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1. In cytology, typically a rounded or oval mass of protoplasm within the cytoplasm of a plant or animal cell; it is surrounded by a nuclear envelope, which encloses euchromatin, heterochromatin, and one or more nucleoli and undergoes mitosis during cell division. SYN: karyon. 2. By extension, because of similar function, the genome of microorganisms (microbes), which is relatively simple in structure, lacks a nuclear membrane and does not undergo mitosis during replication. SYN: nucleoid (3). SEE ALSO: virion. 3. [TA] In neuroanatomy, a group of nerve cell bodies in the brain or spinal cord that can be demarcated from neighboring groups on the basis of either differences in cell type or the presence of a surrounding zone of nerve fibers or cell-poor neuropil. 4. Any substance ( e.g., foreign body, mucus, crystal) around which a urinary or other calculus is formed. 5. The central portion of an atom (composed of protons and neutrons) where most of the mass and all of the positive charge are concentrated. 6. A particle on which a crystal, droplet, or bubble forms. 7. A characteristic arrangement of atoms in a series of molecules; e.g., the benzene n. is a series of aromatic compounds. [L. a little nut, the kernel, stone of fruits, the inside of a thing, dim. of nux, nut]
- abducens n., n. abducentis, n. of abducens nerve a group of motor neurons in the lower part of the pons, innervating the ipsilateral lateral rectus muscle of the eye; unique among motor cranial nerve nuclei in that it consists of two distinct populations of neurons: neurons that give rise to fibers forming the abducens nerve root and those internuclear neurons whose processes cross the midline, ascend in the opposite medial longitudinal fasciculus, and terminate upon specific oculomotor neurons; considered a primary center for mechanisms controlling conjugate horizontal gaze. SYN: n. nervi abducentis [TA].
- accessory cuneate n. [TA] a cell group lateral to the cuneate n. that receives posterior-root fibers 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 n.. SYN: n. cuneatus accessorius [TA], external cuneate n., lateral cuneate n., Monakow n..
- n. of accessory nerve a slender column of motor neurons extending longitudinally through central and lateral parts of the ventral horn of the upper six segments of the spinal cord, giving origin to the accessory nerve. SYN: n. nervi accessorii [TA].
- accessory nuclei of optic tract [TA] small groups of neuron cell bodies located along the trajectory of optic fibers in the mesencephalon. These consist of the posterior n. [TA] (n. posterior [TA]), medial n. [TA] (n. medialis [TA]), and lateral n. [TA] (n. lateralis [TA]), which are also called the posterior, medial and lateral terminal nuclei. The connections of these nuclei, along with the n. of the optic tract, comprise the accessory optic system that appears to be concerned with retinal slip in specific directions. SYN: nuclei accessorii tractus optici [TA].
- n. accumbens [TA] the region of fusion between the head of the caudate n. and the putamen, covered on the ventral side by the olfactory tubercle. The former name n. accumbens septi (“a n. leaning against the septum”) refers to a medial, hook-shaped expansion of this anteroventral region of the striatum, which curves under the floor of the frontal horn of the lateral ventricle and ascends for some distance into the ventral half of the septal region. Composed of a pars lateralis [TA] (lateral part [TA] or core region [TAalt]) and a pars medialis [TA] (medial part [TA] or shell region [TAalt]).
- ambiguus n. SYN: n. ambiguus.
- n. ambiguus [TA] a very slender, longitudinal column of motor neurons in the ventrolateral medulla oblongata; its efferent fibers leave with the vagus and glossopharyngeal nerve and innervate the striated muscle fibers of the pharynx (including the musculus levator veli palatini) and the vocal cord muscles of the larynx. SYN: ambiguus n..
- n. amygdalae SYN: amygdaloid body.
- n. amygdalae corticalis [TA] SYN: cortical amygdaloid n..
- n. amygdalae interstitialis [TA] SYN: interstitial amygdaloid n..
- amygdaloid n. SYN: amygdaloid body.
- n. anterior corporis trapezoidei [TA] SYN: anterior n. of trapezoid body. See nuclei of trapezoid body.
- anterior interpositus n. [TA] one of two cerebellar nuclei interposed between the dentate and the fastigial nuclei. SYN: n. interpositus anterior [TA].
- anterior olfactory n. [TA] a n. located in the olfactory tract and prominent in microsmatic animals; receives input from the olfactory bulb and projects to the bulb, to other targets of olfactory fibers, and to its contralateral counterpart. SYN: n. olfactorius anterior [TA].
- anterior periventricular n. [TA] See anterior hypothalamic area. SYN: n. periventricularis ventralis [TA].
- anterior nuclei of thalamus [TA] collective term for three groups of nerve cells that together form the anterior thalamic tubercle : the anteroventral n. [TA], a relatively large n.; the anteromedial n. [TA]; and the anterodorsal n. [TA], a small (but large-celled) n.. These nuclei receive the mamillothalamic tract from the mamillary body, and additional afferents by way of the fornix; they project collectively to the cortex of the cingulate and parahippocampal gyrus. SYN: nuclei anteriores thalami [TA].
- anterior n. of trapezoid body [TA] See nuclei of trapezoid body. SYN: n. anterior corporis trapezoidei [TA].
- n. anterolateralis [TA] See anterior horn.
- anteromedial n. [TA] See anterior horn.
- arcuate n. [TA] 1. SYN: n. arcuatus of intermediate hypothalamic area [TA], posterior periventricular n. [TA]. SYN: arcuate n. of thalamus. 2. a cell group in the hypothalamus, located in the lowest part of the infundibulum adjacent to the median eminence. SYN: n. arcuatus of medulla oblongata [TA]. 3. a variable assembly of small cell groups, probably outlying components of the ponting nuclei, on the ventral and medial aspects of the pyramid in the medulla oblongata. SYN: n. arcuatus [TA].
- arcuate n. of thalamus the small ventral region of the ventral posteromedial n. of thalamus in which the fibers of the gustatory lemniscus and secondary trigeminal tracts terminate; it projects to the lower part of the postcentral gyrus of the cerebral cortex. SYN: arcuate n. (1) [TA], n. arcuatus thalami, semilunar n. of Flechsig, thalamic gustatory n..
- n. arcuatus [TA] SYN: arcuate n.. See intermediate hypothalamic area.
