| unipolar neuron | A neuron 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 fibre, and a central axon branch that enters into synaptic contact with neuron's in the spinal cord or brainstem. With the single known exception of the neuron's composing the mesencephalic nucleus of the trigeminus, unipolar neuron's are the exclusive neural elements of the sensory ganglia. The lack of dendritic processes of these primary sensory neuron's is only apparent: the dendritic pole of the unipolar neuron is represented by the unmyelinated terminal ramifications of the peripheral axon branch. Synonym: pseudounipolar cell, pseudounipolar neuron, unipolar cell. (05 Mar 2000) |
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| unipolar | 1. <physics> Having, or acting by means of, one pole only. 2. <anatomy> Having but one pole or process; applied to those ganglionic nerve cells which have but one radiating process; opposed to multipolar. <physics> Unipolar induction, the simulation sometimes produced when one electrode of an induction apparatus is applied to a nerve. Synonym: unipolar induction action. Origin: Uni- + polar. Source: Websters Dictionary (01 Mar 1998) |
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| unipolar arc | <radiobiology> Arc between a metal surface and a plasma in contact with it. Such an arc requires only one electrode and is maintained by the thermal energy of the electrons. (09 Oct 1997) |
| unipolar cell | A neuron 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 fibre, and a central axon branch that enters into synaptic contact with neuron's in the spinal cord or brainstem. With the single known exception of the neuron's composing the mesencephalic nucleus of the trigeminus, unipolar neuron's are the exclusive neural elements of the sensory ganglia. The lack of dendritic processes of these primary sensory neuron's is only apparent: the dendritic pole of the unipolar neuron is represented by the unmyelinated terminal ramifications of the peripheral axon branch. Synonym: pseudounipolar cell, pseudounipolar neuron, unipolar cell. (05 Mar 2000) |
| unipolar electrocardiogram | An electrocardiogram taken with the exploring electrode placed on the chest overlying the heart or upon a single limb, the indifferent ("zero" potential) electrode being the central terminal. (05 Mar 2000) |
| unipolar leads | Those in which the exploring electrode is on the chest in the vicinity of the heart or on one of the limbs, while the other or indifferent electrode is the central terminal. (05 Mar 2000) |
| autonomic motor neuron | See: motor neuron. (05 Mar 2000) |
| bipolar neuron | A neuron that has two processes arising from opposite poles of the cell body. (05 Mar 2000) |
| magnocellular neuron | <anatomy, neurology> A neuron in the magnocellular region of the brain. Perhaps the first class of neuron from the central nervous system shown to be sensitive to nerve growth factor (that had previously been thought only to act at the periphery). (18 Nov 1997) |
| ganglionic motor neuron | See: motor neuron. (05 Mar 2000) |
| Mauthner neuron | <biology, marine biology> Large neuron in the mesencephalon of fishes and amphibians. A rare example of an individually identifiable neuron in a vertebrate nervous system. (18 Nov 1997) |
| visceral motor neuron | See: motor neuron. (05 Mar 2000) |
| cell adhesion molecules, neuron-glia | Cell adhesion molecules that mediate neuron-neuron adhesion and neuron-astrocyte adhesion. They are expressed on neurons and schwann cells, but not astrocytes and are involved in neuronal migration, neurite fasciculation, and outgrowth. Ng-cam is immunologically and structurally distinct from ncam (neural cell adhesion molecules). (12 Dec 1998) |
| Golgi type II neuron | <physiology> Nerve cells with short axons which ramify in the gray matter. (05 Mar 2000) |
| Golgi type I neuron | <physiology> Nerve cells whose long axons leave the gray matter of which they form a part. (05 Mar 2000) |
| cholinergic neuron | <physiology> Neurons in which actylcholine is the neurotransmitter. (15 Jan 1998) |