8 Negative feedback systems

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Negative feedback systems :

Negative feedback systems Negative feedback is a process in which a change in a variable is detected and a response occurs within the body to reverse the direction of change.

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Provide stability, they act to restore the original state. They are stimulus-response mechanisms in which the response reduces the effect of the original stimulus. (ie the response provides feedback on a negative effect on the stimulus ) Therefore negative feedback systems are ideal for maintaining homeostasis.

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The operation of negative feedback systems involves a disturbance that acts as a stimulus which, is detected by an appropriate receptor. Activation of the receptor results in a signal being sent to a control centre. This stimulates the nervous or hormonal systems, setting about a chain of events that results in a change in the animal’s physiology or behaviour.

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The response reduces the impact of the disturbance of the receptor. In the control centre information from the sensory receptor is compared to an optimal value and other information about the wellbeing of the animal, before initiating a response. The response causes fluctuations in the stimulus being monitored. (eg glucose levels can fluctuate quite widely but core temperature is monitored more precisely)

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Most biological negative feedback mechanisms operate as a proportional control system . In other words, the size of the response is proportional to the size of the stimulus. The secretion of hormones is regulated in the same way.

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