Biology 2 Chapter 7

Biology 2 Chapter 7 - Chapter 27: Homeostasis &...

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Chapter 27: Homeostasis & Organization of the Animal Body
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Homeostasis Maintenance of a relatively constant internal environment Required for optimal cell function Changes do occur, but within narrow ranges Homeostasis = dynamic equilibrium
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Feedback Systems Mechanisms of homeostatic control are collectively known as feedback systems There are 3 parts to feedback systems Control center (with set point) Sensor Effector
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Feedback Systems There are 2 types of feedback systems Negative feedback : more common; counteracts the effects of changes in the internal environment Positive feedback : less common; reinforces changes when such reinforcement is a psychological need
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Negative Feedback Reverses the Effects of Changes In negative feedback the response to change is to counteract the change resulting in a return to the original condition “Negative” because it negates the initial change Example: home thermostat and body temperature control
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Negative feedback above set point below control center thermometer (sensor) heater (effector) heat output increases heat output decreases hypothalamus (control center) skeletal muscles (effector) heat output (shivering) increases heat output (shivering) decreases nerve endings (sensor) on off signal (temperature) to control center signal to turn on effector signal to turn off effector nerve signal (temperature) to control center nerve signal to turn off effector nerve signal to turn on effector
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Negative Feedback Reverses the Effects of Changes Negative feedback maintains body temperature through the set point in the control system found in the hypothalamus When body temperature drops, various effector mechanisms raise it Shivering, blood vessel constriction, metabolic rate rise
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This note was uploaded on 10/10/2011 for the course BIOL 1002 taught by Professor Pomarico during the Fall '08 term at LSU.

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Biology 2 Chapter 7 - Chapter 27: Homeostasis &...

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