GCSE Biology - Homeostasis

Summary: Homeostasis

Homeostasis is the regulation of conditions inside the body to maintain a stable internal environment, even when conditions inside or outside the body change. Cells need suitable conditions to function—for example, an appropriate temperature and pH, and enough glucose and water. These conditions may fluctuate but generally remain within narrow limits.

The body uses automatic control systems to detect changes from the preferred range and trigger responses that counteract them.

Components of an Automatic Control System

1. Receptors detect a change, such as a rise or fall in temperature.
2. Coordination centres, such as the brain or spinal cord, interpret the information and determine a response.
3. Effectors carry out the response. These are usually muscles, which contract, or glands, which release hormones.

How Signals Are Sent

• The nervous system uses electrical impulses that travel quickly and precisely through nerves, allowing rapid responses.
• The endocrine system uses hormones released into the bloodstream. Hormones affect only cells with the appropriate receptors. Endocrine responses are generally slower, longer-lasting, and more widespread than nervous responses.

Negative Feedback

Negative feedback reverses a change and helps return a condition to its normal level. If a level becomes too low, the body responds to raise it; if it becomes too high, a response lowers it.

Example: Temperature Regulation

• If a person becomes too cold, receptors detect the low temperature and send information to coordination centres. Signals then prompt effectors, such as muscles, to cause shivering, which raises body temperature.
• If the person becomes too hot, a different response—such as sweating—helps lower body temperature.
• If the temperature moves too far in either direction, the relevant response is triggered again, keeping it within a suitable range.

Speakers or Sources Featured

• Narrator: One unnamed narrator presenting the lesson on the Cognito channel.