- autonomic (visceral motor) nuclei nuclei located in the spinal cord (T1–L2, S2–S4) and in the brainstem (Edinger-Westphal n., superior and inferior salivatory nuclei, dorsal vagal n., and parts of the ambiguus n.) from which general visceral efferent preganglionic fibers arise; may be sympathetic (T1–L2) or parasympathetic (craniosacral); hypothalamic nuclei/areas function in concert with autonomic nuclei.
- basal nuclei [TA] n. of the cerebral hemisphere that originally included the caudate and lenticular nuclei, the claustrum, and the amygdaloid body (complex); functionally the term basal nuclei now specifies the caudate and lenticular nuclei and adjacent cell groups having important connections therewith (subthalamic n.; substantia nigra and partes compacta and reticulata); amygdaloid complex now known to be part of the limbic system; SEE ALSO: basal ganglia, under ganglion. SYN: nuclei basales [TA].
- nuclei basales [TA] SYN: basal nuclei.
- basal n. of Ganser a large group of large cells in the innominate substance, ventral to the lentiform n.. SYN: n. basalis of Ganser.
- basket n. nuclear structure that may be seen in Iodamoeba bütschlii cysts and occasionally in trophozoites; in stained preparations, fibrils may be seen running between the karyosome and the chromatin granules.
- branchiomotor nuclei collective term for those motoneuronal nuclei of the brainstem (n. ambiguus, facial motor n., motor n. of the trigeminus) that develop from the branchiomotor column of the embryo and innervate striated muscle fibers (muscles of mastication, facial musculature, pharynx, and vocal cord muscles) associated with the branchial arches. SYN: special visceral efferent nuclei, special visceral motor nuclei.
- n. caeruleus [TA] a shallow depression, blue in the fresh brain, lying laterally in the most rostral portion of the rhomboidal fossa near the cerebral aqueduct; it lies near the lateral wall of the fourth ventricle and consists of about 20,000 melanin-pigmented neuronal cell bodies whose norepinephrine-containing axons have a remarkably wide distribution in the cerebral cortex, dorsal thalamus, amygdaloid complex and hippocampus, mesencephalic tegmentum, cerebellar nuclei and cortex, various nuclei in the pons and medulla, and the gray matter of the spinal cord.
- nuclei camporum perizonalium [TA] SYN: nuclei of perizonal fields.
- caudal pontine reticular n. [TA] See reticular nuclei of pons. SYN: n. reticularis pontis caudalis [TA].
- caudate n. [TA] an elongated curved mass of gray matter, consisting of an anterior thick portion, the caput [TA] or head [TA], which protrudes into the anterior horn of the lateral ventricle, a portion extending along the floor of the body of the lateral ventricle, known as the corpus [TA] or body [TA], and an elongated curved thin portion, the cauda [TA] or tail [TA], which curves downward, backward, and forward in the temporal lobe in the dorsolateral wall of the lateral ventricle. SYN: n. caudatus [TA], caudate (2), caudatum.
- n. caudatus [TA] SYN: caudate n..
- central n. [TA] See anterior horn.
- central lateral n. of thalamus [TA] the most lateral of the intralaminar nuclei of the thalamus. SYN: n. centralis lateralis [TA].
- centromedian n. [TA] a large, lentil-shaped cell group, the largest and most caudal of the intralaminar nuclei, located within the lamina medullaris interna of the thalamus between the mediodorsal n. and ventrobasal n.; so called by Luys because of its prominent appearance on frontal sections midway between the anterior and posterior pole of the human thalamus. The n. receives numerous fibers from the internal segment of the globus pallidus by way of the thalamic fasciculus, ansa lenticularis, and lenticular fasciculus as well as projections from area 4 of the motor cortex; its major efferent connection is with the putamen although collaterals reach broad areas of the cerebral cortex. SYN: n. centromedianus [TA], centre médian de Luys, centrum medianum.
- n. centromedianus [TA] SYN: centromedian n..
- cerebellar nuclei [TA] collective term for the dentate, globosus, and emboliform nuclei, and the tectal and fastigial nuclei of the cerebellum. SYN: nuclei cerebelli [TA].
- nuclei cerebelli [TA] SYN: cerebellar nuclei.
- cochlear nuclei [TA] SYN: nuclei cochleares.
- nuclei cochleares [TA] the n. cochlearis posterior [TA] (posterior cochlear n. [TA] or dorsal cochlear n. [TAalt]) and n. cochlearis anterior [TA] (anterior cochlear n. [TA] or ventral cochlear n. [TAalt]) are located on the dorsal and lateral surface of the inferior cerebellar peduncle, in the floor of the lateral recess of the rhomboid fossa. The anterior cochlear nuclei may be divided into an anterior part [TA] (pars anterior [TA]) and a posterior part [TA] (pars posterior [TA]); they receive the incoming fibers of the cochlear part of the vestibulocochlear nerve and are the major source of origin of the lateral lemniscus or central auditory pathway. SYN: cochlear nuclei [TA], nuclei nervi cochlearis.
- n. cochlearis anterior [TA] See nuclei cochleares.
- n. cochlearis posterior [TA] See nuclei cochleares.
- nuclei colliculi inferioris [TA] SYN: nuclei of inferior colliculus.
- nuclei corporis mamillaris SYN: nuclei of mammillary body.
- nuclei of cranial nerves groups of nerve cells associated with the cranial nerves either as motor nuclei (nuclei originis) or sensory nuclei (nuclei terminationis). SYN: n. nervi cranialis [TA].
- cuneate n. [TA] the larger Burdach n.; one of the three nuclei of the posterior column of the spinal cord; located near the dorsal surface of the medulla oblongata at and below the level of the obex, the n. receives posterior root fibers corresponding to the sensory innervation of the arm and hand of the same side; it consists of a pars centralis [TA] (central part [TA], cell nest region [TAalt]) and a pars rostralis [TA] (rostral part [TA], shell region [TAalt]; together with its medial companion, the gracile n., it is the major source of origin of the medial lemniscus. SYN: n. cuneatus pars, rostralis [TA], n. cuneatus, pars centralis [TA], n. cuneatus [TA], Burdach n., n. funiculi cuneati, n. of cuneate fasciculus.
- n. cuneatus [TA] SYN: cuneate n..
- n. cuneiformis [TA] SYN: cuneiform n.. See reticular nuclei of mesencephalon.
