BRAIN IMPULSE I NERVE IMPULSE I NEURON I ACTION POTENTIAL I NERVE CELL I CHEMICAL SYNAPSE
Channel: Brain Impulse
Date: 2023-02-11

A nerve cell communicates with other cells through electrical impulses when the nerve cell is stimulated. Within a neuron, the impulse moves to the tip of an axon and causes the release of neurotransmitters, chemicals that act as messengers.An action potential, also called a nerve impulse, is an electrical charge that travels along the membrane of a neuron. It can be generated when a neuron’s membrane potential is changed by chemical signals from a nearby cell. In an action potential, the cell membrane potential changes quickly from negative to positive as sodium ions flow into the cell through ion channels, while potassium ions flow out of the cell.At a chemical synapse, both the presynaptic and postsynaptic areas of the cells are full of the molecular machinery that is involved in the transmission of nerve impulses. As shown in Figure  11.4.5
 , the presynaptic area contains many tiny spherical vessels called synaptic vesicles that are packed with chemicals called neurotransmitters. When an action potential reaches the axon terminal of the presynaptic cell, it opens channels that allow calcium to enter the terminal. Calcium causes synaptic vesicles to fuse with the membrane, releasing their contents into the narrow space between the presynaptic and postsynaptic membranes. This area is called the synaptic cleft. The neurotransmitter molecules travel across the synaptic cleft and bind to receptors, which are proteins that are embedded in the membrane of the postsynaptic cell.

The effect of a neurotransmitter on a postsynaptic cell depends mainly on the type of receptors that it activates, making it possible for a particular neurotransmitter to have different effects on various target cells. A neurotransmitter might excite one set of target cells, inhibit others, and have complex modulatory effects on still others, depending on the type of receptors. However, some neurotransmitters have relatively consistent effects on other cells.