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

2. 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

3. 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

4. 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

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

6. 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.

7. Source(s):
Created by Debbie Alam 2012