Pearson Edexcel · GCSE · Biology
Course version: 1BI0 · Version from Sept 2016
Explain the importance of maintaining a constant internal environment in…
Full specification wording
Topic 7 – Animal coordination, control and homeostasis: 7.9 Explain the importance of maintaining a constant internal environment in response to internal and external change
Homeostasis keeps conditions inside the body, such as temperature, blood glucose concentration and water content, within narrow limits even when the internal or external environment changes.
Checked against the Pearson Edexcel 1BI0 specification (opens in a new tab) on .
- Point 8 of 19
Study notes
From the checked teaching notes for this specification point.
The idea
Homeostasis keeps conditions inside the body, such as temperature, blood glucose concentration and water content, within narrow limits even when the internal or external environment changes. This matters because enzymes and cells work best at particular temperatures and pH; too high a temperature denatures enzymes, while too low slows metabolism. Cells also need a steady supply of glucose and the right water balance so they neither swell nor shrink. Control systems detect change, and effectors such as muscles or glands respond to restore the set point.
For example: Sweating and vasodilation cool the body when it overheats, while shivering and vasoconstriction conserve heat when it is cold.
What earns the marks
- Homeostasis keeps internal conditions such as temperature, blood glucose and water content within narrow limits.
- Enzymes and cells function best at particular temperatures and pH, so deviations reduce metabolic rate or denature enzymes.
- Control systems detect internal and external change and effectors respond to restore the set point.
- Examples include sweating and vasodilation to cool the body, and shivering and vasoconstriction to conserve heat.
- Maintaining stable water and glucose levels prevents cells from being damaged and keeps them supplied with energy.
Common mistakes and how to put them right
Thinking homeostasis means conditions never change.
Put it right: Conditions fluctuate but are kept within narrow limits around a set point.
Believing body temperature is kept perfectly constant.
Put it right: It is regulated within a narrow range, not fixed exactly.
Assuming only external change matters.
Put it right: Internal changes such as blood glucose after a meal are also corrected.
Exam tips
- Name the specific condition being controlled and the effect of it drifting too high or too low.
- Link each response to the effector that carries it out, such as sweat glands or muscles in blood vessel walls.
- Use the idea of a set point and negative feedback to explain how change is reversed.
Try the lesson
The start of the Topic 7 – Animal coordination, control and homeostasis: 7.9 Explain the importance of maintaining a constant internal environment in response to internal and external change lesson, made from checked teaching notes for this specification point.
Have a go first
Which term describes the maintenance of a steady internal environment such as constant body temperature and blood glucose?
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