Question

Do you know how the presynaptic neuron transmits an impulse (action potential) across the synaptic cleft to the postsynaptic neuron?

Answer 1

Neurotransmitters are molecules that neurons use in the phase of synaptic transmission (neurotransmission) to interact with each other and to their target tissues. Their function is to convey signals to target sites from nerve cells.

Complete answer:
In the synaptic cleft, neurotransmitters are synthesized and are liberated from the nerve endings. The human nervous system has much more than 40 neurotransmitters, including acetylcholine, dopamine, gamma-aminobutyric acid (GABA), serotonin and histamine are amongst the most significant. Innumerable vesicles that contain neurotransmitters are stored within the terminal button of the presynaptic nerve fibre. Whenever an action potential depolarizes the presynaptic membrane, calcium voltage-gated channels extend. This results in an influx of calcium ions into the terminal press, that alters the state of many membrane proteins in the presynaptic membrane, resulting in exocytosis of terminal neurotransmitters. These neurotransmitters go and bind to the receptors of the postsynaptic neuron generating an action potential. Neurotransmitters on the postsynaptic membrane bind to the voltage-gated ion channels causing the depolarization of the membrane. Different stages of the action potential can be observed in the neuron, which includes; depolarization, repolarization, hyperpolarization and back to the normal state, i.e. depolarization again. The signal in a nerve cell is mainly conducted by the axon.

Note: Neurotransmitter high-affinity processing is mediated by transporter proteins and it is the most common mechanism for neurotransmitter signalling cessation. Some of the disorders connected with neurotransmitters are Alzheimer’s, depression, Parkinson’s, epilepsy, etc.