AQA · GCSE · Combined Science
Course version: 8464 · Version from Sept 2018
Students should be able to explain that homeostasis is the regulation of…
Full specification wording
Homeostasis: Students should be able to explain that homeostasis is the regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes.
Homeostasis keeps the internal conditions of a cell or organism within narrow limits so that functions such as enzyme activity continue at an optimum rate.
Checked against the AQA 8464 specification (opens in a new tab) on .
- Point 1 of 11
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Homeostasis keeps the internal conditions of a cell or organism within narrow limits so that functions such as enzyme activity continue at an optimum rate. Internal changes include temperature, blood glucose concentration and water content; external changes include air temperature, exercise and diet. Receptors detect a change (stimulus), a coordination centre processes the information, and effectors (muscles or glands) bring about a response that reverses the change. For example, when body temperature rises during exercise, thermoreceptors detect it, the brain coordinates a response, and sweat glands and skin blood vessels cool the body. This negative feedback restores optimum conditions.
What earns the marks
- Homeostasis is the regulation of internal conditions within narrow limits, not a fixed unchanging state.
- Receptors detect stimuli, coordination centres process information, and effectors produce responses.
- Negative feedback reverses the detected change to restore optimum conditions.
Common mistakes and how to put them right
Saying homeostasis keeps conditions completely constant.
Put it right: It keeps conditions within narrow limits around an optimum, so small fluctuations occur.
Confusing effectors with receptors.
Put it right: Receptors detect the stimulus, while effectors such as muscles or glands carry out the response.
Describing positive feedback as the main mechanism.
Put it right: Most homeostatic control uses negative feedback, which reverses the change.
Exam tips
- Use the sequence stimulus → receptor → coordination centre → effector → response when explaining a homeostatic example.
- Name one internal change and one external change, then state the response that reverses each.
- Link the explanation to optimum conditions for enzyme action rather than saying only that the body stays the same.
Try the lesson
The start of the Homeostasis: Students should be able to explain that homeostasis is the regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes. lesson, made from checked teaching notes for this specification point.
Have a go first
What name is given to the regulation of the internal conditions of an organism to maintain optimum conditions for function?
Listen
Homeostasis keeps the internal conditions of a cell or organism within narrow limits so that functions such as enzyme activity continue at an optimum rate. Internal changes include temperature, blood glucose concentration and water content; external changes include air temperature, exercise and diet. Receptors detect a change (stimulus), a coordination centre processes the information, and effectors (muscles or glands) bring about a response that reverses the change. For example, when body temperature rises during exercise, thermoreceptors detect it, the brain coordinates a response, and sweat glands and skin blood vessels cool the body. This negative feedback restores optimum conditions. A strong answer earns marks for these points. Homeostasis is the regulation of internal conditions within narrow limits, not a fixed unchanging state. Receptors detect stimuli, coordination centres process information, and effectors produce responses. Negative feedback reverses the detected change to restore optimum conditions. A common slip: Saying homeostasis keeps conditions completely constant. Instead, it keeps conditions within narrow limits around an optimum, so small fluctuations occur. Exam tip: Use the sequence stimulus → receptor → coordination centre → effector → response when explaining a homeostatic example.
Key words
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Negative feedback
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Receptors, coordination centres and effectors
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Response to internal and external change
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Regulation of internal conditions
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See every definition
- Negative feedback
- A response that reverses the detected change to restore optimum conditions.
- Receptors, coordination centres and effectors
- Receptors detect stimuli, coordination centres process information, and effectors produce responses.
- Response to internal and external change
- Operating in response to internal changes, such as blood glucose concentration, and external changes, such as air temperature.
- Regulation of internal conditions
- Keeping the internal conditions of a cell or organism within narrow limits to maintain optimum conditions for function.
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