Question

Describe neuronal synapses, including the pre-synapse (morphology, ion channels, receptors), the synaptic cleft (neurotransmitters, glial cell involvement), and post-synapse (morphology, ion channels, receptors)

Answer 1

SYNAPSES

                   A nerve impulse is transmitted from one neuron to another through junctions called synapses.A synapse is formed by the membrane of a pre-synaptic neuron and a post-synaptic neuron which may or may not be seperated by a gap called synaptic cleft.

                  Pre-synaptic membrane is the area of a neuron where a impulse reaches at last (axon terminal) and tries to pass on to next neuron.It is the area where neurotransmitters are being synthesised and then stored in vesicles.Exocytosis is the process occuring for the transfer of impulse with the help of neurotransmitter.When a action potential reaches pre-synaptic terminal,its depolarisation causes opening of voltage gated calcium ions channels and they enter.Calcium ions then causes the vesicles to fuse with pre-synaptic membrane.Then the neurotransmitter is released into synaptic cleft via exocytosis.

                 Synaptic ceft is an area between two axons where neurotransmitters are being released.They are mostly seen in the chemical synapses rather than electrical synapses.The vesicles release neurotransmitter and then the remaining vesicles are being taken into glial cell for the preperation for new neurotransmitter containing vesicles or by enzymatic degradation.

                Post-synaptic membrane is the area where released neurotransmitters are being taken to induce the continuos stimulus for the specific purpose.The neurotransmitter binds to receptor molecules in the post-synaptic membrane via opening or closing of postsynaptic channels.Post-synaptic current causes excitatory or inhibitory post-synaptic potential that changes the excitability of the post-synaptic cell.