MEDICAL PHYSIOLOGY

Detailed explanation-1: -Neurotransmitter is stored inside small sacs called synaptic vesicles, and is released into the synaptic cleft of the synapse when a vesicle fuses with the cell membrane. This process, which is known as exocytosis, can release neurotransmitter in less than a millisecond.

Detailed explanation-2: -Depolarization of the membrane causes voltage-gated Ca2+ channels to open and Ca2+ to enter the cell. The intracellular calcium influx causes synaptic vesicles containing neurotransmitter to fuse with the presynaptic membrane.

Detailed explanation-3: -During the depolarization phase, the gated sodium ion channels on the neuron’s membrane suddenly open and allow sodium ions (Na+) present outside the membrane to rush into the cell. As the sodium ions quickly enter the cell, the internal charge of the nerve changes from-70 mV to-55 mV.

Detailed explanation-4: -In neurons, the rapid rise in potential, depolarization, is an all-or-nothing event that is initiated by the opening of sodium ion channels within the plasma membrane.