- n. of Darkschewitsch an ovoid cell group in the ventral central gray substance rostral to the oculomotor n., receiving fibers from the vestibular nuclei by way of the medial longitudinal fasciculus; projections are not known, although some cross in the posterior commissure.
- Deiters n. See vestibular nuclei.
- dentate n. of cerebellum the most lateral and largest of the cerebellar nuclei; it receives the axons of Purkinje cells from the lateral area of the cerebellar cortex (so-called neocerebellum) and input via collaterals of cerebellar afferent fibers en route to the overlying cerebellar cortex; together with the more medially located globosus and emboliform nuclei, it is the major source of fibers composing the massive superior cerebellar peduncle or brachium conjunctivum. SYN: n. dentatus [TA], n. lateralis cerebelli, corpus dentatum, dentatum.
- n. dentatus [TA] SYN: dentate n. of cerebellum.
- diploid n. a n. containing the diploid or normal double complement of chromosomes for one somatic cell.
- dorsal accessory olivary n. a detached part of the olivary n. dorsal to the latter's main body. SYN: n. olivaris accessorius posterior [TA], posterior accessory olivary n. [TA].
- dorsal lateral geniculate n. [TA] main division of the lateral geniculate body; consists of two magnocellular layers [TA] (strata magnocellularia [TA]) and four parvocellular layers [TA] (strata parvocellularia [TA]) and serves as a processing station in the major pathway from the retina to the cerebral cortex, receiving fibers from the optic tract and giving rise to the geniculocalcarine radiation to the visual cortex in the occipital lobe. SYN: n. dorsalis corporis geniculati lateralis [TA].
- dorsal premammillary n. [TA] See posterior hypothalamic area. SYN: n. premammillaris dorsalis [TA].
- dorsal n. of thalamus one of the major subdivisions of the thalamus; the composite dorsal n. includes the n. lateralis anterior or dorsalis, n. lateralis intermedius, n. lateralis posterior, and pulvinar; together, these cell groups form most of the free dorsal surface of the posterior half of the thalamus and project to a very large region of parietal, occipitoparietal, and temporal cortex; its afferent connections are largely obscure, but the n. lateralis posterior and the pulvinar receive a projection from the superior colliculus. SYN: n. dorsales thalami [TA].
- dorsal n. of trapezoid body a term sometimes used to designate t6 superior olivary n. located ventrolaterally in the lower pontine tegmentum, immediately dorsal to the trapezoid body; the n. receives fibers from both the ipsilateral and contralateral cochlear nuclei and contributes fibers to the lateral (auditory) lemniscus of both sides. It is believed to be prominently involved in the function of spatial localization of sound. SYN: n. dorsalis corporis trapezoidei, oliva superior, superior olive.
- dorsolateral n. See anterior horn.
- dorsomedial hypothalamic n. SYN: dorsomedial n. of hypothalamus.
- dorsomedial n. of hypothalamus [TA] an oval cluster of cells located dorsal to the ventromedial hypothalamic n.. SYN: n. dorsomedialis hypothalami [TA], dorsomedial hypothalamic n..
- n. dorsomedialis [TA] SYN: dorsomedial n.. See intermediate hypothalamic area.
- n. dorsomedialis hypothalami [TA] SYN: dorsomedial n. of hypothalamus.
- droplet nuclei particles 1–10 μm in diameter, implicated in spread of airborne infection; the dried residue formed by evaporation of droplets coughed or sneezed into the atmosphere or by aerosolization of infective material.
- Edinger-Westphal n. a small group of preganglionic parasympathetic motor neurons in the midline near the rostral pole of the oculomotor n. 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 n. or its efferent fibers causes maximal paralytic dilation of the pupil; also demonstrated to project fibers to lower levels of the brainstem and all spinal levels. SYN: visceral nuclei of oculomotor nerve [TA].
- emboliform n. one of two cerebellar nuclei interposed between the dentate and the fastigial nuclei; a small wedge-shaped n. in the central white substance of the cerebellum just internal to the hilus of the dentate n.; 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. SYN: n. emboliformis, embolus (2).
- n. emboliformis emboliform n..
- endolemniscal n. [TA] small clusters of neuron cell bodies located on the lateral aspect of the medial lemniscus in the medulla oblongata, or insinuated within the fascicles of this fiber bundle. SYN: n. endolemniscalis [TA].
- n. endolemniscalis [TA] SYN: endolemniscal n..
- n. endopeduncularis [TA] SYN: endopeduncular n.. See dorsal hypothalamic area.
- facial n. a group of motor neurons located in the ventrolateral region of the lower pontine tegmentum and innervating the facial muscles, the stapedius muscle in the middle ear, the posterior limb of the musculus digastricus, and the stylohyoid muscle. SYN: motor n. of facial nerve [TA], n. nervi facialis [TA], facial motor n., n. facialis.
- fastigial n. [TA] the most medial of the cerebellar nuclei, lying medial to the interpositus n., 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. SYN: n. fastigii [TA], n. medialis cerebelli, fastigatum, n. tecti, roof n., tectal n..
- n. fastigii [TA] SYN: fastigial n..
- filiform n. SYN: paraventricular n. [TA] of hypothalamus.
- n. filiformis SYN: paraventricular n. [TA] of hypothalamus.
- n. funiculi cuneati SYN: cuneate n..
- n. funiculi gracilis SYN: gracile n..
- gametic n. SYN: micronucleus (2).
- germ n. SYN: micronucleus (2).
- gigantocellular n. of medulla oblongata [TA] one of the three major nuclei of the reticular formation of the brainstem; its small ventromedial portion is designated as pars alpha [TA]. SYN: n. gigantocellularis medullae oblongatae [TA].
- n. globosus globosus n..
- globosus n. one of two cerebellar nuclei interposed between the fastigial and the dentate nuclei; a group of two or three small masses of gray substance in the white central core of the cerebellum, medial to the emboliform n.; 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. SYN: n. globosus, spherical n..
- n. of Goll SYN: gracile n..
- gonad n. SYN: micronucleus (2).
- gracile n. [TA] the medial one of the three nuclei of the dorsal column, the remaining two being the cuneate n. and the accessory cuneate n., which corresponds to the clava; it can be divided into a pars centralis [TA] (central part [TA]), cell nest region [TAalt]), a pars rostralis [TA] (rostral part [TA], shell region [TAalt]), and subnucleus rostrodorsalis [TA] (rostrodorsal subnucleus [TA], cell group z [TAalt]; it receives dorsal-root fibers conveying sensory innervation of the leg, and lower trunk, and projects, by way of the medial lemniscus, to the ventral posterolateral posterior n. of the thalamus. SYN: n. gracilis [TA], n. fasciculi gracilis, n. funiculi gracilis, n. of Goll.
