| reticulospinal tract | Collective term denoting a variety of fibre tracts descending to the spinal cord from the reticular formation of the pons and medulla oblongata. Part of these fibres conduct impulses from the neural mechanisms regulating autonomic functions to the corresponding somatic and visceral motor neurons of the spinal cord; others form links in nonpyramidal motor mechanisms affecting muscle tonus, reflex activity, and somatic movement. Synonym: tractus reticulospinalis. (05 Mar 2000) |
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| Gowers' tract | A bundle of fibres originating in the base of the posterior horn and zona intermedia throughout lumbosacral segments of the spinal cord, crossing to the opposite side and ascending in a peripheral position in the ventral half of the lateral funiculus. In its ascent through the rhombencephalon, the tract curves sharply dorsalward along the rostral border of the trigeminal motor nucleus, entering the cerebellum in a caudal direction over the dorsal surface of the superior cerebellar peduncle, and terminating as mossy fibres in the granular layer of the cortex of the cerebellar vermis. The bundle conveys proprioceptive and exteroceptive information largely from the opposite lower extremity. Synonym: tractus spinocerebellaris anterior, Gowers' column, Gowers' tract, ventral spinocerebellar tract. (05 Mar 2000) |
| mesencephalic tract of trigeminal nerve | <anatomy, nerve> Located alongside the central substance of the midbrain and composed of primary sensory fibres, the cells of origin of which compose the mesencephalic nucleus of the trigeminus. Synonym: tractus mesencephalicus nervi trigemini. (05 Mar 2000) |
| granuloma, respiratory tract | Granulomatous diseases affecting one or more sites in the respiratory tract. (12 Dec 1998) |
| roots of olfactory tract | Lateral and medial, the two fibre bands that form the caudal continuation of the olfactory tract which, upon diverging, enclose the olfactory tubercle. (05 Mar 2000) |
| rubrobulbar tract | That component of the rubrospinal tract which distributes its fibres to lateral parts of the rhombencephalic tegmentum rather than the spinal cord, uncrossed rubro-olivary fibres. (05 Mar 2000) |
| rubroreticular tract | Fibres that pass from the red nucleus to the reticular formation of the pons and medulla. (05 Mar 2000) |
| rubrospinal tract | A somatotopically organised fibre bundle, relatively small in humans, arising from the red nucleus, immediately crossing in the ventral tegmental decussation, descending near the lateral surface of the brainstem into the lateral funiculus of the spinal cord at the ventral border of the lateral pyramidal tract. It terminates in the zona intermedia of the spinal cord where its distribution coincides with that of the lateral pyramidal tract; in contrast to the latter it appears not to have direct connections with spinal motor neurons. Impulses conveyed by this tract indirectly increase flexor muscle tone. Synonym: tractus rubrospinalis, Monakow's bundle, Monakow's tract, prepyramidal tract. (05 Mar 2000) |
| Waldeyer's tract | A longitudinal bundle of thin, unmyelinated and poorly myelinated fibres capping the apex of the posterior horn of the spinal gray matter, composed of posterior root fibres and short association fibres that interconnect neighboring segments of the posterior horn. Synonym: fasciculus dorsolateralis, tractus dorsolateralis, dorsolateral tract, fasciculus marginalis, Lissauer's bundle, Lissauer's column, Lissauer's fasciculus, Lissauer's marginal zone, Lissauer's tract, marginal fasciculus, Spitzka's marginal tract, Spitzka's marginal zone, Waldeyer's tract, Waldeyer's zonal layer. (05 Mar 2000) |
| Monakow's tract | A somatotopically organised fibre bundle, relatively small in humans, arising from the red nucleus, immediately crossing in the ventral tegmental decussation, descending near the lateral surface of the brainstem into the lateral funiculus of the spinal cord at the ventral border of the lateral pyramidal tract. It terminates in the zona intermedia of the spinal cord where its distribution coincides with that of the lateral pyramidal tract; in contrast to the latter it appears not to have direct connections with spinal motor neurons. Impulses conveyed by this tract indirectly increase flexor muscle tone. Synonym: tractus rubrospinalis, Monakow's bundle, Monakow's tract, prepyramidal tract. (05 Mar 2000) |
