Explain the following processes :
Transmission of a nerve impulse across a chemical synapse.

Explanation

Transmission of a nerve impulse across a chemical synapse : A nerve impulse is transmitted from one neuron to another through junctions called synapses. At a chemical synapse, the membranes of the pre- and post-synaptic neurons are separated by a fluid-filled space called synaptic cleft. Chemicals called neurotransmitters are involved in the transmission of impulses at these synapses. The axon terminals contain vesicles filled with these neurotransmitters. When an impulse arrives at the axon terminal, it stimulates the movement of the synaptic vesicles towards the membrane where they fuse with the plasma membrane and release their neurotransmitters in the synaptsic cleft. The released neurotransmitters bind to their specific receptors, present on the post-synaptic membrane. The binding opens ion channels allowing the entry of ions which can generate a new potential in the post-synaptic neuron.