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Neuron: Structure and Function
Nerve cells or neurons are especially adapted to receive and transmit signals. They play equally important role in the transmission of information. Figure 3.1 illustrates the basic structure of a neuron
All neurons share three fundamental components- soma, dentrites and axon. Structurally soma or the cell body contains nucleus and other structures present in other cells of our body. Most of the cytoplasm of the neuron is contained in the soma. Dentrites come out from the soma and carry message into the neurons. Dendrites have small bumps known as dendritic spines which can receive signals from other neurons. Axon is the extension carrying signals from cell body to the terminal buttons at the end of the neurons. These terminal buttons contain neurotransmitters which plays important role in conduction at synapse. Synapse is the junction where one neuron ends and the other begins. Any two neurons are not directly connected to each other; rather they are separated by about  of a micron. These gaps are called synaptic cleft. The part of axon nearest to the soma is called axon hillock. Thereafter, it branches into telodendria and finally translates to end feet or terminal buttons. Few neurons have a fatty insulation through out the axon called myelin sheath. This insulation is segmented at 1-2 mm interval such that it looks like disjointedly arranged divisions. These spaces are called nodes of Ranvier (Fig. 3.2). The rate of conduction of impulses in myelinated neurons is higher than the unmyelinated ones.
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