nerve tissue + impulses

• what happens when the stimulus is activated by the nerve impulse?

  Response: Action potential
• what is action potential?

  Electrical signal in neurons that allows for communication between cells. (stimulus)
• what happens once a stimulus occur?

  some Na+ channels open up ( resting potential-70 )
• what is depolarisation?

  once the stimulus reaches -55 , voltage-gated Na+ channels open sending them into the axon
• what is repolarisation

  after depolarisation Na+ channels close and voltage-gates K+ channels open (-90)
• what is hyper-polarisation

  some K+ channels stay open and the nerve goes back to resting (-70)
• order of nerve impulses

  stimulus occurs

  depolarisation

  re-polarisation

  hyper-polarisation
• Dendrite

  Receives signals from axon terminals
• Cell body

  Contains the nucleus of the neuron
• Axon

  Transmits signals away from the cell body
• Axon terminal

  Where the axon connects to other neurons
• Schwann cell


  Produces the myelin sheath around the axon
• Nerve tissue

  Transmits signals
• Signals travel along the axon
• non-myelinated nerve cell

  • small diameter
  • no melin sheath
  • grey
  • slow impulse
  • no nodes of ranvier
  • transmits aches and temp changes
• myelinated ( most nerve cells are )

  • large diameter
  • have myelin sheath
  • white
  • fast impulses ( action potential)
  • nodes of ranvier
  • transmits sharp pains
• Motor neurone


  From CNS to effectors
• relay neurone 


  found in the CNS
• sensory neurone


  from sensory receptors to the CNS
• what do Na and K ions rely on to move in and out of the axon?

  diffusion ( movement from high concentration to low concentration)
• myelin sheath is an insulating layer around the axon made up of fatty molecules called lipids.

  
• the axon is the long, thin part that carries electrical signals away from the cell body.