Why is "Describing homeostasis as positive feedback." a common mistake in Homeostasis?

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 is "Saying shivering warms the body 'just by movement'." a common mistake in Homeostasis?

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 is "Saying the skin blood vessels 'move' towards or away from the surface." a common mistake in Homeostasis?

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.

Coordination and ResponseCambridge IGCSE Biology 0610 Extended

Homeostasis

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Homeostasis — Cambridge IGCSE 0610 Biology Extended (2026)

Keeping inside steady. Blood glucose, body temperature, water — all controlled by NEGATIVE FEEDBACK.

What you’ll learn

Mapped to the Cambridge IGCSE 0610 syllabus (2026-2028).

14.4 — Define homeostasis.
14.4 — Describe blood glucose regulation by insulin and glucagon.
14.4 — Describe how body temperature is maintained.
14.4 — Outline negative feedback.

What is homeostasis?

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?

BLOOD GLUCOSE (~90 mg/100 mL).
BODY TEMPERATURE (~37°C).
WATER + ION balance.
pH (~7.4 in blood).
CO₂ levels.
Many others.

Why it matters. Cells (especially enzymes) work in a NARROW range of conditions:

Outside ~37°C → enzymes work badly or denature.
pH outside ~7.4 → enzymes denature.
Wrong glucose → cells can't respire properly.
Without homeostasis, cells fail → organism fails.

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.

In negative feedback the effector's response reverses the change, returning conditions to the set point.

The four parts of any feedback loop:

Variable — what's being controlled (e.g. blood glucose).
Receptor — detects the level (e.g. cells in pancreas).
Control centre — decides response (e.g. pancreas, hypothalamus).
Effector — carries out response (e.g. liver cells, sweat glands).

Worked qualitative. Why is normal body temperature ~37°C, not, say, 25°C or 50°C?

Enzymes EVOLVED in a 37°C environment (mammals warm-blooded for ~200 million years).
They work optimally there.
Hotter would risk denaturation; colder would slow reactions.
Warm-blooded animals trade extra energy demand (must eat more to make heat) for the benefit of constant enzyme activity.

Cambridge tip. Always mention NEGATIVE FEEDBACK. Cambridge marks the term.

Constant internal environment.
Glucose, temperature, water, pH.
Negative feedback mechanism.
Receptor → control → effector.

Blood glucose regulation

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.

Pancreas detects HIGH blood glucose.
Releases INSULIN.
Insulin tells:
- LIVER to take up glucose, store as GLYCOGEN.
- MUSCLES to take up glucose, store as glycogen.
- Body cells to take up more glucose for respiration.
Blood glucose FALLS back to ~90 mg/100 mL.

Between meals / during exercise — glucose falls.

Pancreas detects LOW blood glucose.
Releases GLUCAGON.
Glucagon tells:
- LIVER to break down glycogen → release glucose into blood.
Blood glucose RISES back to ~90 mg/100 mL.

Insulin and glucagon are antagonistic — one lowers glucose, the other raises it, back to normal.

Diabetes.

Type 1 diabetes:

Body's immune system damages pancreatic cells → no insulin made.
Glucose stays high after eating; can't enter cells.
Symptoms: high blood glucose, glucose in urine, thirst, weight loss, tiredness.
Treatment: insulin injections matched to meals.

Type 2 diabetes:

Cells become RESISTANT to insulin (insulin made, but cells don't respond).
Risk factors: obesity, genetics, lack of exercise.
Treatment: diet, exercise, drugs that improve insulin sensitivity.

Worked qualitative. Why is glucose in urine a sign of diabetes?

Healthy kidney reabsorbs ALL glucose.
In diabetes, blood glucose so high that kidney reabsorption is overwhelmed → glucose 'spills' into urine.
Also draws water with it (osmotic effect) → more frequent urination + thirst.
Used as one of the key diagnostic tests.

Cambridge tip. Memorise BOTH insulin AND glucagon. Cambridge often gives a graph and asks you to explain its dips and peaks.

Insulin: high glucose → store as glycogen.
Glucagon: low glucose → break glycogen.
Both from pancreas.
Diabetes type 1: no insulin.
Diabetes type 2: cells resist insulin.

Body temperature regulation

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.

Sweat glands secrete water (with some salts).
Water EVAPORATES from skin surface.
Evaporation absorbs HEAT (high latent heat of vaporisation) → cools the body.

2. Vasodilation.

Skin blood vessels WIDEN.
More blood flows near surface.
Heat radiates from blood out to surroundings.
Skin appears flushed/red.

3. Hair lying flat.

Hair erector muscles RELAX.
Hairs lie down.
Trap less air → less insulation → faster heat loss.

4. Behavioural responses.

Move to shade.
Reduce activity.
Drink water.

When too COLD — body warms by:

1. Shivering.

Muscles contract rapidly.
Each contraction = respiration → releases HEAT.
Body warms (although exhausting and uses energy).

2. Vasoconstriction.

Skin blood vessels NARROW.
Less blood near surface.
Heat retained in core.
Skin looks pale/blue (extreme).

3. Hair standing up.

Hair erector muscles CONTRACT.
Hairs stand up.
Trap air close to skin → insulation.
(Humans only get 'goosebumps' — vestigial response from when we had more body hair.)

