Apedia

Synaptic Postsynaptic Ap Presynaptic Neurone Ion Channels Open

An action potential in the postsynaptic neuron is generated when a nerve impulse reaches the presynaptic knob, causing calcium channels to open. This leads to synaptic vesicles fusing with the presynaptic membrane, releasing neurotransmitters into the synaptic cleft. The neurotransmitters bind to receptors on the postsynaptic membrane, opening sodium channels, causing sodium influx and depolarization, which triggers an action potential.

An action potential in the postsynaptic neuron is generated when a nerve impulse reaches the presynaptic knob, causing calcium channels to open. This leads to synaptic vesicles fusing with the presynaptic membrane, releasing neurotransmitters into the synaptic cleft. The neurotransmitters bind to receptors on the postsynaptic membrane, opening sodium channels, causing sodium influx and depolarization, which triggers an action potential.

Front Describe the sequence of events that occurs at a synapse that can result in an action potential being generated in post-synaptic neurone.
Back Transmission across synapse:
  • AP reaching end of presynaptic neurone causes calcium ion channels to open & calcoium ions diffuse into synaptic knob through facilitated diffusion
  • This causes synaptic vesicles to fuse with presynaptic membrane, releasing neurotransmitter into synaptic cleft - exocytosis
  • Neurotransmitter diffuses across synaptic cleft & binds to its specific receptor molecule on postsynaptic membrane
  • This causes sodium ion channels on postsynaptic membrane to open
  • Sodium ions diffuse into postsynaptic neurone, depolarising it 
  • This triggers AP and impulse is propagated along postsynaptic neurone

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