synaptic transmission

• Synapse


  The gap between two neurons
• Transmission of impulse across a synapse

  1. Action potential arrives at synaptic knob

  2. Calcium ion channels open

  3. Calcium ions diffuse into synaptic knob

  4. Vesicles fuse with pre-synaptic membrane

  5. Neurotransmitter released into synaptic cleft

  6. Neurotransmitter diffuses across synaptic cleft

  7. Neurotransmitter binds to receptors on post-synaptic membrane

  8. Sodium ion channels open

  9. Sodium ions flow into post-synaptic neuron

  10. Action potential triggered in post-synaptic neuron

  11. Neurotransmitter broken down and recycled
• Cholinergic synapse


  • Neurotransmitter is acetylcholine
  • Enzyme that breaks down acetylcholine is acetylcholine esterase
• Spatial summation


  Multiple pre-synaptic neurons attached to one post-synaptic neuron, releasing multiple neurotransmitters to trigger action potential
• Temporal summation


  One pre-synaptic neuron releasing neurotransmitter repeatedly over time to trigger action potential in post-synaptic neuron
• One action potential at pre-synaptic neuron


  Not enough neurotransmitter released to trigger action potential in post-synaptic neuron
• Multiple action potentials at pre-synaptic neuron


  Enough neurotransmitter released over time to trigger action potential in post-synaptic neuron
• Inhibitory synapse


  Neurotransmitter binds to chloride ion channels, causing hyperpolarization and making it less likely for action potential to be triggered in post-synaptic neuron
• Neuromuscular junction


  Synapse between motor neuron and muscle fiber