- n. gracilis [TA] SYN: gracile n..
- habenular nuclei the gray matter of the habenula, composed of a small-celled medial habenular n. [TA] (n. habenularis medialis [TA]) and a large-celled lateral habenular n. [TA] (n. habenularis lateralis [TA]); both nuclei receive fibers from basal forebrain regions (septum, basal n., lateral preoptic n.); the lateral habenular n. receives an additional projection from the medial segment of the globus pallidus. Both nuclei project by way of the retroflex fasciculus to the interpeduncular n. and a medial zone of the midbrain tegmentum. SYN: ganglion habenulae.
- hypoglossal n. the motor n. innervating the intrinsic and four of the five extrinsic muscles of the tongue; it is located in the medulla oblongata near the midline, immediately beneath the floor of the inferior recess of the rhomboid fossa. SYN: n. nervi hypoglossi [TA], n. of hypoglossal nerve [TA].
- nuclei of inferior colliculus [TA] the nerve cell groups composing the colliculus inferior consisting of a central n. [TA] (n. centralis [TA]), an external n. [TA] (n. externus [TA] or n. lateralis [TAalt]), and a pericentral n. [TA] (n. pericentralis [TA]). SYN: nuclei colliculi inferioris [TA].
- inferior olivary n. a large aggregate of small densely packed nerve cells consisting of medial and dorsal accessory olivary nuclei and a principal olivary n. that is 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 fibers. Its afferent connections include fibers from the spinal cord, dentate n., and motor cortex, but its major input appears to be the central tegmental tract originating from multiple nuclei at midbrain levels. SYN: n. olivaris inferior.
- inferior salivatory n. [TA] a group of preganglionic parasympathetic motor neurons located in the reticular formation of the medulla oblongata dorsal to the n. ambiguus; its axons leave the brain with the glossopharyngeal nerve and govern secretion from the parotid gland by the intermediary of the ganglion oticum; cells of the inferior and superior n. are scattered and overlapping in lateral regions of the reticular formation. SYN: n. salivatorius inferior [TA], inferior salivary n..
- inferior vestibular n. [TA] n. vestibularis inferior. SEE ALSO: vestibular nuclei. SYN: n. vestibularis inferior [TA].
- intercalated n. [TA] a small collection of nerve cells in the medulla oblongata lying lateral to the hypoglossal n.. SYN: n. intercalatus [TA], Staderini n..
- n. intercalatus [TA] SYN: intercalated n..
- intermediolateral n. [TA] 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 fibers of the sympathetic system. SYN: n. intermediolateralis [TA], intermediolateral cell column of spinal cord.
- n. intermediolateralis [TA] SYN: intermediolateral n..
- intermediomedial n. [TA] a small group of scattered visceral motor neurons immediately ventral to the thoracic n. in the thoracic and upper two lumbar segments of the spinal cord; considered to receive visceral afferent fibers at all spinal levels. SYN: n. intermediomedialis [TA].
- n. intermediomedialis [TA] SYN: intermediomedial n..
- interpeduncular n. [TA] 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. SYN: n. interpeduncularis [TA], ganglion isthmi, Gudden ganglion, intercrural ganglion, interpeduncular ganglion.
- n. interpeduncularis [TA] SYN: interpeduncular n..
- n. interpositus SYN: interpositus n..
- interpositus n. collective term denoting the globosus n. and emboliform n. of the cerebellum. SYN: n. interpositus.
- interstitial n. [TA] a group of widely spaced, medium-sized neurons in the dorsomedial region of the upper mesencephalic tegmentum, immediately lateral to the n. of Darkschewitsch; together with the latter, the interstitial n. is closely associated with the medial longitudinal fasciculus, via which it receives fibers from the vestibular nuclei and projects crossed fibers via the posterior commissure to the oculomotor n.; also projects fibers 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. SYN: n. interstitialis [TA], interstitial n. of Cajal.
- interstitial nuclei of anterior hypothalamus [TA] See anterior hypothalamic area. SYN: nuclei interstitiales hypothalami anterioris [TA].
- interstitial n. of Cajal SYN: interstitial n..
- n. interstitiales fasciculi longitudinalis medialis [TA] SYN: interstitial n. of medial longitudinal fasciculus.
- nuclei interstitiales hypothalami anterioris [TA] SYN: interstitial nuclei of anterior hypothalamus. See anterior hypothalamic area.
- n. interstitialis [TA] SYN: interstitial n..
- interstitial n. of medial longitudinal fasciculus [TA] small groups of cells located laterally adjacent to the medial longitudinal fasciculus in the area of the oculomotor n.; involved in eye movement through connections with the oculomotor and trochlear nuclei. These connections are primarily ipsilateral but have a bilateral component. SYN: n. interstitiales fasciculi longitudinalis medialis [TA].
- nuclei intralaminares thalami [TA] SYN: intralaminar nuclei of thalamus.
- intralaminar nuclei of thalamus [TA] collective term denoting several cell groups embedded in the internal medullary lamina of the thalamus : the central lateral n. [TA], paracentral n. [TA] (n. paracentralis [TA]), the central medial n. [TA] (n. centralis medialis [TA]), the centromedian n., and the parafascicular n. [TA] (n. parafascicularis [TA]). The central lateral and paracentral receive afferents from the cerebral cortex, brainstem, reticular formation, cerebellum, and spinal cord, and project more or less diffusely to large regions of the frontal and parietal cortex. The centromedian n. receives input from the internal segment of the globus pallidus and motor cortex and projects to the striatum and motor cortex. SEE ALSO: centromedian n.. SYN: nuclei intralaminares thalami [TA].
- Klein-Gumprecht shadow nuclei shadow nuclei in degenerating lymphoidocytes and macrolymphocytes in leukemia.
- lateral cervical n. [TA] diffusely arranged n. located in the dorsal portions of the lateral funiculus in about cervical levels C1–C3; synaptic station for the spinocervicothalamic tract.
- n. lateralis corporis trapezoidei [TA] SYN: lateral n. of trapezoid body. See nuclei of trapezoid body.
