nervous and synaptic transmission

• Neurons are cells that are specialised to carry neural info throughout the body
• Types of neurons

  • Sensory neuron
  • Relay neuron
  • Motor neuron
• Typical structure of a neuron

  • Dendrites
  • Cell body
  • Axon
• Dendrites

  Receive signals from other neurons or sensory receptors

  connected to cell body
• Cell body

  The control center of the neuron
• Axon

  Carries impulse in the form of an action potential
• Myelin sheath

  An insulating layer around the axon which allows impulses to travel more rapidly
• Sensory neuron

  Carries impulses from sensory receptors to CNS, converting sensory info to neural impulses
• Sensory neuron structure

  • Long dendrites
  • Short axon
  • cell body in middle
• Relay neuron

  Connects sensory and motor neurons and allows them to communicate with each other, found in CNS
• Relay neuron structure

  • Short dendrites
  • Short axon
  • No myelin sheath
  • (cell body in dendrites)
• Motor neuron


  Carries nerve impulses to muscles triggering muscle contraction
• Motor neuron structure

  • Short dendrites
  • Long axon
  • cell body on end by dendrites
• Neurotransmitter release

  1. Action potential reaches axon terminal

  2. Synaptic vesicles migrate to pre-synaptic membrane

  3. Vesicles fuse with membrane

  4. Release of neurotransmitters

  5. Neurotransmitters diffuse across synapse

  6. Bind to receptor sites on post-synaptic cell

  7.neurotransmitters are exitatory or inhibitary

  8.net effect excitatory means action potential is more likely to be triggered
• Neurotransmitters


  Chemical messengers that transmit signals across the synaptic gap to receptor sites on the postsynaptic cell
• Types of neurotransmitters

  • Excitatory
  • Inhibitory
• Excitatory neurotransmitter binding to postsynaptic neuron


  Causes an electrical change in the membrane of that cell resulting in EPSP
• If net EPSP is greater than IPSP

  Postsynaptic neuron is more likely to trigger an action potential
• Likelihood of cell firing is determined by the summation of EPSPs and IPSPs
• Dendrities receive signals from other neurons or sensory receptors and are connected to cell body which is the control centre of the neuron - from the cell body impulse is carried along the axon in the form of an action potential (electrical signal) where it terminates at the axon terminal connects the neuron to other neurons (or directly to organs),

  Mylein sheath is an insulating layer around the axon which allows impulses ot travel more rapidly