A student is investigating how the body maintains a stable internal environment. Explain how the nervous system and the hormonal system work together to maintain homeostasis, including what is meant by a negative feedback mechanism.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
The human body constantly monitors and adjusts its internal conditions, such as blood glucose concentration and core body temperature, to keep them within narrow limits. This process is called homeostasis.
Model answer (5 marks)
Homeostasis is the maintenance of a stable internal environment.
1. Receptors detect a change in an internal condition.
2. A coordination centre (e.g. the brain or pancreas) processes the information.
3. The centre sends a signal via the nervous system (nerve impulses) or the hormonal system (hormones in the blood) to effectors.
4. Effectors (muscles or glands) act to counteract the change.
5. Negative feedback is the process by which the response reduces or reverses the original change, bringing the condition back to the set point.
1. Receptors detect a change in an internal condition.
2. A coordination centre (e.g. the brain or pancreas) processes the information.
3. The centre sends a signal via the nervous system (nerve impulses) or the hormonal system (hormones in the blood) to effectors.
4. Effectors (muscles or glands) act to counteract the change.
5. Negative feedback is the process by which the response reduces or reverses the original change, bringing the condition back to the set point.
Examiner tips
- Use the exact sequence: receptors → coordination centre → signal → effectors → response.
- Show that the response opposes the initial change – key to negative feedback.
- Mention both nervous and hormonal pathways as examples.
- Keep each point brief but complete.
Mark scheme (5 marks)
- Homeostasis is the maintenance of a stable internal environment / keeping internal conditions within narrow limits
- Receptors detect a change / stimulus in internal conditions
- A coordination centre (e.g. the brain or pancreas) processes the information and sends a signal via the nervous system (nerve impulses) or hormonal system (hormones in the blood) to effectors
- Effectors (muscles or glands) bring about a response to counteract / reverse the change
- Negative feedback is the process by which the response reverses / reduces the original change, returning conditions back to the set point / normal level
Key terms in this question
homeostasis · negative feedback
Related
- All OCR A-Level Biology B — Advancing Biology (H422) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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