| astral fibres | Fibre's (fibrils) radiating from the centrosphere toward the periphery of the cell as seen with a light microscope; revealed as microtubules under the electron microscope. Compare: kinetochore fibres, polar fibres. (05 Mar 2000) |
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| augmentor fibres | Postganglionic sympathetic nerve fibre's originating in the superior, middle, and inferior cervical ganglia of the sympathetic trunk, conveying nervous impulses to the heart that increase the rapidity and force of the cardiac pulsations. Synonym: augmentor fibres. (05 Mar 2000) |
| autonomic fibres, postganglionic | Nerve fibres which project from cell bodies of autonomic ganglia to synapses on target organs. (12 Dec 1998) |
| autonomic fibres, preganglionic | Nerve fibres which project from the central nervous system to autonomic ganglia. In the sympathetic division most preganglionic fibres originate with neurons in the intermediolateral column of the spinal cord, exit via ventral roots from upper thoracic through lower lumbar segments, and project to the paravertebral ganglia; there they either terminate in synapses or continue through the splanchnic nerves to the prevertebral ganglia. In the parasympathetic division the fibres originate in neurons of the brainstem and sacral spinal cord. In both divisions the principal transmitter is acetylcholine but peptide cotransmitters may also be released. (12 Dec 1998) |
| Bergmann's fibres | Filamentous glia fibre's traversing the cerebellar cortex perpendicular to the surface. (05 Mar 2000) |
| beta fibres | Nerve fibre's having conduction velocities of about 40 m/sec. (05 Mar 2000) |
| B fibres | Myelinated fibre's autonomic nerves, with a diameter of 2 um or less, conducting at a rate of 3 to 15 m/sec. (05 Mar 2000) |
| gamma fibres | Nerve fibre's that have a conduction rate of about 20 m/sec. See: gamma efferent. (05 Mar 2000) |
| Mahaim fibres | Paraspecific fibre's originating from the A-V node, the His bundle, or the bundle branches and inserting into the ventricular myocardium; they are potential pathways for reentrant dysrhythmias. Synonym: nodoventricular fibres. (05 Mar 2000) |
| vasomotor fibres | Postganglionic visceral efferent fibres innervating the smooth muscles of vessel walls. (05 Mar 2000) |
| raphespinal fibres | Nerve fibres originating from cells of the nuclei raphe magnus, pallidus, and obscurus of the pons and medulla and terminating in the spinal cord gray matter; fibres involved in the descending inhibition of nociceptive input in the dorsal (posterior) horn; they contain serotonin. (05 Mar 2000) |
| parasympathetic fibres, postganglionic | Nerve fibres which project from parasympathetic ganglia to synapses on target organs. Parasympathetic postganglionic fibres use acetylcholine as transmitter. They may also release peptide cotransmitters. (12 Dec 1998) |
| Gerdy's fibres | <anatomy> A thickening of the deep fascia in the most distal part of the (base) of the triangular palmar aponeurosis. Synonym: ligamentum metacarpale transversum superficiale, Gerdy's fibres, ligamentum natatorium. (05 Mar 2000) |
| red fibres | Red striated muscle fibre's that are rich in sarcoplasm, myoglobin, and mitochondria; they are smaller in diameter and contract more slowly than white fibre's. (05 Mar 2000) |
| Remak's fibres | A fibre having no myelin covering (CNS); a naked axon; in the PNS represented by all axons lying in troughs in a single Schwann cell (Schwann cell unit); a slow conducting fibre. Synonym: gray fibres, nonmedullated fibres, Remak's fibres. (05 Mar 2000) |