homeostasis

Temperature regulation is an examples of negativefeedback mechanism. The optimal body core temperature is about 36.8 ºC which is the homeostatic set point. This optimal temperature is closelyregulated due to factors like enzymes works best at certain temperatures.

Ifthe temperature raises to 43ºC, itmay be fatal and cause death.  Whereas, ifthe temperature falls below 32ºC, theindividual may go into coma and die. The changes in the temperature aredetected by nerve-endings in the skin and the hypothalamus of the brain. Whenblood temperature raises above the optimal temperature, the heat-loss centre inthe hypothalamus is activated which then initiates an autonomic response. Thisresponse triggers changes to the effectors like the blood vessels whichvasodilate and increase blood flow to the skin so that there is increase inradiation, conduction and convection to lose heat. Subsequently, metabolic rateand muscular activity are decreased to slow down further heat production.

Thesweat glands, additional effectors, are activatIn negative feedback loop, has acounteraction effect on its own influence. Therefore, the negative feedbackmechanism can increase or decrease the stimulus. If the level is high, the bodydecreases it and if it is too low, it elevates it and thus it is known asnegative feedback. Homeostasis always tends to provide optimal internalenvironment in which the body can function best.

Another positive feedback mechanism is bloodclotting. When a blood vessel is damaged, platelets arrive to the site andstick to the site of the injury. They release chemical signals that attractmore platelets to the site and accelerate the process of clotting.

Thiscontinues until the clot repairs the damaged vessel.During labor, the oxytocin hormone isreleased by the hypothalamus and released by posterior pituitary. The oxytocinstimulates and intensifies the contraction of the uterus, forcing the head ofthe baby into the cervix. Subsequently, more oxytocin is release when stretchreceptors that are in the cervix are activated. In turn, more oxytocin isreleased causing more contractions and maintaining labor. This cycle continuesuntil the baby is born.

Once the baby is born, the stretch receptors aredeactivated and since the stimulus is not present anymore, the release ofoxytocin is stopped ending the positive feedback mechanism.In positive feedback mechanism, the output isamplified to maintain homeostasis. They are designed to push levels out ofnormal ranges.

This is achieved by initiating a series of events, whichoriginates to amplify the effect of the stimulus. This mechanism can be usefulbut are rarely used due to its ability to become uncontrollable. For instance,child birth and blood clotting are paramount examples of the use of positivefeedback mechanism.

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