GCSE Biology - Homeostasis | Receptors, Coordination Centres, Effectors | Negative Feedback

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, including an appropriate temperature and pH, and enough glucose and water. These conditions are kept within small ranges rather than held perfectly constant.

Automatic control systems

The body uses automatic control systems to detect changes from preferred levels and trigger responses that bring conditions back toward normal. These systems involve:

• Receptors detect changes, such as a rise or fall in temperature.
• Coordination centres, such as the brain or spinal cord, interpret the information and determine a response.
• Effectors carry out the response. These are generally muscles, which may contract, or glands, which may release hormones.

Because these components can be in different parts of the body, signals connect them:

• The nervous system sends fast, precise electrical impulses through nerves, enabling rapid responses.
• The endocrine system releases hormones into the bloodstream. Hormones travel around the body but affect only cells with the appropriate receptors. This system is generally slower, longer-lasting, and more widespread than the nervous system.

Negative feedback

Negative feedback reverses a change that has moved a condition away from its normal level:

• If a level becomes too high, the response lowers it.
• If a level becomes too low, the response raises it.

The process continues as needed, helping keep conditions within their normal range.

Example: Body temperature regulation

1. If the body becomes too cold: Receptors detect the lower temperature and send information to coordination centres. Signals then prompt effectors, such as muscles, to cause shivering. Shivering helps raise body temperature toward normal.
2. If the body becomes too hot: Receptors detect the rise in temperature. The resulting signals prompt responses such as sweating, which helps lower temperature toward normal.
3. If temperature moves too far in the opposite direction, the control process responds again, creating a regulatory loop.

Speakers and sources

• Speaker: A single narrator presenting the biology lesson.
• Source/channel: Cognito.