(fī′bĕr)

[L. fibra, filament, fiber]

1. A threadlike or filmlike structure, e.g., a nerve fiber.
2. A neuron or its axonal portion.
3. An elongated threadlike structure. It may be cellular, like a nerve or muscle fiber, or it may be a cellular product, such as collagen, elastic, oxytalan, or reticular fiber.
4. A slender cellulosic structure derived from plants such as cotton.
SEE: purified rayon

A fiber

A heavily myelinated, fast-conducting nerve fiber.

accelerator fiber

A sympathetic nerve fiber that carries impulses to increase heart rate.

afferent fiber

A nerve fiber that carries sensory impulses to the central nervous system from receptors in the periphery.

cholinergic fiber

Any of the preganglionic, postganglionic, parasympathetic, or postganglionic sympathetic fibers to a sweat gland or efferent fibers to skeletal muscle.

circular fiber

Any of the collagen bundles in the gingiva surrounding a tooth.

climbing fiber

An excitatory axon from the inferior olivary nucleus that synapses with dendrites of Purkinje cells in the cerebellar cortex.

climbing fiber of the cerebellum

1. An afferent nerve fiber entering the cortex and synapsing with dendrites of Purkinje cells.
2. Any of the collateral branches of Purkinje cell axons that return to the molecular layer terminating about Purkinje or basket cell dendrites.

depressor fiber

1. A nerve that decreases arterial muscle tone and thereby lowers blood pressure.
2. A pressure-sensitive nerve fiber.

dietary fiber

The components of food that resist chemical digestion. These fibers are classified according to their solubility in water. Foods rich in fiber include whole-grain foods, bran flakes, beans, fruits, leafy vegetables, nuts, and root vegetables and their skins.
Water-insoluble fibers include cellulose, lignin, gums, mucilages, pectin, and some hemicelluloses. These fibers can soften and increase the bulk of the bowel movement. Most foods of plant origin contain both soluble and insoluble dietary fiber.

Water-soluble fibers are natural gel-forming fibers found in fruits and vegetables such as gums, mucilages, and some hemicelluloses.

Many disease processes including constipation, diabetes mellitus, gallstones, hemorrhoids, high blood pressure, irritable bowel syndrome, and obesity have been shown to be ameliorated by a high-fiber diet. Epidemiological data support the existence of an inverse relationship between these diseases and dietary fiber consumption. The relationship between fiber intake and colorectal cancer is complex; some studies suggest that fiber intake is protective; others suggest that it is not.

SEE: insoluble fiber; SEE: soluble fiber

efferent fiber

A nerve fiber that carries motor impulses away from the central nervous system to peripheral effectors.

extrafusal fiber

Any of the muscle fibers surrounding a muscle spindle.

fermentable fiber

SEE: Soluble fiber.

gingival fiber

Any of the collagen fibers that support the marginal or interdental gingiva and are adapted to the tooth surface.

inhibitory fiber

A nerve fiber that carries impulses to decrease heart rate.

insoluble fiber

Any dietary fiber (such as wheat bran) that does not dissolve in water.
SEE: dietary fiber; SEE: soluble fiber

intercolumnar fiber

SEE: Intercrural fiber

intercrural fiber

Any of the muscle fibers that join the medial and lateral crura of the superficial inguinal ring.
SYN: SEE: intercolumnar fiber

interradicular fiber

Any of the collagen fibers of the periodontal ligament in the interradicular area, attaching the tooth to alveolar bone.

intrafusal muscle fiber

The structural component of the muscle spindle, made up of small skeletal muscle fibers at either end and a central noncontracile region where the sensory receptors are located.

James fibers

SEE: James fibers

Mahaim fibers

SEE: Mahaim fibers

man-made fiber

SEE: Synthetic fiber

medullated fiber

SEE: Myelinated fiber

mossy fiber

An excitatory axon from outside the cerebellum that synapses in the granular layer of the cerebellar cortex. Mossy fiber terminals are the central elements in complex synaptic formations that include dendrites of granular neurons and neurites of Golgi cells.

motor fiber

Any of the axons of motor neurons that innervate skeletal muscles.

Müller fiber

SEE: Müller, Heinrich

muscle fiber

A muscle cell in striated, smooth, or cardiac muscle.

myelinated fiber

A nerve fiber whose axon is wrapped in a myelin sheath.
SYN: SEE: medullated fiber

nerve fiber

SEE: nerve fiber

nigrostriatal fiber

SEE: Nigrostriate bundle.

nonmedullated fiber

SEE: Unmyelinated fiber.

oxytalan fiber

Any of the bundles of thin, acid-resistant fibrils found in the periodontium.

preganglionic fiber

The axon of a preganglionic neuron.

principal fiber

Any of the major fiber groups of the functioning periodontium that attach the tooth to the bone and adjacent teeth.

propriospinal fiber

Any of the axons that connect regions of the spinal cord.

Purkinje fiber

SEE: Purkinje, Johannes E. von

reticular fiber

Any of the extremely fine argyrophilic (silver-staining) fibers found in reticular tissue.

secretory fiber

A peripheral motor nerve fiber that innervates glands and stimulates secretion.

Sharpey fiber

SEE: Sharpey, William

Sharpey perforating fiber

SEE: Sharpey, William

soluble fiber

Any dietary fiber that dissolves in water. Soluble fiber is metabolized by bacteria in the gastrointestinal tract into short-chain fatty acids, which in turn nourish commensal bacteria in the gut. Examples include most fruit and vegetable fibers, e.g., pectins, barley, cereal grains, cornmeal, and oats.
SYN: SEE: fermentable fiber
SEE: dietary fiber; SEE: insoluble fiber

synthetic fiber

A fiber (such as rayon or polyester) manufactured from chemicals.
SYN: SEE: man-made fiber

transseptal fiber

Any of the collagenous fibers that extend between the teeth and are embedded in the cementum of adjacent teeth.

unmyelinated fiber

A nerve fiber that lacks a myelin sheath, although a neurilemma may be present in the peripheral nervous system.
SYN: SEE: nonmedullated fiber

zonular fiber

Any of the interlacing fibers of the ciliary zonule.

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