keeping the internal environment constant. Temperature, water and glucose are all controlled.

What happens when you are too hot?

You sweat more and blood vessels near the skin widen. Both increase heat loss.

Which hormone lowers blood glucose?

insulin. It makes the liver store glucose as glycogen.

What is glucose stored as in the liver?

glycogen. Glycogen can be turned back into glucose when needed.

What is vasoconstriction?

blood vessels narrowing. Less blood flows near the skin, so less heat is lost.

Homeostasis · Cambridge IGCSE Biology (9

In plain words

Whether you're in snow or a heatwave, your insides stay at about 37 °C. Your blood sugar stays steady whether you've just eaten or not. The body is constantly measuring and adjusting, like a thermostat. Keeping conditions inside steady is homeostasis.

Three things to know

Homeostasis is keeping the internal environment constant. It works by negative feedback: a change is detected, and the response reverses it.
Too hot: sweat evaporates and cools the skin, and blood vessels near the skin widen (vasodilation) so more heat is lost. Too cold: shivering releases heat, and those vessels narrow (vasoconstriction) to keep heat in.
Blood glucose: when it rises, the pancreas releases insulin, and the liver takes glucose out of the blood and stores it as glycogen. When it falls, glucagon turns glycogen back into glucose. In Type 1 diabetes the pancreas makes no insulin.

Tips and tricks

Blood vessels don't move up or down in the skin. They get wider or narrower.
Sweat cools you only when it evaporates: the heat needed to evaporate it comes from your skin.

5 questions, about 2 minutes.

It lands in your notebook with its questions as flashcards.

Homeostasis: 5 questions and answers

These are the quiz’s questions. Do the quiz first, then come back here for the ones that got you.

What is homeostasis?
- breaking down food
- keeping the internal environment constant (the answer)
- growing new cells
- fighting disease
Temperature, water and glucose are all controlled.
What happens when you are too hot?
- You shiver.
- You sweat more and blood vessels near the skin widen. (the answer)
- Blood vessels near the skin narrow.
- Hairs stand up.
Both increase heat loss.
Which hormone lowers blood glucose?
- insulin (the answer)
- glucagon
- adrenaline
- ADH
It makes the liver store glucose as glycogen.
What is glucose stored as in the liver?
- starch
- glycogen (the answer)
- fat only
- urea
Glycogen can be turned back into glucose when needed.
What is vasoconstriction?
- blood vessels widening
- blood vessels narrowing (the answer)
- sweating
- shivering
Less blood flows near the skin, so less heat is lost.

5 questions

Tap an answer and you’ll see straight away whether it’s right, and why.

Worksheet

3 questions, 8 marks. Write your answers on paper, then check them.

Homeostasis

Cambridge IGCSE Biology (9–1) 0970 · 8 marks · papermunch.org

Name ______________________________ Date ______________

State what is meant by homeostasis.[2]
Show answerHide answer
The maintenance of a constant internal environment.
I got this one
Explain two ways in which the skin helps to cool the body when it is too hot.[3]
Show answerHide answer
Sweat glands release sweat, which evaporates and takes heat from the skin. Blood vessels near the surface dilate (vasodilation), so more blood flows near the surface and more heat is lost.
I got this one
Describe how the blood glucose concentration is brought back to normal after a meal.[3]
Show answerHide answer
The rise is detected by the pancreas, which releases insulin. Insulin causes the liver (and muscles) to take up glucose and store it as glycogen, so the blood glucose concentration falls.
I got this one

Answers: Homeostasis

1. The maintenance of a constant internal environment.
2. Sweat glands release sweat, which evaporates and takes heat from the skin. Blood vessels near the surface dilate (vasodilation), so more blood flows near the surface and more heat is lost.
3. The rise is detected by the pancreas, which releases insulin. Insulin causes the liver (and muscles) to take up glucose and store it as glycogen, so the blood glucose concentration falls.