nerve

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nerve:

see 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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Nerve

 

the cordlike association of nerve tissues that links the brain and nerve ganglia by innervation to the other organs and tissues of the body.

A nerve primarily consists of nerve fibers. In vertebrates many nerves converge to form a bundle that is surrounded by a connective tissue sheath, the perineurium; the thin interstitial layers of connective tissue that separate the individual fibers deep within the bundle constitute the endoneurium. Finally, the entire nerve trunk, comprising several bundles, is covered by an additional sheath, the epineurium.

Nerves can be sensory (also called afferent or centripetal) or motor (also called efferent or centrifugal). Some nerves, for example, those innervating the skeletal muscles, mainly include myelinated, or medullated, fibers; others, for example, the sympathetic nerves, largely consist of unmyelinated, or unmedullated, fibers.

In reptiles, birds, mammals, and man 12 pairs of cranial nerves branch from the brain: the olfactory (cranial nerve I), the optic (cranial nerve II), the oculomotor (cranial nerve III), the trochlear (cranial nerve IV), the trigeminal (cranial nerve V), the abducent (cranial nerve VI), the facial (cranial nerve VII), the acoustic (cranial nerve VIII), the glossopharyngeal (cranial nerve IX), the vagus (cranial nerve X), the accessory (cranial nerve XI), and the hypoglossal (cranial nerve XII). Only the first ten pairs are present in fish and amphibians.

In man there are 31 pairs of spinal nerves: eight cervical, 12 thoracic, five lumbar, five sacral, and one coccygeal. Each pair innervates the effectors and receptors of a certain part of the body. The spinal nerves branch from the spinal cord into two roots—the posterior, or sensory, and the anterior, or motor. Both roots then combine to form a common trunk that consists of both sensory and motor fibers.

Several adjacent nerves can be combined into nerve plexuses, where an exchange of fibers between different nerves can take place. Three large plexuses are distinguished: the cervical, the brachial, and the lumbosacral. Each nerve plexus is the origin of several pairs of nerves; for example, the sacral portion of the lumbosacral plexus gives rise to the sciatic nerves.

Nerves that originate in the ganglia, trunks, and plexuses of the autonomic nervous system constitute a specific group. The optic nerve is remarkable for its large number of fibers; there are more than 1 million in the human optic nerve. Usually, however, there are 103 -104 fibers in a nerve. In invertebrates certain nerves are known to consist of only a few fibers. The peripheral nervous system in animals and man consists of aggregations of nerves.

D. A. SAKHAROV

nerve

[nərv]
(neuroscience)
A bundle of nerve fibers or processes held together by connective tissue.

nervure

Any one of the ribs of a groined vault, but esp. a rib which forms one of the sides of a compartment of the groining.

nerve

1. any of the cordlike bundles of fibres that conduct sensory or motor impulses between the brain or spinal cord and another part of the body
2. a large vein in a leaf
3. any of the veins of an insect's wing
References in periodicals archive ?
Relapse will be defined by the presence of new signs and symptoms or new finding of AFBs in skin or nerve biopsy.
Seven of 11 VN patients had superficial peroneal nerve biopsy with peroneus brevis muscle biopsy whereas four patients had sural nerve biopsy All biopsies were snap-frozen within 5 min of surgical intervention and stored at -80[degrees]C until analysis.
While the normal morphology in the sural nerve biopsy with electron mycroscope in patients with congenital indifference to pain rules out the selective absence of unmyelinated nociceptors, this exam does not rule out the possibility of other chemical or structural abnormalities, for example, alterations in neurotransmitters or in central sensory pathways (2).
Round or ovoid basophilic inclusions identical to those in the nerve biopsy were seen in myoepithelial cells of the apocrine coils, often indenting the nucleus in a characteristic fashion (Figure 2, A).
3%) were treated with multi drug therapy-multibacillary (MDT-MB) regimen ([greater than or equal to] 2 peripheral nerve trunks involved or demonstrable acid-fast bacilli, AFB in affected nerve trunk(s) on nerve biopsy or fine needle aspiration cytology, FNAC) and three (6.
The presence and degree of nerve involvement is usually evaluated by clinical assessment and by nerve biopsy at times when there is isolated nerve involvement.
Diagnostic nerve biopsy is often required, which is an invasive procedure and may lead to complications.
Histological evidence of relapse in skin or nerve biopsy f.
PATHOLOGY: Sural nerve biopsy shows a marked reduction in nerve size and depletion of large and small myelinated fibers but only a slightly decreased number of unmyelinated fibers as in our case.