Homeostasis: Positive/ Negative Feedback Mechanisms When the brain’s temperature regulation center receives data from the sensors indicating that the body’s temperature exceeds its normal range, it stimulates a cluster of brain cells referred to as the “heat-loss center.” This st Humans have a similar temperature regulation feedback system that works by promoting either heat loss or heat gain (b). This prevents blood sugar levels from continuing to drop below the normal range. As glucose concentration in the bloodstream drops, the decrease in concentration-the actual negative feedback-is detected by pancreatic alpha cells, and insulin release stops. The insulin signals skeletal muscle fibers, fat cells (adipocytes), and liver cells to take up the excess glucose, removing it from the bloodstream. These pancreatic beta cells respond to the increased level of blood glucose by releasing the hormone insulin into the bloodstream. For example, in the control of blood glucose, specific endocrine cells in the pancreas detect excess glucose (the stimulus) in the bloodstream. This stimulus is “heard” by a specific sensor. In order to set the system in motion, a stimulus must drive a physiological parameter beyond its normal range (that is, beyond homeostasis). An effector is the component in a feedback system that causes a change to reverse the situation and return the value to the normal range. If the value deviates too much from the set point, then the control center activates an effector. The control center is the component in a feedback system that compares the value to the normal range. This value is reported to the control center. A sensor, also referred to a receptor, is a component of a feedback system that monitors a physiological value. A negative feedback system has three basic components (a).
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