Negative Feedback in Living Organisms
Negative feedback is a principle which is used by the body in order to return systems to its normal level; it does this by turning the corrective measures off. Homeostasis uses the principle of negative feedback in order to maintain a constant internal environment. There are a number of different examples of negative feedback such as thermoregulation, regulation of blood glucose and the regulation of water potential. The control of the heartbeat can also use negative feedback mechanisms.
In mammals a constant body temperature is maintained using the part of the brain called the hypothalamus, this detects information from thermoreceptors about the internal and external temperatures. The changes in the internal temperature is detected by thermoreceptors which are located in the hypothalamus and detect the temperature of the blood, while there are thermoreceptors which are located in the skin which detect any changes in the external temperature. The changes which are detected by the thermoreceptors are sent as impulses along sensory neurones to the hypothalamus where corrective measures can then be put in place by sending signals to effectors. Depending on whether temperature needs to be increased or decreased to return to normal levels depends on the mechanisms which are used to do this. For example to increase the body temperature vasoconstriction is one technique which the body uses, this involves the narrowing of blood vessels retaining the body temperature. Less sweating, hairs standing up right and shivering are also used to help increase the body temperature. To decrease the body temperature vasodilatation is used, it widens the blood vessels increasing the blood flow to the surface of the skin and therefore helping to reduce body temperature. Other methods which help to decrease body temperature are swearing and hairs lying flat. All of these methods either help to increase or decrease body temperature returning to