucose rises.
Between meals / during exercise — glucose falls.
Diabetes.
Type 1 diabetes:
Type 2 diabetes:
Worked qualitative. Why is glucose in urine a sign of diabetes?
Cambridge tip. Memorise BOTH insulin AND glucagon. Cambridge often gives a graph and asks you to explain its dips and peaks.
Sweat + vasodilation cool. Shiver + vasoconstriction warm. Hairs adjust insulation.
Set point: ~37°C (normal core body temp).
When too HOT — body cools by:
1. Sweating.
2. Vasodilation.
3. Hair lying flat.
4. Behavioural responses.
When too COLD — body warms by:
1. Shivering.
2. Vasoconstriction.
3. Hair standing up.
4. Behavioural responses.
Skin = the main thermoregulatory organ. Sensors in skin AND brain detect temperature. Hypothalamus (in the brain) coordinates the response.
Worked qualitative. Why does drinking ice water 'cool you down' less than you might expect?
Cambridge tip. Always pair the response with the MECHANISM — not just 'sweat = cooling' but 'sweat evaporates → takes heat away'.
Verbatim phrases and definitions Cambridge mark schemes credit.
Homeostasis appears every Paper 4 (10-15 marks). Common formats: blood glucose graphs, temperature regulation diagrams, define negative feedback. Examiner reports flag students missing glucagon, saying skin vessels 'move', and confusing vasodilation/constriction.
Sources: Cambridge IGCSE Biology 0610 syllabus 2026-2028 (14.4); 0610/42 Oct/Nov 2024 — Q13 (homeostasis); 0610 Examiner Reports 2022-2024. Last reviewed 2026-05-07.
Step-by-step solutions to past-paper-style questions on homeostasis, written exactly the way a tutor would explain them at the board.
Question
Define homeostasis and give two examples of conditions that are kept constant.
Step-by-step solution
Step 1
Homeostasis is the maintenance of a constant internal environment, despite changes in the surroundings.
Step 2
Example 1: the blood glucose concentration is kept constant.
Step 3
Example 2: the body temperature is kept constant (about 37 °C in humans). (Water and ion content are also controlled.)
Answer
Homeostasis is keeping the internal environment constant. Examples: blood glucose concentration and body temperature.
Question
Name the hormone responsible for each: (a) lowering blood glucose; (b) raising blood glucose. State which gland produces them.
Step-by-step solution
Step 1
(a) Lowering blood glucose → insulin, from the pancreas.
Step 2
(b) Raising blood glucose → glucagon, from the pancreas.
Answer
Insulin lowers blood glucose; glucagon raises it. Both are made by the pancreas.
Examiner tip
Both hormones come from the pancreas; they have opposite effects, which is how the level is kept steady.
Question
Explain how the body brings the blood glucose level back to normal after it has risen (after a meal) and after it has fallen (during exercise).
Step-by-step solution
Step 1
After a meal (glucose rises): the pancreas releases insulin.
Step 2
Insulin makes the liver and muscle cells take up glucose and store it as glycogen, so the blood glucose level falls back to normal.
Step 3
During exercise (glucose falls): the pancreas releases glucagon.
Step 4
Glucagon makes the liver break down glycogen into glucose, which is released into the blood, so the level rises back to normal.
Answer
High glucose: pancreas releases insulin → liver/muscles store glucose as glycogen. Low glucose: pancreas releases glucagon → liver breaks glycogen back to glucose.
Examiner tip
Cambridge marks BOTH directions. Many students describe only insulin and forget glucagon.
Question
Describe how the body responds when it is (a) too hot and (b) too cold.
Step-by-step solution
Step 1
(a) Too hot: sweating increases — water in sweat evaporates from the skin, taking heat away.
Step 2
The blood vessels supplying the skin capillaries widen (vasodilation), so more blood flows near the surface and more heat is lost.
Step 3
(b) Too cold: shivering occurs — the muscles contract rapidly, and the respiration this needs releases heat.
Step 4
The blood vessels supplying the skin capillaries narrow (vasoconstriction), so less blood flows near the surface and less heat is lost.
Answer
Too hot: more sweating and vasodilation → more heat lost. Too cold: shivering and vasoconstriction → heat generated and less heat lost.
Question
Explain what is meant by negative feedback, using the control of body temperature as an example.
Step-by-step solution
Step 1
In negative feedback, a change in a condition triggers a response that reverses the change, bringing the condition back to its normal level.
Step 2
If the body becomes too hot, this change is detected, and responses such as sweating and vasodilation are triggered to cool the body down.
Step 3
If the body becomes too cold, responses such as shivering and vasoconstriction are triggered to warm the body up.
Step 4
In each case the response opposes the change, so the temperature is kept close to the normal value of about 37 °C.
Answer
Negative feedback means a change triggers a response that reverses it. Too hot → cooling responses; too cold → warming responses — so the temperature is kept near normal.
Examiner tip
The key idea is 'the response reverses/opposes the change' — that is what makes it negative feedback.
Question
A person with Type 1 diabetes cannot produce enough insulin. Explain the problem this causes and how it is treated.
Step-by-step solution
Step 1
Without enough insulin, the body cannot lower the blood glucose after a meal.
