| nucleus of oculomotor nerve | 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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| nucleus of solitary tract | A slender cell column extending sagittally through the dorsal part of the medulla oblongata, beneath the floor of the rhomboid fossa, immediately lateral to the limiting sulcus. It is the visceral sensory (visceral afferent) nucleus of the brainstem, receiving the afferent fibres of the vagus, glossopharyngeal, and facial nerves by way of the solitary tract. The caudal two-thirds of the nucleus processes impulses originating in the pharynx, larynx, intestinal and respiratory tracts, and heart and large blood vessels; its rostral one-third receives impulses from the taste buds and is known as the rhombencephalic gustatory nucleus. Synonym: nucleus tractus solitarii. (05 Mar 2000) |
| nucleus of the mamillary body | A single large-celled lateral nucleus and a larger bipartite medial nucleus together comprising the mamillary body; present in the caudal hypothalamus. Synonym: nuclei corporis mamillaris, nucleus of the mamillary body. (05 Mar 2000) |
| nucleus of trochlear nerve | 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) |
| nucleus olivaris | A large aggregate of small densely packed nerve cells arranged in folded laminae shaped like a purse with the opening (hilum) directed medially. It corresponds in position to the oliva, projects to all parts of the contralateral half of the cerebellar cortex by way of the olivocerebellar tract, and is the only source of cerebellar climbing fibres. Its afferent connections include fibres from the spinal cord, the dentate nucleus and motor cortex, but its major input appears to be the central tegmental tract originating from multiple nuclei at midbrain levels. Synonym: nucleus olivaris. (05 Mar 2000) |
| nucleus olivaris accessorius dorsalis | A detached part of the olivary nucleus dorsal to the latter's main body. Synonym: nucleus olivaris accessorius dorsalis. (05 Mar 2000) |
| nucleus olivaris accessorius medialis | A detached part of the olivary nucleus medial to the latter's main body, against the lateral side of the medial lemniscus and pyramidal tract. Synonym: nucleus olivaris accessorius medialis. (05 Mar 2000) |
| nucleus paracentralis thalami | One of the intralaminar nuclei of the thalamus, medial to the central lateral nucleus. Synonym: nucleus paracentralis thalami. (05 Mar 2000) |
| nucleus paraventricularis | A triangular group of large magnocellular neurons in the periventricular zone of the anterior half of the hypothalamus. The cells of the nucleus are similar to those of the supraoptic nucleus; the axons of about 20% of their number join in the formation of the supraopticohypophysial tract and are functionally associated with the posterior lobe of the hypophysis; they project fibres to the brainstem nuclei (dorsal motor nucleus and solitary nucleus) and to the intermediolateral cell column of the spinal cord at thoracic, lumbar, and spinal levels; similar descending autonomic fibres arise from the lateral and posterior hypothalamic nuclei. Synonym: nucleus paraventricularis, filiform nucleus, nucleus filiformis. (05 Mar 2000) |
| nucleus preopticus lateralis | A vaguely defined group of nerve cells in the lateral zone of the preoptic region. Synonym: nucleus preopticus lateralis. (05 Mar 2000) |
| nucleus preopticus medialis | A group of nerve cells forming the medial zone of the preoptic region. Synonym: nucleus preopticus medialis. (05 Mar 2000) |
| nucleus pulposus | The soft fibrocartilage central portion of the intervertebral disk; regarded as a derivative of the notochord. Synonym: gelatinous nucleus, nucleus gelatinosus, vertebral pulp. (05 Mar 2000) |
| nucleus pyramidalis | An obsolete term for nucleus olivaris accessorius medialis. (05 Mar 2000) |
| nucleus reticularis thalami | A sheet of fairly large neurons covering the lateral, ventral, and rostral surfaces of the thalamus; its reticular appearance is caused by the numerous fascicles of the thalamic peduncles which traverse the nucleus The nucleus receives numerous fibres from the cerebral cortex but it has no cortical projection. Synonym: nucleus reticularis thalami. (05 Mar 2000) |
| nucleus ruber | A distinctive oval nucleus (pink in fresh specimens because of an iron-containing pigment in many of the cells) centrally placed in the upper mesencephalic reticular formation. It receives fibres from the deep cerebellar nuclei and cerebral cortex and projects fibres to the cerebellum, brainstem, spinal cord, and probably to the thalamus. The nucleus is divided into two regions: pars magnocellularis and pars parvocellularis. (12 Dec 1998) |