- nuclei of lateral lemniscus [TA] a substantial cell mass embedded in the lateral lemniscus, immediately below the latter's entry into the inferior colliculus; may be divided into a posterior n. of lateral lemniscus [TA] (dorsal n. of lateral lemniscus [TAalt], n. posterior lemnisci lateralis [TA]), an intermediate n. of lateral lemniscus [TA] (n. intermedius lemnisci lateralis [TA]), and an anterior n. of lateral lemniscus [TA] (n. anterior lemnisci lateralis [TA], ventral n. of lateral lemniscus [TAalt]); the n. represents a synaptic way-station for part of the fibers of the lateral lemniscus. SYN: nuclei lemnisci lateralis [TA].
- n. of the lateral olfactory tract [TA] See amygdaloid body. SYN: n. tractus olfactorii lateralis [TA].
- lateral parabrachial n. a cell group located lateral to the brachium conjunctivum in rostral regions of the pons; may be divided into a pars lateralis [TA] (lateral part [TA]), a pars medialis [TA] (medial part [TA]), pars posterior [TA] (posterior part [TA]), and a pars anterior [TA] (anterior part [TA]). SEE ALSO: parabrachial nuclei. SYN: n. parabrachialis lateralis [TA].
- lateral pericuneate n. [TA] a small flattened group of neuron cell bodies located ventrolateral to the cuneate n. and insinuated between the cuneate fasciculus and accessory cuneate n. and the spinal tract of the trigeminal nerve. SYN: n. pericuneatus lateralis [TA].
- lateral preoptic n. [TA] a vaguely defined group of nerve cells in the lateral zone of the preoptic region. SEE ALSO: anterior hypothalamic area. SYN: n. preopticus lateralis [TA].
- lateral reticular n. group of cells in the medulla oblongata located between the inferior olive and the descending trigeminal n. and tract; composed of a magnocellular part [TA] (pars magnocellularis [TA]), a parvocellular part [TA] (pars parvocellularis [TA]), and a subtrigeminal part [TA] (pars subtrigeminalis [TA]); receives fibers from the spinal and motor cortex and projects to the cerebellum. SYN: lateral n. of medulla oblongata.
- lateral superior olivary n. [TA] See superior olivary n.. SYN: n. olivaris superior lateralis [TA].
- lateral n. of trapezoid body [TA] See nuclei of trapezoid body. SYN: n. lateralis corporis trapezoidei [TA].
- lateral tuberal nuclei [TA] See intermediate hypothalamic area.
- lateral vestibular n. [TA] n. vestibularis lateralis. See vestibular nuclei. SYN: n. vestibularis lateralis [TA].
- lenticular n.
- n. lentiformis [TA] SYN: lentiform n..
- n. of Luys SYN: subthalamic n..
- nuclei of mammillary body located in the posterior hypothalamic area, this group of nuclei consists of a large-celled lateral n. of the mammillary body and larger medial nuclei of the mammillary body, dorsal and ventral premammillary nuclei, and supramammillary n.; the first two form the elevation seen on the ventral aspect of the diencephalon, the mammillary body. SYN: n. corporis mammillaris lateralis [TA], n. corporis mammillaris medialis [TA], nuclei corporis mamillaris.
- medial accessory olivary n. [TA] a detached part of the olivary n. medial to the latter's main body, against the lateral side of the medial lemniscus and pyramidal tract. SYN: n. olivaris accessorius medialis [TA].
- medial central n. of thalamus a small cell group in the interthalamic adhesion of the thalamus, occupying the midline region of the internal medullary lamina, between the left and the right paracentral n.. SYN: n. medialis centralis thalami.
- medial dorsal n. [TA] of thalamus a large, composite cell group in the dorsomedial region of the thalamus having reciprocal connections with the entire extent of the frontal cortex anterior to the motor cortex (area 4) and premotor cortex (area 6). The afferent connections of the medial dorsal n. also include projections from the olfactory cortex and amygdala. Composed of a pars parvocellularis lateralis [TA] (lateral n. [TA] or parvocellular n. [TAalt]), a pars magnocellularis medialis [TA] (medial n. [TA] or magnocellular n. [TAalt]), and a pars paralaminaris [TA] (paralaminar part [TA] or pars laminaris [TAalt]). SYN: mediodorsal n., n. medialis thalami, n. mediodorsalis.
- medial geniculate nuclei groups of cell bodies that function as the last of a series of processing stations along the auditory conduction pathway to the cerebral cortex, receiving the brachium of the inferior colliculus and giving rise to the auditory radiation to the auditory cortex in the superior temporal gyrus. SYN: nuclei corporis geniculati medialis [TA], n. of medial geniculate body.
- medial geniculate nuclei [TA] nerve cells that collectively form a surface elevation, the medial geniculate body; they comprise a ventral principal n. [TA], a dorsal n. [TA], and a small medial magnocellular n.; relay of auditory input to auditory cortex
- n. medialis cerebelli fastigial n..
- n. medialis corporis trapezoidei [TA] SYN: medial n. of trapezoid body. See nuclei of trapezoid body.
- medial parabrachial n. [TA] a cell group located medial to the brachium conjunctivum in rostral areas of the pons; may be divided into a pars medialis [TA] (medial part [TA]) and a pars lateralis [TA] (lateral part [TA]). SEE ALSO: parabrachial nuclei. SYN: n. parabrachialis medialis [TA].
- medial pericuneate n. [TA] a small group of neuron cell bodies located immediately ventromedial to the cuneate n., insinuated in a diffuse layer of cells, the pericuneate matrix. SYN: n. pericuneatus medialis [TA].
- medial preoptic n. [TA] a group of nerve cells forming the medial zone of the preoptic region. SYN: n. preopticus medialis [TA].
- medial nuclei of thalamus [TA] collective group of cells comprising the large medial dorsal n. (or dorsomedial n.) and its subdivisions (lateral n. or parvocellular n., medial n. or magnocellular n., paralaminar part or pars paralaminaris) and the medial ventral n. [TA] (n. medioventralis [TA]). SYN: nuclei mediales thalami [TA].
- medial n. of trapezoid body [TA] See nuclei of trapezoid body. SYN: n. medialis corporis trapezoidei [TA].