Step 2
So the blood glucose concentration rises too high, and glucose may appear in the urine.
Step 3
A high blood glucose level is harmful, and the person may feel tired or thirsty.
Step 4
It is treated by injecting insulin (especially before meals), and by controlling the diet (limiting sugary foods), so the blood glucose is kept within safe limits.
Answer
Without insulin, blood glucose rises too high after meals. It is treated by injecting insulin and by controlling the diet, keeping blood glucose within safe limits.
Examiner tip
Type 1 diabetes = too little insulin → high blood glucose; treated with insulin injections and diet control.
High-scoring sample answers for homeostasis on the Cambridge IGCSE 0610 paper, with examiner-style notes mapping each response to the mark scheme and assessment objectives.
Define homeostasis. (1 mark)
Model answer
Homeostasis is the maintenance of a constant internal environment.
Why this scores
One mark for 'maintaining a constant internal environment'.
Name the hormone that lowers blood glucose, and the gland that produces it. (2 marks)
Model answer
The hormone is insulin, and it is produced by the pancreas.
Why this scores
One mark for insulin, one for pancreas.
Explain how the body responds when the blood glucose concentration rises after a meal. (3 marks)
Model answer
When the blood glucose rises, the pancreas releases insulin into the blood. The insulin causes the liver and muscle cells to take up glucose from the blood and store it as glycogen. This lowers the blood glucose level back to normal.
Why this scores
Three marks: pancreas releases insulin; liver/muscles take up glucose; stored as glycogen / level returns to normal.
Explain how the body responds when it becomes too cold. (4 marks)
Model answer
When the body is too cold, the muscles begin to shiver — they contract rapidly, and the respiration needed for this releases heat to warm the body. At the same time, the blood vessels supplying the skin capillaries narrow (vasoconstriction), so less blood flows near the surface of the skin and less heat is lost from the body. (The hairs may also be raised to trap an insulating layer of air.) These responses raise and conserve heat, returning the temperature to normal.
Why this scores
Four marks: shivering; muscle respiration releases heat; vasoconstriction; less blood at the surface so less heat lost.
Explain how the blood glucose concentration is controlled when it becomes too high and when it becomes too low. (5 marks)
Model answer
When the blood glucose becomes too high (for example after a meal), the pancreas releases insulin. Insulin causes the liver and muscle cells to take up glucose and store it as glycogen, so the blood glucose falls back to normal. When the blood glucose becomes too low (for example during exercise), the pancreas releases glucagon. Glucagon causes the liver to break glycogen down into glucose, which is released into the blood, so the blood glucose rises back to normal. Because each hormone produces a response that reverses the change, the blood glucose is kept steady — an example of negative feedback.
Why this scores
Five marks: high → insulin; glucose stored as glycogen by liver/muscles; low → glucagon; glycogen broken down to glucose; negative feedback / level returns to normal.
Explain how the body keeps its temperature close to 37 °C when a person is (a) too hot and (b) too cold. (6 marks)
Model answer
(a) When too hot: the rate of sweating increases, so more sweat is produced; as the water in the sweat evaporates from the skin, it takes heat away from the body, cooling it. Also, the blood vessels that supply the skin capillaries widen (vasodilation), so more blood flows near the surface of the skin and more heat is lost to the surroundings by radiation. (b) When too cold: the muscles shiver, contracting rapidly, and the extra respiration releases heat to warm the body. The blood vessels supplying the skin capillaries narrow (vasoconstriction), so less blood flows near the surface and less heat is lost. In both cases the body's responses oppose the change in temperature (negative feedback), keeping it close to the normal 37 °C.
Why this scores
Up to 6 marks: hot — more sweating, evaporation removes heat, vasodilation, more blood near surface/more heat lost; cold — shivering, respiration releases heat, vasoconstriction, less heat lost. Award the negative-feedback idea.
Definitions to memorise and the exact keywords mark schemes credit for homeostasis answers — sharpened from recent examiner reports for the 2026 0610 sitting.
The maintenance of a constant internal environment (in body fluids and cells) despite changes in the surroundings.
A control mechanism in which a change in a condition triggers a response that reverses the change, returning it to normal.
Widening of the blood vessels supplying the skin capillaries. More blood flows near the surface, so more heat is lost (a cooling response).
Narrowing of the blood vessels supplying the skin capillaries. Less blood flows near the surface, so less heat is lost (a warming response).
The storage form of glucose in the liver and muscles. Made when glucose is high (by insulin); broken back to glucose when needed (by glucagon).
The traps other students keep falling into on homeostasis questions — taken from recent Cambridge IGCSE 0610 examiner reports and mark schemes — and how to avoid them.
Why it happens
Both are 'feedback' systems.
How to avoid it
Homeostasis works by NEGATIVE feedback — the response reverses the change. Positive feedback amplifies a change and is different.
Why it happens
Shivering involves muscle movement.
How to avoid it
Shivering is rapid muscle contraction; the RESPIRATION it requires releases heat, which warms the body.
Why it happens
Diagrams can be misleading.
How to avoid it
The vessels do not move. They DILATE (widen) or CONSTRICT (narrow) to change how much blood flows near the surface.
The things students keep getting wrong in this sub-topic, answered.