on this cheat sheet
Everything on the GCSE Biology Homeostasis poster is written out below, section by section. Use it to search the sheet, copy parts into your own notes, or check a fact quickly.
What is homeostasis?
Homeostasis is the regulation of the body's internal conditions. It keeps internal conditions within narrow limits even when the outside world changes, and keeps cells - and the enzymes inside them - working properly.
The negative feedback loop
Every homeostatic system works the same way:
Receptor → Coordination centre → Effectors → Response
- Receptors detect a change in the internal environment.
- The coordination centre (brain, spinal cord or a gland) processes the information and decides what to do.
- Effectors (muscles or glands) carry out the response that brings the level back to normal.
- The level returns to the set-point and receptors stop firing.
This is called negative feedback: whenever a variable drifts away from its set-point, the body acts to push it back.
What gets controlled?
Body temperature
- Receptor: skin and hypothalamus
- Coordination centre: hypothalamus (brain)
- Effectors: skin, muscles, sweat glands
Blood glucose
- Receptor: pancreas
- Coordination centre: pancreas
- Effectors: liver, muscle cells
Water balance
- Receptor: hypothalamus
- Coordination centre: pituitary
- Effectors: kidneys
Variables stay near their set-point
Internal variables don't stay exactly the same - they gently oscillate around a set-point and are kept within narrow limits.