association fiber

fiber /fi·ber/ (fi´ber)

1. an elongated, threadlike structure.

2. nerve f.

3. dietary f.

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A fibers  myelinated afferent or efferent fibers of the somatic nervous system having a diameter of 1 to 22 μm and a conduction velocity of 5 to 120 meters per second; they include the alpha, beta, delta, and gamma fibers.

accelerating fibers , accelerator fibers adrenergic fibers that transmit the impulses which accelerate the heart beat.

adrenergic fibers  nerve fibers, usually sympathetic, that liberate epinephrine or related substances as neurotransmitters.

afferent fibers , afferent nerve fibers nerve fibers that convey sensory impulses from the periphery to the central nervous system.

alpha fibers  motor and proprioceptive fibers of the A type, having conduction velocities of 70 to 120 meters per second and ranging from 13 to 22 μm in diameter.

alveolar fibers  fibers of the periodontal ligament extending from the cementum of the tooth root to the walls of the alveolus.

arcuate fibers  the bow-shaped fibers in the brain, such as those connecting adjacent gyri in the cerebral cortex, or the external or internal arcuate fibers of the medulla oblongata.

association fiber  one of the nerve fibers connecting different cortical areas within one hemisphere.

autonomic nerve fibers  nerve fibers that innervate smooth muscle and glandular tissues, either stimulating and activating the muscle or tissue (autonomic efferent f's) or receiving sensory impulses from them (autonomic afferent f's) .

B fibers  myelinated preganglionic autonomic axons having a fiber diameter of ≤ 3 μm and a conduction velocity of 3 to 15 meters per second; these include only efferent fibers.

basilar fibers  those that form the middle layer of the zona arcuata and the zona pectinata of the organ of Corti.

beta fibers  motor and proprioceptive fibers of the A type, having conduction velocities of 30 to 70 meters per second and ranging from 8 to 13 μm in diameter.

C fibers  unmyelinated postganglionic fibers of the autonomic nervous system, also the unmyelinated fibers at the dorsal roots and at free nerve endings, having a conduction velocity of 0.6 to 2.3 meters per second and a diameter of 0.3 to 1.3 μm.

collagen fibers , collagenous fibers the soft, flexible, white fibers which are the most characteristic constituent of all types of connective tissue, consisting of the protein collagen, and composed of bundles of fibrils that are in turn made up of smaller units (microfibrils), which show a characteristic crossbanding with a major periodicity of 65 nm.

commissural fiber  one of the nerve fibers which pass between the cortex of opposite hemispheres of the brain, or between two sides of the brain stem or spinal cord.

dietary fiber  that part of whole grains, vegetables, fruits, and nuts that resists digestion in the gastrointestinal tract; it consists of carbohydrate (cellulose, etc.) and lignin.

efferent fibers , efferent nerve fibers nerve fibers that convey motor impulses away from the central nervous system toward the periphery.

elastic fibers  yellowish fibers of elastic quality traversing the intercellular substance of connective tissue.

fusimotor fibers  efferent A fibers that innervate the intrafusal fibers of the muscle spindle.

gamma fibers  any A fibers that conduct at velocities of 15 to 40 meters per second and range from 3 to 7 μm in diameter, comprising the fusimotor fibers.

gray fibers  unmyelinated nerve fibers found largely in the sympathetic nerves.

insoluble fiber  that not soluble in water, composed mainly of lignin, cellulose, and hemicelluloses and primarily found in the bran layers of cereal grains.

intrafusal fibers  modified muscle fibers which, surrounded by fluid and enclosed in a connective tissue envelope, compose the muscle spindle.

Mahaim fibers  specialized tissue connecting components of the conduction system directly to the ventricular septum.

motor fibers  efferent fibers.

Müller's fibers  elongated neuroglial cells traversing all the layers of the retina, forming its principal supporting element.

muscle fiber  any of the cells of skeletal or cardiac muscle tissue. Skeletal muscle fibers are cylindrical multinucleate cells containing contracting myofibrils, across which run transverse striations. Cardiac muscle fibers have one or sometimes two nuclei, contain myofibrils, and are separated from one another by an intercalated disk; although striated, cardiac muscle fibers branch to form an interlacing network.

myelinated fibers  grayish white nerve fibers whose axons are encased in a myelin sheath, which may in turn be enclosed by a neurilemma.

nerve fiber  a slender process of a neuron, especially the prolonged axon which conducts nerve impulses away from the cell; classified as either afferent or efferent according to the direction the impulses flow, and either myelinated or unmyelinated according to whether there is or is not a myelin sheath.

osteogenetic fibers , osteogenic fibers precollagenous fibers formed by osteoclasts and becoming the fibrous component of bone matrix.

preganglionic fibers  the axons of preganglionic neurons.

pressor fibers  nerve fibers which, when stimulated reflexly, cause or increase vasomotor tone.

projection fiber , projection nerve fibers one of the nerve fibers that connect the cerebral cortex with the subcortical centers, the brain stem, and the spinal cord.

Purkinje fibers  modified cardiac muscle fibers composed of Purkinje cells, occurring as an interlaced network in the subendothelial tissue and constituting the terminal ramifications of the cardiac conducting system.

radicular fibers  fibers in the roots of the spinal nerves.

reticular fibers  immature connective tissue fibers staining with silver, forming the reticular framework of lymphoid and myeloid tissue, and occurring in interstitial tissue of glandular organs, the papillary layer of the dermis, and elsewhere.

sensory fibers  afferent fibers.

Sharpey's fibers 

1. collagenous fibers that pass from the periosteum and are embedded in the outer circumferential and interstitial lamellae of bone.

2. terminal portions of principal fibers that insert into the cementum of a tooth.

soluble fiber  that with an affinity for water, either dissolving or swelling to form a gel; it includes gums, pectins, mucilages, and some hemicelluloses, and is primarily found in fruits, vegetables, oats, barley, legumes, and seaweed.

somatic nerve fibers  nerve fibers that stimulate and activate skeletal muscle and somatic tissues (somatic efferent f's) or receive impulses from them (somatic afferent f's) .

spindle fibers  the microtubules radiating from the centrioles during mitosis and forming a spindle-shaped configuration.

traction fibers  spindle f's.

unmyelinated fibers  nerve fibers that lack the myelin sheath.

vasomotor fibers  unmyelinated nerve fibers going chiefly to arteriolar muscles.

visceral nerve fibers  autonomic nerve f's.

white fibers  collagenous f's.

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association fiber

n.

Any of the nerve fibers connecting individual subdivisions of a brain structure or different segments of the spinal cord.