Neurons and Synaptic Transmission

• What are the three types of Neurons

  Sensory Neuron(senses), Relay/Interconnecting Neuron (relay race) & the Motor Neuron (movement)
• Characteristics of the neurons

  • Sensory Neuron: [Function] - carries messages from the PNS to the brain and the spinal cord, [Length of Fibres] - long dendrites and short axons
  • Relay Neuron: [Function] - Transfers messages from sensory neurons to other interconnecting neurons or motor neurons, [Length of Fibres] - short dendrites and short or long axons
  • Motor Neuron: [Function] - Carries messages from the CNS to effectors like muscles and glands, [Length of Fibres] - short dendrites and long axons
• Structure of Neurons


  • Nucleus - contains all the genetic information of the cell
  • Cell body/Soma - contains the nucleus
  • Dendrites - carry nerve impulses from neighbouring neurons towards the cell body
  • Axon - take nerve impulses away from the cell body down the neuron
  • Myelin sheath - a fatty layer that protects the axon and speeds up transmission of the nerve impulse (gaps between the myelin sheath prevent nerve impulses from slowing down)
  • Nodes of Ranvier (in the myelin sheath gaps) - maintain the speed of the nerve impulse by forcing impulses to 'jump' across the gaps
  • Terminal buttons (at the end of the axon) - they communicate with the next neuron in the chain across the synapse
  • Synapse - The gap between two neurons
• What are the types of neurotransmitters

  • Excitatory - they increase the positive charge and the likelihood of an action potential firing in the next neuron i.e. adrenaline
  • Inhibitory - increases the negative charge and decreases the likelihood of an action potential firing in the next neuron i.e. serotonin
• synaptic uptake


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