- mesencephalic n. of trigeminal nerve [TA] a long, narrow plate of unipolar neurons extending throughout the length of the midbrain, in and along the lateral angle of the central gray substance. The n. is the single known instance of primary sensory neurons enclosed in the central nervous system instead of in a peripheral sensory ganglion. Its peripheral axonal processes pass with the trigeminal nerve, give collaterals to the trigeminal motor n., and terminate in the muscles of mastication. SYN: n. mesencephalicus nervi trigemini [TA].
- motor n. of trigeminal nerve [TA] a group of motor neurons innervating the muscles of mastication (masseter, temporalis, and internal and external pterygoid muscles) and the musculi tensor tympani and tensor veli palatini. The n. lies in the upper pontine tegmentum medial to the principal sensory n. of the trigeminal nerve. SYN: n. motorius nervi trigemini [TA], masticatory n., motor n. of trigeminus, n. masticatorius.
- n. nervi hypoglossi [TA] SYN: hypoglossal n..
- n. nervi oculomotorii [TA] SYN: oculomotor n..
- n. niger SYN: substantia nigra.
- oculomotor n. 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 n. is the Edinger-Westphal n., which innervates the musculi sphincter pupillae and ciliaris via the ciliary ganglion. The oculomotor n. lies in the rostral half of the midbrain, near the midline in the most ventral part of the central gray substance; fibers of the medial longitudinal fasciculus form its lateral borders. SYN: n. nervi oculomotorii [TA], n. of oculomotor nerve [TA].
- n. olivaris principalis [TA] SYN: principal olivary n..
- Onuf n. a group of small somatic motor neurons in the ventral horn of the spinal cord at sacral 2 level that innervate the vesicorectal sphincters, that is, the external anal and the urethral sphincter; Onuf n. has been identified in the cat, dog, and human. SYN: n. of pudendal nerve [TA]. [Onufrowicz, Wladislaus, Swiss anatomist.]
- oral pontine reticular n. [TA] See reticular nuclei of pons. SYN: n. reticularis pontis oralis [TA].
- nuclei of origin collections of motor neurons (forming a continuous column in the spinal cord, discontinuous in the medulla and pons) giving origin to the spinal and cranial motor nerves. SYN: n. originis [TA], motor nuclei.
- n. originis [TA] SYN: nuclei of origin.
- parabigeminal n. [TA] a group of neuron cell bodies located in the lateral position of the midbrain in the area of spinothalamic fibers; ventrolaterally adjacent to the inferior colliculus with which it has interconnections. SYN: n. parabigeminalis [TA].
- n. parabigeminalis [TA] SYN: parabigeminal n..
- parabrachial nuclei [TA] the cell groups flanking the brachium conjunctivum at levels immediately caudal to the inferior colliculus; they serve as way-stations in the pathways ascending from the n. of solitary tract to the thalamus and hypothalamus and receive afferent fibers from the hypothalamus and amygdaloid body. SYN: nuclei parabrachiales [TA].
- nuclei parabrachiales [TA] SYN: parabrachial nuclei.
- n. paracentralis thalami [TA] SYN: paracentral n. of thalamus.
- paracentral n. of thalamus [TA] one of the intralaminar nuclei of the thalamus, medial to the central lateral n.. SYN: n. paracentralis thalami [TA].
- n. paralemniscalis [TA] SYN: paralemniscal n.. See reticular nuclei of pons.
- paramedial reticular n. [TA] See reticular nuclei of pons.
- paranigral n. [TA] a small cell cluster located in the ventromedial regions of the midbrain and insinuated between the medial aspect of the substantia nigra and the interpeduncular n.. SYN: n. paranigralis [TA].
- n. paranigralis [TA] SYN: paranigral n..
- parapeduncular n. [TA] See reticular nuclei of mesencephalon. SYN: n. parapeduncularis [TA].
- n. parapeduncularis [TA] SYN: parapeduncular n.. See reticular nuclei of mesencephalon.
- paraventricular n. [TA] See anterior hypothalamic area.
- n. paraventricularis hypothalami SYN: paraventricular n. [TA] of hypothalamus.
- paraventricular n. [TA] of hypothalamus a triangular group of large magnocellular neurons in the periventricular zone of the anterior half of the hypothalamus. The cells of the n. are similar to those of the supraoptic n.; 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 fibers to the brainstem nuclei (dorsal motor n. and solitary n.) and to the intermediolateral cell column of the spinal cord at thoracic, lumbar, and spinal levels; similar descending autonomic fibers arise from the lateral and posterior hypothalamic nuclei. SYN: filiform n., n. filiformis, n. paraventricularis hypothalami.
- pedunculopontine tegmental n. [TA] See reticular nuclei of mesencephalon. SYN: n. tegmentalis pedunculopontinus [TA].
- n. perifornicalis [TA] SYN: perifornical n..
- perihypoglossal nuclei [TA] nuclei found in the floor of the 4th ventricle in relation to the hypoglossal n.; term includes the prepositus and intercalated nuclei and the n. of Roller.
- peripeduncular n. [TA] a group of neuron cell bodies that form a thin, caplike configuration over the dorsolateral aspect of the crus cerebri; many of its cells are acetylcholinesterase-positive. SYN: n. peripeduncularis [TA].
- n. peripeduncularis [TA] SYN: peripeduncular n..
- peritrigeminal n. [TA] small diffuse clusters of cells located mainly on the lateral aspect of the spinal tract of the trigeminal nerve, or insinuated within this fiber bundle at the level of and caudal to the obex. SYN: n. peritrigeminalis [TA].
- n. peritrigeminalis [TA] SYN: peritrigeminal n..
- n. periventricularis posterior [TA] SYN: posterior periventricular n.. See intermediate hypothalamic area.
- n. periventricularis ventralis [TA] SYN: anterior periventricular n.. See anterior hypothalamic area.
- periventricular preoptic n. [TA] See anterior hypothalamic area. SYN: n. preopticus periventricularis [TA].
- nuclei of perizonal fields [TA] small groups of cells distributed along the course of, and insinuated within, pallidofugal fibers that form the lenticular fasciculus (n. of ventral field [TA], n. campi ventralis [TA], n. of field H2), that arch through the prerubral field (n. of medial field [TA], n. campi medialis [TA], n. of field H) and the thalamic fasciculus (n. of dorsal field [TA], n. campi dorsalis [TA], n. of field H1). SEE ALSO: fields of Forel, under field. SYN: nuclei camporum perizonalium [TA].
