neuronal communication

• what is a reflex action 


  a fast automatic unconscious response to protect you form harm
• reflex arc 


  the arrangement of the neurones involved in a reflex action
• reflex actions

  A) spinal nerve (mixed sensory and motor neurones)

  B) Dorsal Root Ganglion

  C) cell bodies os sensory neurones

  D) grey matter (neurone cell bodies)

  E) spinal canal (contains cerebrospinal fluid)

  F) spinal cord

  G) ventral root (motor neurones)

  H) white matter (neurone axons)

  
• nerve impulse

  the passage of an action potential along a neurone.
• The nature of the nerve impulse was discovered by Hodgkin and Huxley in the 1930's as a result of their work on the giant axons (1mm in diameter) from a squid.
• • Action potentials do not change in size as they travel

  • However long an axon, the action potential will continue to be +40mV along its length.

  • The intensity of the stimulus has absolutely no effect on the size of the action potential

  • The speed at which the action potentials travel does not vary according to the size of the stimulus

  • In any one axon, transmission is always the same

  • A strong stimulus will generate more action potentials whilst a weak stimulus will not generate so many action potentials