AQA GCSE Biology (8461), Higher tier · Homeostasis and response
Practise Homeostasis. 11 exam-style questions on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
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Homeostasis maintains the optimum conditions for the molecules that control reactions in cells. Name these molecules.
Enzymes
All the automatic control systems in the body include receptors, coordination centres and effectors. Give the two types of effector.
Muscles and glands
These steps happen in one automatic control system in the body.
Body temperature increases.
Temperature receptors in the skin detect the change.
Nerve impulses travel to the brain.
The brain sends nerve impulses to the sweat glands.
The sweat glands produce more sweat.
Body temperature decreases.
Name the coordination centre.
The brain
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy6 marks
Homeostasis is important for the human body to work properly.
(a) What is meant by homeostasis?[2]
(b) Which three of these are controlled by homeostasis in the human body? Tick (✓) three boxes.[3]
Blood glucose concentration
Body temperature
Eye colour
Height
Water levels
(c) Homeostasis maintains the optimum conditions for the molecules that control reactions in cells. Name these molecules.[1]
Show the answer and mark scheme
(a)
the regulation of the internal conditions (of a cell or organism)
to maintain optimum conditions for function (in response to internal and external changes)
(b)Answer: Blood glucose concentration; Body temperature; Water levels
(c)Answer: Enzymes
enzymes
Question 2Medium7 marks
These steps happen in one automatic control system in the body.
Body temperature increases.
Temperature receptors in the skin detect the change.
Nerve impulses travel to the brain.
The brain sends nerve impulses to the sweat glands.
The sweat glands produce more sweat.
Body temperature decreases.
(a) Name the receptors in this control system.[1]
(b) Name the coordination centre.[1]
(c) Name the effectors.[1]
(d) Is this a nervous response or a chemical response? Give a reason for your answer.[2]
(e) Explain why step 6 is important.[2]
Show the answer and mark scheme
(a)
temperature receptors (in the skin)
(b)Answer: The brain
brain
(c)Answer: Sweat glands
sweat glands
(d)
nervous
it uses nerve impulses / neurones (not hormones)
(e)
it returns body temperature to the optimum
(so) enzymes work at their optimum rate / are not denatured
Question 3Hard9 marks
The concentration of carbon dioxide in the blood is controlled automatically. When the concentration rises, receptors in the walls of some arteries detect the change and send impulses to the medulla in the brain. The medulla then sends impulses to the diaphragm and the muscles between the ribs, which contract faster and more strongly.
(a) Identify the receptors, the coordination centre and the effectors in this control system.[3]
(b) Explain how this control system returns the concentration of carbon dioxide in the blood to normal.[2]
(c) Suggest why the concentration of carbon dioxide in the blood rises during exercise.[2]
(d) A person holds their breath for 30 seconds. Predict and explain what happens to the concentration of carbon dioxide in their blood and to their breathing.[2]
Show the answer and mark scheme
(a)
receptors: (receptors in) the walls of the arteries
coordination centre: the medulla / brain
effectors: the diaphragm and the muscles between the ribs
(b)
the breathing rate / depth of breathing increases
(so) more carbon dioxide is removed from the blood and breathed out
(c)
the muscles respire faster (to transfer more energy)
(so) more carbon dioxide is produced (and diffuses into the blood)
(d)
the concentration of carbon dioxide rises (because it is not breathed out)
receptors detect the rise and the medulla causes a strong urge to breathe / faster, deeper breathing when breathing starts again
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