Homeostatic Mechanisms Processes that keep the body’s environment stable .

Processes that keep the body‘s environment stable sometimes work in opposition to one another Thyroid gland produces hormone Normal Calcium level Parathyroid gland produces hormone Normal Calcium Level calcitonin RISE DROP DROP RISE parathormone

Processes that keep the body‘s environment stable sometimes work in opposition to one another Thyroid gland produces hormone Normal Calcium level Parathyroid gland produces hormone Normal Calcium Level calcitonin RISE DROP DROP RISE parathormone

A feedback system is one in which the response alters the stimulus Stimulus - increased C02 in Blood Receptor Nervous transmission Effectors – muscles in diaphragm Response increased breathing rate Alteration to original stimulus – decreased C02

Feedback systems are usually negative – they will remove or inhibit the stimulus. A positive feedback system would increase the stimulus

Another positive feedback mechanism: During exercise, one example of positive feedback is calcium-induced calcium release in cardiac muscle cells that occurs with each heartbeat. Depolarization of the cardiac muscle plasma membrane leads to a small influx of calcium through membrane calcium channels. This leads to an explosive release of calcium from the intracellular organelles, a rapid increase in the cytosolic calcium level, and activation of the contractile machinery. Positive feedback, if unchecked, can lead to a vicious cycle and dangerous situations.

Source(s): www.answers.com/topic/positive-feedback http://en.wikipedia.org/wiki/Feedback http://www.answers.com/homeostasis Created by Debbie Alam 2012