Question

Describe the steps involved in neurotransmitter release from a synapse and generation of postsynaptic excitatory postsynaptic current?

Answer 1

Steps involved in neurotransmitter release from a synapse:

Neurotransmitter release from a synapse consists of a series of intricate steps:

1) depolarization of the terminal membrane,

2) activation of voltage-gated Ca²⁺ channels,

3) Ca²⁺ entry,

4) a change in the conformation of docking proteins,

5) fusion of the vesicle to the plasma membrane, with subsequent release of neurotransmitter into the synaptic cleft.

Steps involved in generation of postsynaptic excitatory postsynaptic current:

(1)Temporary depolarization of postsynaptic membrane caused by the flow of positively charged ions into the postsynaptic cell as a result of opening of ligand-sensitive channels.

(2)An excitatory postsynaptic potential (EPSP) is received when an excitatory presynaptic cell, connected to the dendrite, fires an action potential.

(3)The EPSP signal is propagated down the dendrite and is summed with other inputs at the axon hilllock.

(4)The EPSP increases the neurons membrane potential.

(5)When the membrane potential reaches threshold the cell will produce an action potential & an excitatory postsynaptic current.