transmission across a cholinergic synapse

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  • Transmission across a cholinergic synapse
    • The neurotransmitter which occurs in the synapse is called acetylcholine.
      • It controls the central nervous system and at neurotransmitters in vertebrates.
    • Transmission across a cholinergic synapse occurs as follows
      • 1. The arrival of an action potential at the presynaptic membrane causes the calcium ion gates to open and calcium ions enter the presynaptic neurone.
      • 2. The influx of calcium ions in the presynaptic membrane causes synaptic vesicles to fuse with the presynaptic membrane, releasing the aceytlcholine into the synaptic cleft.
      • 3. Acetylcholine molecules fuse with receptor sites on the sodium ion channels on the post synaptic membrane, causing the sodium ion channels, allowing sodium ions to diffuse in rapidly along their concentration gradient.
      • 4. The influx of sodium ions generates a new action potential in the post synaptic neurone.
      • 5. Acetylcholinesterase hydrolyses acetylcholine into choline and ethanoic acid which diffuses back across the synaptic cleft into the pre synaptic cleft for recycling.
      • 6. In addition to recycling the choline and ethonic acid, the breakdown of acetylcholine also prevents it from continuously generating an action potential in the post synaptic neuron.
      • 7. ATP released by the mitochondria is used to recombine choline and ethonic acid into acetylcholine. This is stored in the synaptic vesicles for future use. Sodium ion channels close in the absence of acetylcholine in the receptor site
    • Effects of drugs on synpases
      • They stimulate the nervous system by creating more action potentials in the post synaptic neurones.
        • By mimicking the neurotransmitter
        • Stimulating the release of neurotransmitters
        • Inhibiting the enzyme which breaks down the neurotransmitter
      • They inhibit the nervous system by creating fewer action potentials in the postsynaptic neurones
        • Inhibiting the production of the neurotransmitter
        • Blocking the receptors on the post synpatic neurone.
      • The overall effect of the drug depends on the type of neurotransmitter its disrupting,


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