Homeostasis

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• Homeostasis

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• A dynamic state of equilibrium, or balance, in
  which internal conditions vary, but always within
  relatively narrow limits.

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Homeostasis

• Values of variables fluctuate around the set
  point to establish a normal range of values.
• Set point the ideal normal value of a
• variable.
• What is the set point for body temperature?

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Feedback Systems

• Two types negative and positive
• Components
• Receptor monitors the value of some variable
• Control center establishes the set point
• Effector can change the value of the variable
• Stimulus deviation from the set point detected
  by the receptor
• Response produced by the effector

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Negative Feedback

• Any deviation from the set point is made smaller
  (resisted)
• Examples regulation of blood pressure, body
  temperature, blood sugar levels

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Example of Negative Feedback
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Positive Feedback

• When a deviation occurs, the response is to make
  the deviation greater
• Unusual in normal, healthy individuals, leads
  away from homeostasis and can result in death
• Example of normal positive feedback childbirth
• Example of harmful positive feedback after
  hemorrhage, blood pressure drops and the hearts
  ability to pump blood decreases