- Neuron
- A nerve cell, the basic impulse-conducting unit of the nervous system. Neurons send and receive electrical signals over long distances within the body. A neuron may send electrical output signals to muscle neurons (called motor neurons or motoneurons) and to other neurons. A neuron may receive electrical input signals from sensory cells (called sensory neurons) and from other neurons. A neuron that simply signals another neuron is called an interneuron. The connections between neuron are the synapses. (So if you are not thinking clearly, blame it on poor synapses!) The word "neuron" comes straight from the Greek meaning "a sinew, tendon, thong, string, or wire." The term was introduced to designate a nerve cell by the English physiologist Sir Charles Scott Sherrington (1857-1952). Sherrington was an influential figure in the development of neurophysiology (the intersection between neurology and physiology), clinical neurology and neurosurgery ("brain surgery"). He worked at Oxford University. Aside from the "neuron," he also coined other useful terms including "synapse." Sherrington shared the Nobel Prize in Medicine or Physiology in 1932 with Lord Edgar Douglas Adrian of Cambridge University for "their discoveries regarding the functions of neurons."
* * *The morphologic and functional unit of the nervous system, consisting of the nerve cell body, the dendrites, and the axon. SYN: nerve cell, neurocyte, neurone. [G. n., a nerve]- intercalary n. SYN: internuncial n..- internuncial n. a n. interposed between and connecting two other neurons. SYN: intercalary n..- lower motor n. clinical term used to indicate the final motor neurons that innervate the skeletal muscles; distinguished from upper motor neurons of the motor cortex that contribute to the corticospinal tract. SEE ALSO: motor n..- motor n. a nerve cell in the spinal cord, rhombencephalon, or mesencephalon characterized by having an axon that leaves the central nervous system to establish a functional connection with an effector (muscle or glandular) tissue; somatic motor neurons directly synapse with striated muscle fibers by motor endplates; visceral motor neurons or autonomic motor neurons (preganglionic m. neurons), by contrast, innervate smooth muscle fibers or glands only by the intermediary of a second, peripheral, n. (postganglionic m. n.) located in an autonomic, or visceral motor, ganglion. SEE ALSO: motor endplate, autonomic division of nervous system. SYN: anterior horn cell, motoneuron.- multipolar n. a n. with several processes, usually an axon and three or more dendrites.- NANC n. abbreviation for nonadrenergic, noncholinergic n..- nonadrenergic, noncholinergic n. (NANC n.) autonomic efferent n. whose transmission is not blocked by blocking adrenergic and cholinergic transmission. Nitric oxide may be the transmitter in some cases.- polymorphic n. occurring in many shapes. SEE ALSO: multipolar cell.- pseudounipolar n. SYN: unipolar n..- sensory n. a n. conveying information originating from sensory receptors or nerve endings; afferent n., may be general or special sensory.- unipolar n. a n. whose cell body emits a single axonal process resulting from the fusion of two polar processes during development; at a variable distance from the cell body, the process divides into a peripheral axon branch extending outward as a peripheral afferent (sensory) nerve fiber and a central axon branch that enters into synaptic contact with neurons in the spinal cord or brainstem. With the single known exception of the neurons composing the mesencephalic nucleus of the trigeminus, unipolar neurons are the exclusive neural elements of the sensory ganglia. The lack of dendritic processes of these primary sensory neurons is only apparent : the dendritic pole of the unipolar n. is represented by the unmyelinated terminal ramifications of the peripheral axon branch. SYN: pseudounipolar cell, pseudounipolar n., unipolar cell.- upper motor n. clinical term indicating those neurons of the motor cortex that contribute to the formation of the corticospinal and corticonuclear (corticobulbar) tracts, as distinguished from the lower motor neurons innervating the skeletal muscles. Although not motor neurons in the strict sense, these cortical neurons became colloquially classified as motor neurons because their stimulation produces movement and their destruction causes moderate to severe disorders of movement. SEE ALSO: motor n., motor cortex.
* * *
neu·ron 'n(y)ü-.rän, 'n(y)u̇(ə)r-.än also neu·rone -.rōn, -.ōn n one of the cells that constitute nervous tissue, that have the property of transmitting and receiving nervous impulses, and that are composed of somewhat reddish or grayish protoplasm with a large nucleus containing a conspicuous nucleolus, irregular cytoplasmic granules, and cytoplasmic processes which are highly differentiated frequently as multiple dendrites or usu. as solitary axons and which conduct impulses toward and away from the nerve cell body called also nerve cell* * *
neu·ron (noorґon) [Gr. “nerveâ€] [TA] any of the conducting cells of the nervous system. A typical neuron consists of a cell body, containing the nucleus and the surrounding cytoplasm (perikaryon); several short radiating processes (dendrites); and one long process (the axon), which terminates in twiglike branches (telodendrons) and may have branches (collaterals) projecting along its course. The axon together with its covering or sheath forms the nerve fiber. See illustration and Plate 39. Called also nerve cell. neuronal adj
Scanning electron micrograph of a neuron.
Medical dictionary. 2011.
