positive feedback

• positive feedback does not maintain a constant internal environment so is not involved in homeostasis
• overview

  • when the original stimulus produces a response that causes factors to deviate even more from the normal range
  • enhances the effect
• dialation of cervix during labour(example)

  • the cervix stretches as baby pushes against it
  • stretch receptors are stimulated and send impulses to the brain
  • pituitary gland produces oxytocine which increases intensity of uterine contractions
  • pushes baby further down birth canal and cervix stretches further
• blood clotting(example)

  • platelets are activated
  • release chemicals which activate more platelets
  • this continues, blood clotting continues and would is quickly closed