homeostasis, the nervous system, reflexes

• homeostasis 


  maintains optimal conditions for enzyme action (as well as all cell functions) throughout the body
• examples of homeostasis 


  blood glucose concentration, body temp, water levels
• chemical responses are from the

  endocrine system
• the central nervous system 


  brain and spinal chord
• peripheral nervous system 


  nerve cells that carry information to or from cells
• two ways the conditions in the body are controlled

  chemical and nervous
• receptors


  detect stimuli
• stimuli


  changes in the environment
• coordination centre 


  what receives and processes information from receptors around the body e.g brain, spinal chord or pancreas
• effectors 


  bring about responses which restore optimum levels. effectors include muscles and glands, therefore, responses can include muscle contractions or hormone release.
• all control systems include

  receptors

  a coordination centre

  effectors ( to bring about response )
• nerve cells


  neurones
• neurones are adapted to 


  carry electrical impulses from one place to another
• a bundle of neurones

  nerve
• 3 main types of neurones

  sensor

  relay

  motor
• insulates the axon


  fatty (myelin ) sheath
• axon


  long fibre ( long so they can carry messages up and down the body )
• dendrones 


  tiny branches which branch furhter into dendrites at each end
• dendrones / dendrites receive 


  incoming impulses from other neurones
• labelled diagram

  motor nuerone

  A) nerve ending

  B) cell membrane

  C) axon

  D) nucleus

  E) dendron

  F) cytoplasm

  
• electrical impulses 


  information from receptors passing along neurones
• where electrical impulses go to

  coordinators such as the cns
• cns


  brain and spinal chord
• muscles contracting or glandds secreting hormones 


  the response of ffectors coordinated by the cns
• created by reflex actions 


  automatic and rapid response
• an automatic / rapid response means


  minimising damage to the body
• why would an automatic / rapid response be needed


  becasue of potentially harmful conditions
• reflex action does not involve

  conscious part of brain
• general sequence that reflex actions follow

  stimulus

  receptor

  sensory neurone

  relay neurone

  motor neurone

  effector

  response
• a reflex action has

  different types of neurones working together
• reflex arc

  the nerve pathway followed by a reflex action
• (simple reflex arc) receptor in skin detects 


  stimulus
• (simple reflex arc) sensory neurone sends


  electrical impulses to relay neurone
• where is relay neurone located


  spinal chord
• (simple reflex arc) motor neurone sends 


  electrical impulses to effector
• (simple reflex arc) effector produces 


  a response
• synapse 


  small gap between where two neurones meet
• reflex action is an automatic response that occurs when there is danger or threat to our body.
• The reflex arc allows us to respond quickly to stimuli without conscious thought.