reflex arc

• sensory neurone


  found in receptors such as eyes, ears, skin and carry nerve impulses to the spinal cord and brain. When these impulse reach the brain they are converted into 'sensations' such as visions, hearing and touch.

  not all sensory neurones reach the brain, some stop at spinal cord for quick reflex actions
• relay neurone


  found between sensory and motor response

  found in the brain and spinal cord and allow sensory and motor neurones to communicate
• motor neurones 


  found in the central nervous system and control muscle movements

  when motor neurone are stimulated they release neurotransmitters that bind to trigger a response which lead to movement
• structure of sensory, motor and relay neurones 


  :

  
• parts of a neurone


  dendrites: receive signals from other neurones, typically connected to cell body

  cell body: control centre, contains nucleus

  axon: long fibre that carries nerve impulses, as action potentials away from cell body towards axon terminals where neurone ends

  myelin sheath: insulates axon and speeds up electrical impulses

  axon terminal: connects neurone to other neurones through synaptic transmission
• reflex arc

  • information detected by sensory neurones. Then taken from PNS to CNS
  • information delivered to relay neurone across synapse between sensor neurone and relay neurone dendrite. Play neurone passes messages across CNS
  • the motor neurone receives the message from the relay neurone and transmits this to an effector - could be to move muscle or release hormone
  • process involving sensory + motor neurone is faster as myelin sheaths speed transmission via saltatory conduction
• structure of neurones 


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