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Q3.    Explain the following processes:

         (d) Transmission of a nerve impulse across a chemical synapse

 

Answers (1)

  • synapse is formed by the membranes of the pre-synaptic neuron and the post-synaptic neuron.
  • A synapse may or may not be separated by a gap which is called the synaptic cleft.
  • At a chemical synapse, the pre-synaptic and post-synaptic neurons are separated by the synaptic cleft.
  • When an impulse arrives at the axon terminal, the calcium ions present in the synaptic cleft enter the synaptic knobs present at the axon terminals of the pre-synaptic neuron.
  • The synaptic vesicles in the synaptic knobs of the pre-synaptic neuron move towards the plasma membrane and fuse with it.
  • The vesicles release the neurotransmitter acetylcholine in the synaptic cleft. (Empty synaptic vesicles return to the cytoplasm of the pre-synaptic neuron where they are refilled.)
  • The molecules of the acetylcholine bind to the protein receptors present on the plasma membrane of the post-synaptic neurons.
  • This binding opens the channels and sodium ions enter the post-synaptic neuron, while potassium ions leave the post-synaptic membrane.
  • This generates an action potential in the membrane of the post-synaptic neuron, and hence, the impulse is transmitted to the post-synaptic neuron.
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Priyanka Kumari

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