Neuron Structure

<h1>Text Preview</h1> <p>Neurons are generally composed of three parts. The cell body contains the nucleus and organelles. Dendrites and axons branch off from the cell body. Dendrites conduct neuronal messages toward the cell body. Axons conduct neuronal messages away from the cell body. </p> <p>The proteins embedded in the plasma membrane play a crucial role in maintaining the strength of the message along the length of the neuron. Almost all axons and dendrites are surrounded by accessory cells. These cells create a protective sheath that also affects the speed of neuronal signaling. This sheath is made of myelin, the protein and lipids left after the cells that surround the axon eventually lose their cytoplasm during the development of the nervous system. Myelin can be destroyed by processes encountered in hereditary disorders, such as leukodystrophy, and in acquired diseases, such as multiple sclerosis. </p> <p>The plasma membrane of a neuron contains many proteins that determine neuron function. These proteins include receptors, ion pumps, and ion channels. Special ion channels, found only in cells like neurons, play an important role in propagating the action potential. Ion channels are found all along the axons of non-myelinated neurons and at the gaps in the myelin of myelinated axons.</p> <p>Signals within a neuron are transmitted via action potentials down its axon. Incoming signals are received by the dendrites and the cell body. The signals may make the interior of the cell membrane more negative or more positive relative to the outside. These signals are added up and it is the sum of these that determines whether an action potential will be sent by the target cell. Axons terminate at the synapse, the space between two neurons where communication takes place.</p> <p>The axon shown here is enlarged and filled with vesicles containing neurotransmitters. Neurotransmitters are the chemical signals of the nervous system. When released by an axon, they diffuse across the synapse where they encounter receptors specific to that neurotransmitter.</p> <p>Now that we’re familiar with the anatomy of a neuron, let’s see how neurons transmit their messages.</p> <p id="TextCopyright">Copyright 2006 The Regents of the University of California and Monterey Institute for Technology and Education</p>