Balances and Glassware for Solution Preparation
Homeostasis: Regulating the Internal Environment
Homeostasis means "steady state," or internal balance, and is a recurrent theme in understanding how organisms function as a whole. A stable environment, maintained within narrow limits, is essential to all life.
Organisms constantly exchange energy and materials with their environments. The gains and losses must balance over some type of time interval. For example, as glucose enters the blood after a meal, excess glucose is transported to the liver to be converted to glycogen. Between meals, as glucose levels drop, the liver converts glycogen back to glucose and releases it into the bloodstream.
Homeostatic control systems have a receptor that detects change, along with a control center that directs the response to an effector. The body monitors internal conditions and makes corrections through biofeedback loops. In negative feedback loops, a change in the monitored variable triggers a response to counteract further change in the same direction. If excess heat is detected in the body, the brain signals the blood vessels near the surface of the body to dilate and the sweat glands to increase production. As body temperature nears normal, the brain reverses the process by slowing sweat production and constricting blood vessels.
In positive feedback loops, a change in the monitored variable triggers further action rather than reversing the action. A common example of a positive feedback loops occurs in blood clotting, with each clotting reaction activating another until the bleeding is stopped.
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