FEEDBACK MECHANISMS HOMEOSTASIS HOMEOSTASIS Maintaining the internal environment
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 p. H • 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 • Response increases the original stimulus to restore homeostasis • Rarely used • Only normal when there is a definite end point • Childbirth • Blood clotting
POSITIVE FEEDBACK - CHILDBIRTH
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