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specialized cell in animals that, as a unit of the nervous systemnervous system,
network of specialized tissue that controls actions and reactions of the body and its adjustment to the environment. Virtually all members of the animal kingdom have at least a rudimentary nervous system.
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, carries information by receiving and transmitting electrical impulses.



(or nerve cell), the basic structural and functional unit of the nervous system.

A neuron receives signals that enter from receptors and other neurons and processes and transmits the signals in the form of nerve impulses to the effector nerve endings, which control the activities of the corresponding organs of response (muscles, gland cells, or other neurons). Neurons differentiate from neuroblasts, which arise in the neurula stage of embryonic development.

In the process of differentiation a neuron develops specialized structures to ensure the performance of the various neuronal functions. Branched outgrowths, or dendrites, are specialized to receive information; these structures have a receptive membrane and are sensitive to specific physiological stimuli. The excitatory and inhibitory processes that are localized in the receptive membrane accumulate and act on the stimulus region, the most excitable area of the surface membrane of the neuron; this serves as the origin for the spreading bioelectric potentials. The longest outgrowth, the axon (or axis cylinder), is covered by an electrically excitable conducting membrane that serves to transmit the potentials. Having reached the terminal sections of the axon, the nerve impulse excites the secretory membrane; as a result of this, a physiologically active substance, either a mediator substance (chemical transmitter) or a neurohormone, is secreted from the nerve endings.

In addition to structures associated with the performance of specific functions, a neuron has a nucleus (as do all living cells) that, together with the perinuclear cytoplasm, forms the cell body, or perikaryon. It is here that synthesis of macromolecules takes place. Some of these are transported along the axoplasm (the cytoplasm in the axon) to the nerve endings.

The structure, dimensions, and shape of neurons vary widely. Neurons of the cerebral cortex, cerebellum, and some other areas of the central nervous system have complex structures. Multipolar neurons are characteristic of the brain of vertebrates. In such neurons, several dendrites and one axon emerge from the cell-body; the initial section of the axon serves as the excitatory region. Numerous nerve endings from the outgrowths of other neurons converge on the cell body and dendrites of a multipolar neuron. The ganglia of invertebrates usually consist of unipolar neurons; the cell body only fulfills a trophic function and is connected with the axon at the axon hillock. It would appear that such a neuron does not necessarily have true dendrites, and reception of synaptic signals is effected by specialized areas on the surface of the axon. Neurons with two outgrowths are called bipolar; they occur most often as peripheral sensory neurons having one axon and one dendrite, which impinges on the cell surface.

Neurons are classified according to their position in a reflex arc: afferent, or sensory, neurons receive information from the external environment or from receptor cells; interneurons, or internuncial neurons, connect one neuron with another; efferent neurons transmit impulses to the organs of response (for example, motoneurons innervate muscles).

Neurons are also classified according to their chemical specificity, that is, according to the nature of the physiologically active substance that is secreted by the nerve endings of a given neuron. For example, a cholinergic neuron secretes acetylcholine and an adrenergic neuron secretes adrenaline. The number of neurons present in a nervous system determines the variety and complexity of functions that an organism can perform; for example, there are 102 neurons in the Rotatoria and more than 1010 in man.


Eccles, G. Fiziologiia nervnykh kletok. Moscow, 1959. (Translated from English.)
Hyden, H. “Neiron.” (Translated from English.) In the collection Funktsional’naia morfologiia kletki. Moscow, 1963.
Mekhanizmy deiatel’nosti tsentral’nogo neirona. Moscow-Leningrad, 1966.
Nervnaia kletka: sb. st. Edited by N. V. Golikov. Leningrad, 1966.



A nerve cell, including the cell body, axon, and dendrites.


References in periodicals archive ?
Hematoxylin-eosin sections revealed neuronal loss and gliosis that was greatest in language regions, and numerous ballooned neurons in cortical and subcortical regions and brainstem nuclei (Figure 11, B) that were labeled with antibodies to phosphorylated tau (Figure 11, C).
12,25,26) Progressive declines in NAA and tNAA, consistent with neuronal loss, have been observed in Sandhoff patients.
The finding also demonstrated that anti-inflammatory cytokines could contribute to neuronal loss.
Indeed, postmortem studies support this finding, showing neuronal loss (Baker et al.
David Poulsen and his colleagues at the University of Montana applied the stimulant to rat-brain sections they subsequently deprived of oxygen and found that those given meth had less neuronal loss.
Focal cortical atrophy marked by neuronal loss, gliosis, and spongiform degeneration was present (Figure 4).
39,40] This is probably the result of a combination of age-related changes in the hair cells at the center of the cristae, [34] a relatively selective loss of large-diameter primary vestibular afferents, and neuronal loss in the superior vestibular nuclei.
Since neuronal loss is a characteristic neuropathologic feature of AIDS dementia complex, our data on AIDS-demented patients suggest that increased CSF protein [tau] concentrations might not depend on neuronal death alone.
We're still left with the problem of selective neuronal loss," says Michael Hayden of the University of British Columbia in Vancouver.
Unfortunately, patients often incur up to 50% neuronal loss and a delay of up to two years before demonstrating severe enough symptoms to achieve diagnosis by the current gold standard: a 'process of elimination' of other possible diagnoses such as stroke, trauma, Parkinson's disease, dementia, etc.
DP-b99 was neuroprotective against kainate induced neuronal loss and prevented MMP-9-mediated dendritic spine transformation.

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