Homeostasis Overview

Homeostasis Overview

1. Negative feedback

   • Inhibits stimulus
     • Return to ideal
       • SET POINT
     • Maintenance of equilibrium
   • Change in variable
     • Detected by receptor
       • Processed in integration centre
         • Effector response
           • Return to....
           • Usually activated by autonomic nervous system
         • Normally in medulla
       • Transmitted by sensory neurones
   • EXAMPLES
     • High blood pressure
       • Reduced cardiac output
       • Vasodilation
     • Hyperglycaemia
       • Release of insulin

2. Positive feedback

   • Enhance stimulus
     • Divergence from equilibrium
   • EXAMPLES
     • Blood clotting
       • Platelets at clot release chemical to attract more platelets
         • Clot formed
     • Childbirth
       • Oxytocin released, stimulates contractions
         • Contractions stimulate release of more oxytocin
           • Continues until birth

3. Keeping vital parameters within narrow limits

   • Core body temperature
   • Heart rate
   • Blood pressure
   • Blood glucose
   • Osmolarity of plasma
   • Urine concentration

4. Rapid and efficient communication around body

   • Nervous system
     • Autonomic
     • Electrical communication
   • Endocrine system
     • Hormones
     • Chemical communication