- Perlia n. a small cell group located between the somatic cell columns of the oculomotor nuclei. Because it is placed between the groups of motor neurons innervating, respectively, the left and right medial rectus muscles, the n. is considered to represent possibly an integrating mechanism for ocular convergence. SYN: convergence n. of Perlia, Spitzka n..
- phenanthrene n. misnomer for tetracyclic steroid n..
- n. of phrenic nerve [TA] neuron cell bodies located in the more medial portions of the anterior horn at cervical levels C3 to C7 that innervate the diaphragm via the phrenic nerve. SEE ALSO: phrenic n.. SYN: n. nervi phrenici [TA], phrenic n..
- pontine nuclei [TA] the massive gray matter, composed of individual nuclei, that fills the basilar pons. These nuclei are of fairly homogenous architecture and project primarily to the contralateral side of the cerebellum by way of the middle cerebellar peduncle; there is a modest ipsilateral pontocerebellar projection. Their main afferents come from the entire extent of the cerebral neocortex by way of the corticopontine fibers (longitudinal pontine bundles); thus, the pontine nuclei form a major way-station in the impulse conduction from the cerebral cortex off one hemisphere to the posterior lobe off the opposite cerebellum. The pontine nuclei consist of: n. anterior [TA] (anterior n. [TA], ventral n. [TAalt]), n. lateralis [TA] (lateral n. [TA]), n. medianus [TA] (median n. [TA]), n. paramedianus [TA] (paramedian n. [TA]), n. peduncularis [TA] (peduncular n. [TA], peripeduncular n. [TAalt]), n. posterior lateralis [TA] (posterolateral n. [TA], dorsolateral n. [TAalt]), and n. posterior medialis [TA] (posteromedial n. [TA], dorsomedial n. [TAalt]). The n. reticularis tegmenti pontis [TA] (reticulotegmental n. [TA]) is located at the interface of tegmental and basilar portions of the pons and is sometimes grouped with the pontine nuclei. SYN: nuclei pontis [TA], pontine gray matter.
- nuclei pontis [TA] SYN: pontine nuclei.
- pontobulbar n. [TA] an irregularly shaped layer of cells located dorsal and lateral to the restiform body at mid to rostral levels of the medulla oblongata; becomes larger immediately ventrolateral to the restiform body at the medulla-pons junction; these cells are similar to those of the basilar pontine nuclei. SYN: n. pontobulbaris [TA].
- n. pontobulbaris [TA] SYN: pontobulbar n..
- n. of posterior commissure [TA] a group of cells located immediately adjacent to the posterior commissure at the mesencephalon-diencephalon junction; may be divided into pars ventralis [TA] (ventral subdivision [TA]), pars dorsalis [TA] (dorsal subdivision [TA]), and pars interstitialis [TA] (interstitial subdivision [TA]). SYN: n. commissurae posterioris [TA].
- posterior hypothalamic n. [TA] a large, periventricular hypothalamic n. located dorsal to the mamillary body, continuous with the central gray substance of the mesencephalon. SYN: n. posterior hypothalami [TA].
- posterior n. of hypothalamus [TA] See posterior hypothalamic area. SYN: n. posterior hypothalamic [TA].
- posterior interpositus n. [TA] one of two cerebellar nuclei interposed between the fastigial and the dentate nuclei. SEE ALSO: globosus n.. SYN: n. interpositus posterior [TA].
- posterior thoracic n. [TA] 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. SYN: n. thoracicus posterior [TA], dorsal thoracic n., Clarke column, Clarke n., Stilling column, Stilling n..
- posterior n. of vagus nerve the visceral motor n. located in the vagal trigone (ala cinerea) of the floor of the fourth ventricle. It gives rise to the parasympathetic fibers of the vagus nerve innervating the heart muscle and the smooth musculature and glands of the respiratory and intestinal tracts. SYN: n. posterior nervi vagi [TA], n. dorsalis nervi vagi, dorsal motor n. of vagus, dorsal n. of vagus, dorsal vagal n., n. alae cinereae.
- posterolateral n. [TA] See anterior horn.
- n. posterolateralis [TA] See anterior horn.
- posteromedial n. [TA] See anterior horn.
- n. posteromedialis [TA] See anterior horn.
- precommissural septal n. [TA] the vertically oriented layer of neuron cell bodies located rostral to the anterior commissure in the base of the septum pellucidum. SYN: n. septalis precommissuralis [TA].
- n. preopticus periventricularis [TA] SYN: periventricular preoptic n.. See anterior hypothalamic area.
- pretectal nuclei [TA] group of cells, constituting several subnuclei, located rostral to the superior colliculus in the “pretectal” area; receive input from retinal ganglion cells (via the optic tract) and project bilaterally to the Edinger-Westphal n.; relay center for pupillary light reflex pathway; they consist of the n. pretectalis anterior [TA] (anterior pretectal n. [TA]), n. pretectalis olivaris [TA] (olivary pretectal n. [TA]), and n. pretectalis posterior [TA] (posterior pretectal n. [TA]). The n. tractus optici [TA] (n. of optic tract) is also usually grouped as one of the pretectal nuclei. SYN: nuclei pretectales [TA].
- nuclei pretectales [TA] SYN: pretectal nuclei.
- principal olivary n. [TA] the largest part of the inferior olivary complex, consisting of an undulating layer of cells formed by a dorsal lamella [TA] (lamella posterior [TA]) and a ventral lamella [TA] (lamella anterior [TA]) connected with each other laterally by a lateral lamella [TA] (lamella lateralis [TA]). The medially directed opening of this continuous cell layer is the hilum. SYN: n. olivaris principalis [TA].
- principal sensory n. of trigeminal nerve [TA] the term commonly used to designate the n. pontis nervi trigeminalis; located in pons lateral to the motor trigeminal n.; receives primary sensory (touch and pressure) input via the trigeminal nerve and projects to ventral posteromedial n. of thalamus. SYN: n. principalis nervi trigemini [TA], n. sensorius superior nervi trigemini, principal sensory n. of the trigeminus.
- n. pulposus [TA] the soft fibrocartilage central portion of the intervertebral disk; regarded as a derivative of the notochord. SYN: gelatinous n., n. gelatinosus, vertebral pulp.
