Question

Describe the structures involved in a typical chemical synapse (e.g., axon terminal [synaptic knob], voltage-gated calcium channels, synaptic vesicles of presynaptic cell, synaptic cleft, neurotransmitter receptors of the postsynaptic cell).

Answer 1

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• Synapse is the connection or junction between the two neurons.
• Synapse is formed by the axon of the one neuron and dendrite or axon of the next neuron.
• Terminal knobs or terminal axon - The terminal portion of the axon where synapse occurs is enlarged and known as terminal knob.
• The presynaptic membrane contains calcium channel.
• The postsynaptic membrane contains receptors for the neurotransmitter.
• Synaptic vesicles contains neurotransmitter.
• The space between the presynaptic neuron and postsynaptic neuron is called as synaptic cleft.
• As the action potential arrives in the axon terminal, calcium channels open in the presynaptic membrane and causes entry of calcium ions from the extracellular fluid into the axon terminal.
• Opening of the synaptic vesicles releases the neurotransmitter.
• The neurotransmitter passes through synaptic cleft and the receptors present on the postsynaptic membrane forms complex with it.
• Then, sodium channels open into the postsynaptic membrane and there is influx of sodium ion occurs from the extracellular fluid.
• Due to the influx of the sodium ion action potential occurs in the neuron.