FEEDBACK MECHANISMS & HOMEOSTASIS HOMEOSTASIS Maintaining the internal environment within a stable range given factors that influence the external environment Homeostasis controls many aspects of the internal environment, for example: Body temperature Blood concentrations of: glucose, hormones, carbon dioxide and ions Oxygen levels Blood pH Blood pressure Solute concentration (Water balance) FEEDBACK MECHANISMS Maintain homeostasis by detecting and responding to a stimulus A non-biology example: NEGATIVE FEEDBACK Reduces the size of the stimulus to restore homeostasis Temperature regulation Blood glucose Blood pressure Stimulus effector response NEGATIVE FEEDBACK: HUMANS Protein receptor on cells surface takes up insulin BLOOD PRESSURE NEGATIVE FEEDBACK A. stimulus exercise increases blood pressure B. receptor gets the message to the (C) control center. D. The effector, the heart, pumps blood slower & E. blood vessels dilate & get wider to allow blood to pass through). F. Homeostasis is obtained NEGATIVE FEEDBACK: PLANTS POSITIVE FEEDBACK - CHILDBIRTH POSITIVE FEEDBACK Response increases the original stimulus to restore homeostasis Rarely used Only normal when there is a definite end point Childbirth Blood clotting