| intercalated nucleus | A small collection of nerve cells in the medulla oblongata lying lateral to the hypoglossal nucleus. Synonym: nucleus intercalatus, Staderini's nucleus. (05 Mar 2000) |
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| intermediolateral nucleus | The cell column that forms the lateral horn of the spinal cord's gray matter. Extending from the first thoracic through the second lumbar segment, the column contains the autonomic motor neurons that give rise to the preganglionic fibres of the sympathetic system. Synonym: intermediolateral cell column of spinal cord, nucleus intermediolateralis. (05 Mar 2000) |
| intermediomedial nucleus | A small group of scattered visceral motor neurons immediately ventral to the thoracic nucleus in the thoracic and upper two lumbar segments of the spinal cord; considered to receive visceral afferent fibres at all spinal levels. Synonym: nucleus intermediomedialis. (05 Mar 2000) |
| interpeduncular nucleus | A median, unpaired, ovoid cell group at the base of the midbrain tegmentum between the cerebral peduncles; it receives the retroflex fasciculus from the habenula, and projects to the raphe region (raphe nuclei) and periaqueductal gray substance of the midbrain. Synonym: nucleus interpeduncularis, ganglion isthmi, Gudden's ganglion, intercrural ganglion, interpeduncular ganglion. (05 Mar 2000) |
| interpositus nucleus | Collective term denoting the combined globosus nuclei and emboliform nuclei of the cerebellum; more correctly used as interposed nuclei as it identifies two cell groups. Synonym: nucleus interpositus. (05 Mar 2000) |
| interstitial nucleus | A group of widely spaced, medium-sized neurons in the dorsomedial region of the upper mesencephalic tegmentum, immediately lateral to the nucleus of Darkschewitsch; together with the latter, the interstitial nucleus is closely associated with the medial longitudinal fasciculus, via which it receives fibres from the vestibular nuclei and projects crossed fibres via the posterior commissure to the oculomotor nucleus; also projects fibres to all spinal levels. It is believed to be involved in the integration of head and eye movements, particularly eye movements of a vertical or oblique nature. Synonym: nucleus interstitialis, interstitial nucleus of Cajal. (05 Mar 2000) |
| interstitial nucleus of Cajal | A group of widely spaced, medium-sized neurons in the dorsomedial region of the upper mesencephalic tegmentum, immediately lateral to the nucleus of Darkschewitsch; together with the latter, the interstitial nucleus is closely associated with the medial longitudinal fasciculus, via which it receives fibres from the vestibular nuclei and projects crossed fibres via the posterior commissure to the oculomotor nucleus; also projects fibres to all spinal levels. It is believed to be involved in the integration of head and eye movements, particularly eye movements of a vertical or oblique nature. Synonym: nucleus interstitialis, interstitial nucleus of Cajal. (05 Mar 2000) |
| oculomotor nucleus | The composite group of motor neurons innervating all of the external eye muscles except the musculus rectus lateralis and musculus obliquus superior, and including the musculus levator palpebrae superioris; the most rostral component of the nucleus is the Edinger-Westphal nucleus which innervates the musculi sphincter pupillae and ciliaris via the ciliary ganglion. The oculomotor nucleus lies in the rostral half of the midbrain, near the midline in the most ventral part of the central gray substance; fibres of the medial longitudinal fasciculus form its lateral borders. Synonym: nucleus nervi oculomotorii, nucleus of oculomotor nerve. (05 Mar 2000) |
| Onuf's nucleus | Small somatic motor neurons in the ventral horn of the spinal cord at sacral 2 level which innervate the vesicorectal sphincters, that is, the external anal and the urethral sphincter; O.'s nucleus has been identified in the cat, dog, and humans. (05 Mar 2000) |
| tail of caudate nucleus | The elongated posterior extension of the caudate nucleus that parallels the body and inferior horn of the lateral ventricle. Synonym: cauda nuclei caudati, cauda striati. (05 Mar 2000) |
| tectal nucleus | The most medial of the cerebellar nuclei, lying medial to the interpositus nucleus, near the midline, in the white matter underneath the vermis of the cerebellar cortex. It receives the axons of Purkinje cells from all parts of the vermis. Its major projection is to the vestibular nuclei and medullary reticular formation. Synonym: nucleus fastigii, fastigatum, nucleus tecti, roof nucleus, tectal nucleus. (05 Mar 2000) |
| thalamic gustatory nucleus | The small ventral region of the ventral posteromedial nucleus of thalamus in which the fibres of the gustatory lemniscus and secondary trigeminal tracts terminate; it projects to the lower part of the postcentral gyrus of the cerebral cortex. Synonym: arcuate nucleus, nucleus arcuatus thalami, nucleus arcuatus, semilunar nucleus of Flechsig, thalamic gustatory nucleus. (05 Mar 2000) |
| thoracic nucleus | A column of large neurons located in the base of the posterior gray column of the spinal cord, extending from the first thoracic through the second lumbar segment; it gives rise to the dorsal spinocerebellar tract of the same side. Synonym: nucleus thoracicus, Clarke's column, Clarke's nucleus, dorsal nucleus, nucleus dorsalis, Stilling's column, Stilling's nucleus. (05 Mar 2000) |
| Edinger-Westphal nucleus | A small group of preganglionic parasympathetic motor neurons in the midline near the rostral pole of the oculomotor nucleus of the midbrain; the axons of these motor neurons leave the brain with the oculomotor nerve and synapse on the cells of the ciliary ganglion which in turn innervate the sphincter muscle of the pupil and ciliary muscle. Destruction of this nucleus or its efferent fibres causes maximal paralytic dilation of the pupil; also demonstrated to project fibres to lower levels of the brainstem and all spinal levels. (05 Mar 2000) |
| emboliform nucleus | A small wedge-shaped nucleus in the central white substance of the cerebellum just internal to the hilus of the dentate nucleus; receives axons of Purkinje cells of the intermediate area of the cerebellar cortex; axons of these cells exit the cerebellum via the superior cerebellar peduncle. Synonym: nucleus emboliformis, embolus. (05 Mar 2000) |