Feedback

• Feedback

  • Homeostasis:
  • Constant internal environment maintenance
  • Despite external
  • Physiological factors control in mammals:
  • Body temperature
  • Blood glucose
  • Salt
  • Water potential
  • Pressure
  • Tissue CO_2 concentration
  • Negative:
  • Reverse any change internal environment condition
  • Maintain optimum
  • Detect change (stimulus) -> Signal to other cells -> Response occurs to reverse
  • Positive:
  • Increases detected change
  • Normally harmful
  • Not homeostasis (destabilises)
  • Insulin Receptor: Put glucose transporter proteins in membranes; more glucose enters; membrane more permeable
• Positive Feedback Examples

  • Too low body tempe
  • Activity fall
  • Exergonic reactions (respiration) releasing thermal energy slower
  • Body keeps cooling
  • Reactions too slow to support life (hypothermia and death)
  • Frostbites effect on tissues:
  • Freeze peripheral tissues/extremities
  • Numb
  • Water in tissues + cells freezes
  • Gangrene may occur (when thawed)
  • Oxytocin (posterior pituitary gland)
  • Uterus contraction, start labour
  • Contractions stimulate oxytocin, causes more contractions
  • Milk in breast-feeding
  • More baby sucks, more oxytocin released and milk ejected
  • Beneficial