| 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) |
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| 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) |
| triangular nucleus | Alternative term for the medial vestibular nucleus. (05 Mar 2000) |
| trigeminal caudal nucleus | The caudal portion of the nucleus of the spinal trigeminal tract (trigeminal nucleus, spinal), a nucleus involved with pain and temperature sensation. (12 Dec 1998) |
| trigeminal nucleus, spinal | Nucleus of the spinal tract of the trigeminal nerve. It is divided cytoarchitectonically into three parts: oralis, caudalis (trigeminal caudal nucleus), and interpolaris. (12 Dec 1998) |
| trochlear nucleus | A group of motor neurons innervating the superior oblique muscle of the contralateral eye. The nucleus lies in the caudal half of the midbrain, behind the oculomotor nucleus, in the most ventral part of the central gray substance, near the midline. Synonym: nucleus nervi trochlearis, nucleus of trochlear nerve. (05 Mar 2000) |
| trophic nucleus | The larger nucleus (or sometimes nuclei) in ciliate protozoans. Derived from the micronucleus by a process of DNA polytenisation. The DNA in the macronucleus is actively transcribed. The macronucleus degenerates before conjugation. (18 Nov 1997) |
| tubercle of nucleus gracilis | tubercle of gracile nucleus |
| external cuneate nucleus | A cell group lateral to the cuneate nucleus which receives posterior-root fibres corresponding to the proprioceptive innervation of the arm and hand; it projects to the cerebellum by way of the cuneocerebellar tract, and can be considered the upper-extremity equivalent of the thoracic nucleus. Synonym: nucleus cuneatus accessorius, external cuneate nucleus, lateral cuneate nucleus, Monakow's nucleus. (05 Mar 2000) |