(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 f.A heavily myelinated, fast-conducting nerve fiber.

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

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

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

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

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

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

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

dietary f.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. The recommended minimal daily consumption of fiber is approximately 33 g/day (for men) and 28 g/day (women).

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.

SEE: insoluble fiber; soluble fiber.

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

extrafusal f.Any of the muscle fibers surrounding a muscle spindle.

fermentable f.Soluble fiber.

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

inhibitory f.A nerve fiber that carries impulses to decrease heart rate.

insoluble f.Any dietary fiber (such as wheat bran) that does not dissolve in water.

SEE: dietary fiber; soluble fiber.

intercolumnar f.Intercrural fiber

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

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

intrafusal muscle f.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 f.s

SEE: James fibers.

Mahaim f.s

SEE: Mahaim fibers.

man-made f.Synthetic fiber

medullated f.Myelinated fiber

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

Müller f.

SEE: under Müller, Heinrich.

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

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

nerve f.

SEE: nerve fiber.

nigrostriatal f.Nigrostriate bundle.

nonmedullated f.Unmyelinated fiber.

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

preganglionic f.The axon of a preganglionic neuron.

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

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

Purkinje f.

SEE: under Purkinje, Johannes E. von.

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

secretory f.A peripheral motor nerve fiber that innervates gland s and stimulates secretion.

Sharpey f.

SEE: under Sharpey, William.

Sharpey perforating f.

SEE: under Sharpey, William.

soluble f.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: fermentable fiber.

SEE: dietary fiber; insoluble fiber.

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

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

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

zonular f.Any of the interlacing fibers of the ciliary zonule.