| Collier's tract | A longitudinal bundle of fibres extending from the upper border of the mesencephalon into the cervical segments of the spinal cord, located close to the midline and ventral to the central gray matter; it is composed largely of fibres from the vestibular nuclei ascending to the motor neurons innervating the external eye muscles (abducens, trochlear, and oculomotor nuclei), and descending to spinal cord segments innervating the musculature of the neck. Synonym: fasciculus longitudinalis medialis, Collier's tract, medial longitudinal bundle, posterior longitudinal bundle. (05 Mar 2000) |
| comma tract of Schultze | A compact bundle composed of descending branches of posterior root fibres located near the border between the fasciculi gracilis and cuneatus of the cervical and thoracic spinal cord; it corresponds to the septomarginal fasciculus, Hoche's tract, or oval area of Flechsig in the lumbar, and to the triangle of Philippe-Gombault in the sacral spinal segments; like these, it can be demonstrated only in cases of demyelination resulting from dorsal root lesions. Synonym: fasciculus semilunaris, fasciculus interfascicularis, comma bundle of Schultze, comma tract of Schultze, interfascicular fasciculus. (05 Mar 2000) |
| corticobulbar tract | <physiology> Collective term for those fibres (corticonuclear fibres) which separate from the corticospinal tract in the course of the latter's descent through the pons and medulla oblongata. Fibres of this tract innervate the motor nuclei of the trigeminal, facial, and hypoglossal nerves (perhaps also the nucleus ambiguus), directly and by way of interneurons in the lateral part of the rhombencephalic tegmentum. No direct supranuclear cortical innervation of the motor nuclei innervating the external eye muscles (oculomotor, trochlear, abducens) has been identified. Fibres of the corticobulbar tract also project into the formatio reticularis (i.e., corticoreticular fibres) and terminate upon sensory relay nuclei (e.g., gracile and cuneate nuclei, nucleus spinalis trigeminalis and nucleus solitarius). Synonym: tractus corticobulbaris. (05 Mar 2000) |
| corticopontine tract | <anatomy, physiology> Collective term for the multitude of fibres which, originating in all of the major subdivisions of the cerebral cortex, descend in the internal capsule and crus cerebri to terminate in the nuclei of the ventral part of the pons. Individual components of this massive fibre system are indicated, according to their origin in the cerebral cortex, as the frontopontine tract, parietopontine tract, occipitopontine tract, and temporopontine tract. Synonym: tractus corticopontini. (05 Mar 2000) |
| corticospinal tract | A massive bundle of fibres originating from pyramidal cells of various sizes in the fifth layer of the precentral motor (area 4), the premotor area (area 6), and to a lesser extent from the postcentral gyrus. Cells of origin in area 4 include the gigantopyramidal cells of Betz. Fibres from these cortical regions descend through the internal capsule, the middle third of the crus cerebri, and the ventral part of the pons to emerge on the ventral surface of the medulla oblongata as the pyramis. Continuing caudally, most of the fibres cross to the opposite side in the pyramidal decussation and descend in the dorsal half of the lateral funiculus of the spinal cord as the lateral pyramidal tract, which distributes its fibres throughout the length of the spinal cord to interneurons of the zona intermedia of the spinal gray matter. In the (extremity-related) spinal cord enlargements, fibres also pass directly to motoneuronal groups that innervate distal extremity muscles subserving particular hand-and-finger or foot-and-toe movements. The uncrossed fibres form a small bundle, the anterior pyramidal tract, which descends in the anterior funiculus of the spinal cord and terminates in synaptic contact with interneurons in the medial half of the anterior horn on both sides of the spinal cord. Interruption of the pyramidal tract at or below its cortical origin causes impairment of movement in the opposite body-half, especially severe in the arm and leg; characterised by muscular weakness, spasticity and hyperreflexia, and a loss of discrete finger and hand movements. Babinski's sign is associated with this condition of hemiplegia. Synonym: tractus corticospinalis, tractus pyramidalis, corticospinal tract. (05 Mar 2000) |