GCSE Biology: Homeostasis and the Nervous System Guide

What is homeostasis?

Homeostasis is the regulation of the internal conditions of the body, such as temperature, water levels and blood glucose, to maintain a stable environment for cells to function properly.

The nervous system

The nervous system detects stimuli through receptors, and sends electrical impulses along neurons to the central nervous system (brain and spinal cord), which coordinates a response through effectors (muscles or glands).

Reflex actions

A reflex is a rapid, automatic response to a stimulus that doesn't involve conscious thought, passing through a reflex arc rather than the brain, allowing a faster response to protect the body from harm.

Controlling blood glucose

The pancreas releases insulin to lower blood glucose (by causing cells to take up glucose) and glucagon to raise it (by releasing stored glucose from the liver), keeping levels within a healthy range.

Common mistakes

• Confusing a reflex action with a considered, conscious response.
• Mixing up insulin (lowers blood glucose) and glucagon (raises it).
• Describing a stimulus without identifying the correct receptor, coordinator and effector involved.