Answer:
The correct sequence will be:
1. Action potential arrives at axon terminal.
2. Voltage-gated calcium channels open.
3. Neurotransmitter released into synaptic cleft.
4. Neurotransmitter binds to receptors.
5. Graded potential generated in postsynaptic cell.
6. Neurotransmitter is removed from the synaptic cleft.
Explanation:
The nerve impulses transmission takes place at the junction known as a synapse. At the synapse, the impulse in the form of action potential reaches at the end of the axon terminal also known as the synaptic knob of the presynaptic neuron.
This action potential results in the opening of the voltage-gated calcium channels in the membrane which leads to the influx or inside movement of the calcium ions.
These calcium ions bind to the neurotransmitters which help in the release of the neurotransmitters in the synaptic cleft. The released neurotransmitter binds to the ligand-gated receptors in the membrane of the postsynaptic membrane which leads to the opening of sodium channels.
Due to the influx of sodium ions in the post-synaptic neuron causes depolarization of the neuron and the potential is generated in the neuron.
Thus, the marked sequence is correct.
