Homeostasis

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The principles of homeostasis

Receptors and effectors

Its impossible to maintain a living mammal in a completely stable state because everything causes minute changes, instead the body maintains a dynamic equilibrium with small fluctuations over a narrow range of conditions (homeostasis)

Receptors and effectors are vital for the body to maintain this dynamic equilibrium, sensory receptors detect changes in the internal and external environments of an organism

Homeostasis monitors changes in the internal environment e.g. the pH of the blood, core body temperature and concentrations of urea and sodium ions in the blood

Information from the sensory receptors is transmitted to the brain and impulses are sent along the motor neurones to the effectors to bring about changes to restore the equilibrium in the body, effectors are muscles or glands that react to the motor stimulus to bring about a change in response to a stimulus and both are vital in a homeostatic system

Feedback systems

Homeostasis depends on sensory receptors detecting small changes in the body, and effectors working to restore the 'status quo'

These precise control mechanisms in the body are based on feedback systems that enable the maintenance of a relatively steady state around a narrow range of conditions

Negative feedback systems

Most of the feedback systems in the body involve negative feedback. A small change in one direction is detected by sensory receptors, as a result, effectors work to reverse the change and restore conditions to their base level. Negative feedback systems work to reverse the initial stimulus

Positive feedback systems

In a positive feedback system a change in the internal environment of the body is detected by sensory receptors and effectors are stimulated to reinforce that change and increase the response

Thermoregulation in ectotherms