Cholinergic synapses

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Cholinergic synapses

Causes

  • An action potential arrives at the presynaptic knob of the presynaptic neuron.
  • The influx of calcium ions in the cell causes the synaptic vesicles to move towards the presynaptic membrane.
  • ACh diffuses across the synaptic cleft and binds with specific cholinergic receptors on the postsynaptic membrane.
  • An action potential is generated in the postsynaptic knob, if the threshold is reached. ACh is removed from the synaptic cleft.

Effects

  • The action potential stimulates voltage-gated calcium ion channels to open, causing Ca+ ions to diffuse into the neurone.
  • The synaptic vesicles fuse with the presynaptic membrane, and release acetylcholine into the synaptic cleft by exocystosis.
  • Na+ ion channels open in the postsynaptic membrane, triggering depolarisation in the postsynaptic neurone.
  • Acetylcholinerase breaks down acetylcholine, and the products are reabsorbed by the presynaptic neurone and used to make ACh.

Overall summary

Synaptic transmission can be disrupted by agonists ( chemicals which are the same shape as neurotransmitters)They can...- activate too many receptors,- block receptors,- inhibit enzyme activity,- inhibit the release of neurotransmitters from the presynaptic neurone, so too few receptors are activated.

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