4. Behavioural responses.

Curl up (reduces surface area).
Move into the sun / put on layers / increase activity.

Skin = the main thermoregulatory organ. Sensors in skin AND brain detect temperature. Hypothalamus (in the brain) coordinates the response.

Opposite responses for hot and cold both return core temperature to 37°C.

Worked qualitative. Why does drinking ice water 'cool you down' less than you might expect?

Body has to warm the cold water back up to 37°C.
Some heat is absorbed → minor cooling effect.
But EVAPORATION from skin (sweating) is far more efficient because of water's high latent heat.
A drop of sweat carries away ~2,400 J of heat per gram evaporated.

Cambridge tip. Always pair the response with the MECHANISM — not just 'sweat = cooling' but 'sweat evaporates → takes heat away'.

Hot: sweat + vasodilation + flat hair.
Cold: shiver + vasoconstriction + raised hair.
Skin senses + hypothalamus coordinates.
Behavioural responses too.

How it’s examined

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.

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Step-by-step worked examples — Homeostasis

Step-by-step solutions to past-paper-style questions on homeostasis, written exactly the way a tutor would explain them at the board.

1Define homeostasis
Getting started• definition
Question
Define homeostasis and give two examples of conditions that are kept constant.
Step-by-step solution
1. Step 1
  Homeostasis is the maintenance of a constant internal environment, despite changes in the surroundings.
2. Step 2
  Example 1: the blood glucose concentration is kept constant.
3. 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.
2What homeostasis controls
Getting started• examples, identify
Question
Name the hormone responsible for each: (a) lowering blood glucose; (b) raising blood glucose. State which gland produces them.
Step-by-step solution
1. Step 1
  (a) Lowering blood glucose → insulin, from the pancreas.
2. 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.
3Blood glucose regulation
Building confidence• Adapted from 0610/42 Oct/Nov 2024 Q13• blood glucose
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
1. Step 1
  After a meal (glucose rises): the pancreas releases insulin.
2. 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.
3. Step 3
  During exercise (glucose falls): the pancreas releases glucagon.
4. 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.
4Body temperature control
Building confidence• thermoregulation
Question
Describe how the body responds when it is (a) too hot and (b) too cold.
Step-by-step solution
1. Step 1
  (a) Too hot: sweating increases — water in sweat evaporates from the skin, taking heat away.
2. Step 2
  The blood vessels supplying the skin capillaries widen (vasodilation), so more blood flows near the surface and more heat is lost.
3. Step 3
  (b) Too cold: shivering occurs — the muscles contract rapidly, and the respiration this needs releases heat.
4. 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.
5Negative feedback
Stretch• negative feedback
Question
Explain what is meant by negative feedback, using the control of body temperature as an example.
Step-by-step solution
1. 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.
2. 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.
3. Step 3
  If the body becomes too cold, responses such as shivering and vasoconstriction are triggered to warm the body up.
4. 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.
6Type 1 diabetes
Stretch• Syllabus 14.4• diabetes
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
1. Step 1
  Without enough insulin, the body cannot lower the blood glucose after a meal.
2. Step 2
  So the blood glucose concentration rises too high, and glucose may appear in the urine.
3. Step 3
  A high blood glucose level is harmful, and the person may feel tired or thirsty.
4. 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.

Model Answers — Homeostasis

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.

Question 1
Paper 4 short-answer style1 mark
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'.
Question 2
Paper 4 short-answer style2 marks
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.
Question 3
Paper 4 structured style3 marks
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.
Question 4
Paper 4 (Extended) structured style4 marks
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.
Question 5
Paper 4 (Extended) structured style5 marks
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.
Question 6
Paper 4 (Extended) extended-response style6 marks
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.

Key Definitions and Keywords — Homeostasis

Definitions to memorise and the exact keywords mark schemes credit for homeostasis answers — sharpened from recent examiner reports for the 2026 0610 sitting.

Homeostasis
Examiner keyword
The maintenance of a constant internal environment (in body fluids and cells) despite changes in the surroundings.
Negative feedback
Examiner keyword
A control mechanism in which a change in a condition triggers a response that reverses the change, returning it to normal.
Vasodilation
Widening of the blood vessels supplying the skin capillaries. More blood flows near the surface, so more heat is lost (a cooling response).
Vasoconstriction
Narrowing of the blood vessels supplying the skin capillaries. Less blood flows near the surface, so less heat is lost (a warming response).
Glycogen
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).

Common Mistakes and Misconceptions — Homeostasis

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.

✕Describing homeostasis as positive feedback.
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.
✕Saying shivering warms the body 'just by movement'.
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.
✕Saying the skin blood vessels 'move' towards or away from the surface.
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.

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Homeostasis

Short Study Notes in the form of Slides

Short Study Notes — Homeostasis

Detailed Notes

What you’ll learn

How it’s examined

1Define homeostasis

2What homeostasis controls

3Blood glucose regulation

4Body temperature control

5Negative feedback

6Type 1 diabetes

Homeostasis

Negative feedback

Vasodilation

Vasoconstriction

Glycogen

✕Describing homeostasis as positive feedback.

✕Saying shivering warms the body 'just by movement'.

✕Saying the skin blood vessels 'move' towards or away from the surface.

Practice questions

Past paper style quiz

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Video lesson