Principles of Homeostasis Notes

AQA GCSE Biology: Revision notes

Key facts

Homeostasis is regulating internal conditions to keep them at the optimum for function.
It matters because enzymes and cells only work well in a narrow range of conditions.
The body controls blood glucose, body temperature and water levels.
Responses can be nervous (fast) or hormonal (slower, longer-lasting).
Every control system has receptors, coordination centres and effectors.

The pathway in every control system

Homeostasis keeps internal conditions at their optimum, whatever changes inside or outside the body.

Homeostasis is the regulation of the internal conditions of a cell or organism.

Enzymes and other cell processes work efficiently only within a narrow range. Outside it, reactions slow down or enzymes may denature.

The body controls blood glucose concentration, body temperature and water levels.

Then back to step 1

A control system restores the optimum

Why is homeostasis important?

A response can be nervous (fast, electrical) or chemical (slower, but longer-lasting).

Both kinds of response can control a condition.

Nervous responses use electrical impulses and are fast.
Hormonal (chemical) responses use hormones in the blood and are slower but last longer.

Nervous

Hormonal

Which response is slower but longer-lasting?

Receptors detect stimuli, coordination centres process the information and effectors produce the response.

Every system has the same three parts.

Receptors detect stimuli.
Coordination centres such as the brain, spinal cord and pancreas receive and process information.
Effectors are muscles or glands that bring about a response.

In any example (glucose, temperature, water) identify the receptor, coordination centre and effector.

Information flow in a control system

Which part of a control system is a muscle or gland?

Describe the three components of a control system in the body.

[3 marks]

That's the notes covered.

Carry on to the next subtopic.