| alpha fibres | Large somatic motor or proprioceptive nerve fibre's conducting impulses at rates near 100 m/sec. (05 Mar 2000) |
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| anastomosing fibres | Anastomotic fibres, individual fibre's passing from one nerve trunk or muscle bundle to another. (05 Mar 2000) |
| arcuate fibres | Nervous or tendinous fibre's passing in the form of an arch from one part to another. See: arcuate fibres of cerebrum, external arcuate fibres, internal arcuate fibres. (05 Mar 2000) |
| arcuate fibres of cerebrum | Short association fibres that connect adjacent gyri in the cerebral cortex. Synonym: fibrae arcuatae cerebri. (05 Mar 2000) |
| association fibres | Nerve fibre's interconnecting subdivisions of the cerebral cortex of the same hemisphere or different segments of the spinal cord on the same side. Synonym: endogenous fibres, intrinsic fibres. (05 Mar 2000) |
| 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) |
| 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, 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) |