neurons

• Types of neurons


  • Sensory
  • Relay
  • Motor

  
• Sensory neurons


  • Found in receptor cells (e.g. eyes and skin)
  • Carry nerve impulses to the spinal cord and brain
  • Translate nerve impulses into 'sensations' (e.g. vision and touch)
  • Some do not reach the brain, allowing for quick reflex actions

  
• Relay neurons


  • Found in between sensory input and motor output/response
  • Found in the brain and spinal cord
  • Allow sensory and motor neurons to communicate

  
• Motor neurons


  • Found in the central nervous system (CNS)
  • Control muscle movements
  • Release neurotransmitters that bind to receptors on muscles to trigger a response

  
• Dendrites


  Receive signals from other neurons or from sensory receptor cells
• Axon


  A long slender fibre that carries nerve impulses, in the form of an electrical signal known as action potential
• Myelin sheath


  Insulates the axon so that the electrical impulses travel faster along the axon
• Axon terminal


  Connects the neuron to other neurons (or directly to organs), using a process called synaptic transmission

  
• Synaptic transmission


  1. Information is passed down the axon of the neuron as an electrical impulse (action potential)

  2. Action potential reaches the end of the axon and needs to be transferred to another neuron or tissue, by crossing the synaptic gap

  3. Synaptic vesicles in the axon terminal contain neurotransmitters

  4. Electrical (nerve) impulse (action potential) stimulates the release of the neurotransmitters from the synaptic vesicles

  5. Neurotransmitters carry the signal across the synaptic gap and bind to receptor sites on the postsynaptic cell which then become activated

  
• Excitatory neurotransmitters


  Make the post synaptic cell more likely to fire (e.g. noradrenaline)
• Inhibitory neurotransmitters


  Make the post synaptic cell less likely to fire (e.g. GABA)
• Summation


  The net effect of the EPSPs and IPSPs (adding up the positive and negative charges)
• Briefly outline how excitation and inhibition are involved in synaptic transmission.