Neurons and How They Work

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Look this amazing video about neurons, who are specialized to carry "messages" through an electrochemical process.

The main portion of the cell is called the soma or cell body. It contains the nucleus, which in turn contains the genetic material in the form of chromosomes.
One extension is different from all the others, and is called the axon.

The purpose of the axon is to transmit an electro-chemical signal to other neurons, sometimes over a considerable distance. Longer axons are usually covered with a myelin sheath, a series of fatty cells which have wrapped around an axon many times. These make the axon look like a necklace of sausage-shaped beads. They serve a similar function as the insulation around electrical wire.

Neurons have a large number of extensions called dendrites. They often look likes branches or spikes extending out from the cell body. It is primarily the surfaces of the dendrites that receive chemical messages from other neurons.
At the very end of the axon is the axon ending, which goes by a variety of names such as the bouton, the synaptic knob, the axon foot, and so on.

It is there that the electro-chemical signal that has travelled the length of the axon is converted into a chemical message that travels to the next neuron.
Between the axon ending and the dendrite of the next neuron is a very tiny gap called the synapse (or synaptic gap, or synaptic cleft), which we will discuss in a little bit. For every neuron, there are between 1000 and 10,000 synapses.

The synapse

When the action potential reaches the axon ending, it causes tiny bubbles of chemicals called vesicles to release their contents into the synaptic gap. These chemicals are called neurotransmitters. These sail across the gap to the next neuron, where they find special places on the cell membrane of the next neuron called receptor sites.

video: Synaptic vesicles fuse with the presynaptic membrane, freeing neurotransmitter molecules into the synaptic space

3D animation of a neuron and an action potential. Ion channels in the soma open and allow an increase in the intracellular voltage. Once the voltage reaches a threshold, an action potential is generated, which travels the length of the axon and passes into the terminals. The voltage in the terminals stimulate the release of neurotransmitters which cross the synapse, opening ion channels in dendrites of the post-synaptic neuron and increasing the voltage of the second neuron.

video: Neurons and How They Work