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A neuron is a particular kind of cell that is specialized for the storage and transmission of information. Neurons are found in the brain as well as in the brainstem and spinal cord; they are also the nerve cells which transmit information to muscles and which register sensory information (e.g. touch stimuli).

Neurons release chemicals called neurotransmitters into a small gap called the synapse. Other neighboring neurons receive these chemicals and their activity may be altered. Neurons vary widely in size, shape and in the neurotransmitters they release. Most neurons have three recognizable components: a cell body, an axon an

Most neurons have three recognizable components: a cell body, an axon and dendrites. The cell body contains the machinery needed to convert nutrients to energy and keep the cell alive. The dendrites are input areas that contain receptors; each receptor is specialized to respond to a particular kind of neurotransmitter. If enough receptors are activated, the neuron may become active itself. In this case, an electrical charge is generated and passes down the axon, the output process of the neuron. The axon can vary from a few millimeters to several inches in length, and can branch widely. When the electrical charge reaches the tip of the axon, neurotransmitters are released. These neurotransmitters may in turn activate receptors on the dendrites of neighboring neurons, passing the message along.

There are between 10 billion and 100 billion neurons in the brain; each neuron may contact about 1000 others. The basic mechanism of learning is believed to be the alteration in connections or connection strengths between neurons (see also long-term potentiation).