Label The Parts Of Nerve Cell
Check us out at http://www.tutorvista.com//videos Despite the specific molecular, morphological, and functional features of any particular nerve cell type, the basic structure of neurons resembles that of other cells. Thus, each nerve cell has a cell body containing a nucleus, endoplasmic reticulum, ribosomes, Golgi apparatus, mitochondria, and other organelles that are essential to the function of all cells). These features are best recognized using the high magnification and resolution afforded by the electron microscope. The distinguishing characteristic of nerve cells is their specialization for intercellular communication. This attribute is apparent in their overall morphology, in the specialization of their membranes for electrical signaling, and in the structural and functional intricacies of the synaptic contacts between them. A particularly salient morphological feature of most nerve cells is the elaborate arborization of the dendrites (also called dendritic branches or dendritic processes) that arise from the neuronal cell body. The spectrum of neuronal geometries ranges from a small minority of cells that lack dendrites altogether to neurons with dendritic arborizations that rival the complexity of a mature tree . The number of inputs that a particular neuron receives depends on the complexity of its dendritic arbor: Nerve cells that lack dendrites are innervated by just one or a few other nerve cells, whereas those with increasingly elaborate dendrites are innervated by a commensurately larger number of other neurons. The dendrites (together with the cell body) provide the major site for synaptic terminals made by the axonal endings of other nerve cells. The synaptic contact itself is a special elaboration of the secretory apparatus found in most polarized epithelial cells. Typically, the presynaptic terminal is immediately adjacent to a postsynaptic specialization of the contacted cell. For the vast majority of synapses, there is no physical continuity between these pre- and postsynaptic elements. Instead, the pre- and postsynaptic components communicate via secretion of molecules from the presynaptic terminal that bind to receptors in the postsynaptic specialization. These molecules must traverse the extracellular space between pre- and postsynaptic elements; this interruption is called the synaptic cleft. The number of synaptic inputs received by each nerve cell in the human nervous system varies from 1 to about 100,000. This range of inputs reflects a fundamental purpose of nerve cells, namely to integrate information from other neurons. The number of inputs onto any particular cell is therefore an especially important determinant of neuronal function.