- pulvinar nuclei [TA] the large caudal portion of the lateral thalamic nuclear group; may be divided into four nuclei on the basis of cytoarchitecture and connections: n. pulvinaris anterior [TA] (anterior pulvinar n. [TA]), n. pulvinaris inferior [TA] (inferior pulvinar n. [TA]), n. pulvinaris lateralis [TA] (lateral pulvinar n. [TA]), and n. pulvinaris medialis [TA] (medial pulvinar n. [TA]); functionally related to the visual system. SYN: nuclei pulvinares [TA].
- nuclei pulvinares [TA] SYN: pulvinar nuclei.
- pyrrole n. of porphyrins, a cyclic tetrapyrrole; four pyrrole groups joined into a ring structure by way of –CH= (methylidyne) bridges between the α (2) position of one pyrrole and the α′ (5) position of another pyrrole, the fourth pyrrole being joined to the first. SEE ALSO: porphin, porphyrin.
- raphe nuclei [TA] collective term denoting a variety of nerve cell groups in and along the median plane of the medulla oblongata [n. raphes obscurus [TA] (obscure raphe n. [TA]), n. raphes pallidus [TA] (pallidal raphe n. [TA]), and caudal portions of the n. raphes magnus [TA] (magnus raphe n. [TA])]; of the pons [rostral portions of the n. raphes magnus [TA] (magnus raphe n. [TA]), n. raphes pontis [TA] (pontine raphe n. [TA]), n. raphes medianus [TA] (median raphe n. [TA] or superior central n. [TAalt]), and caudal portions of the n. raphes posterior [TA] (posterior raphe n. [TA]) or dorsal raphe n. [TAalt])]; and of the mesencephalon [rostral portions of the n. raphe posterior [TA] (posterior raphe n. [TA]), n. linearis inferioris [TA] (inferior linear n. [TA]), n. linearis intermedius [TA] (intermediate linear n. [TA]), and n. linearis superior [TA] (superior linear n. [TA])]. These nuclei include neurons characterized by their containing the indolamine transmitter agent serotonin; their serotonin-carrying axons extend rostrally to the hypothalamus, septum, hippocampus, and cingulate gyrus and include projections to brainstem, cerebellum, and spinal cord. SYN: nuclei raphes [TA].
- nuclei raphes [TA] SYN: raphe nuclei.
- red n. a large, well-defined, somewhat elongated cell mass, reddish-gray in the fresh brain, located in the rostral mesencephalic tegmentum. This n. is composed of a caudal pars magnocellularis [TA] (magnocellular part [TA]), a rostral pars parvocellularis [TA] (parvocellular part [TA]) and a small pars posteromedialis [TA] (posteromedial part [TA], dorsomedial part [TAalt]). The n. receives a massive projection from the contralateral half of the cerebellum by way of the superior cerebellar peduncle and an additional projection from the ipsilateral motor cortex. Projections from the anterior interposed n. and motor cortex to the red n. are somatopically organized. Its efferent connections are with the contralateral rhombencephalic reticular formation and spinal cord by way of the rubrobulbar and rubrospinal tracts. Rubrospinal fibers have somatotopic origin. SYN: n. ruber [TA].
- reproductive n. SYN: micronucleus (2).
- reticular nuclei of the brainstem the vaguely delineated cell groups composing the gray matter of the reticular formation of the medulla oblongata, pons, and mesencephalon. In general, large-celled territories occupy the medial two-thirds of the reticular formation : some examples are gigantocellular n. of medulla oblongata, nuclei tegmenti pontis caudalis and oralis. Smaller groups of reticular nuclei are found laterally and in paramedian locations; lateral nuclei receive sensory collaterals and project medially; paramedian reticular nuclei largely project to the cerebellum. SEE ALSO: reticular formation.
- nuclei reticulares mesencephali [TA] SYN: reticular nuclei of mesencephalon.
- nuclei reticulares pontis [TA] SYN: reticular nuclei of pons.
- n. reticularis pontis caudalis [TA] SYN: caudal pontine reticular n.. See reticular nuclei of pons.
- n. reticularis tegmenti pontis [TA] See reticular nuclei of pons.
- n. reticularis thalami [TA] SYN: reticular n. of thalamus.
- reticular nuclei of medulla oblongata [TA] groups of neuron cell bodies located generally in the more central portions of each half of the medulla oblongata that are not all distinctly separated from each other yet may have specific connections. These nuclei are: gigantocellular reticular n. [TA] and its ventromedially located pars alpha [TA] (n. gigantocellularis [TA]), anterior gigantocellular reticular n. [TA] or ventral gigantocellular reticular n. [TAalt] (n. gigantocellularis anterior [TA]), lateral paragigantocellular reticular n. [TA] (n. paragigantocellularis lateralis [TA]), interfascicular n. of hypoglossal nerve [TA] (n. interfascicularis nervi hypoglossi [TA]), intermediate reticular n. [TA] (n. reticularis intermedius [TA]), parvocellular reticular n. [TA] (n. reticularis parvocellularis [TA]), posterior paragigantocellular reticular n. [TA] or dorsal paragigantocellular reticular n. [TAalt] (n. paragigantocellularis posterior [TA]) and medial reticular n. [TA] (n. reticularis medialis [TA]). The central reticular n. [TA] (n. reticularis centralis [TA]) can be divided into a dorsal part [TA] and a ventral part [TA] (pars dorsalis [TA], pars ventralis [TA]). The lateral reticular n. [TA] is located in the ventrolateral area of the medulla and can be divided into a magnocellular part [TA] (pars magnocellularis [TA]), a parvocellular part [TA] (pars parvocellularis [TA], and a subtrigeminal part [TA] (pars subtrigeminalis [TA]). SEE ALSO: reticular nuclei of the brainstem. SYN: n. reticulares medullae oblongatae [TA].
- reticular nuclei of mesencephalon [TA] diffusely arranged cell groups located in the dorsal and more medial area of the tegmentum of the mesencephalon. These nuclei are: cuneiform n. [TA] (n. cuneiformis [TA]), subcuneiform n. [TA] (n. subcuneiformis [TA]), parapeduncular n. [TA] (n. parapeduncularis [TA]), and the pedunculopontine tegmental n. [TA] (n. tegmentalis pedunculopontinus [TA]). This latter n. can be divided into a compact part [TA] or compact subnucleus [TAalt] (pars compacta [TA]) and a dissipated part [TA] or dissipated subnucleus [TAalt] (pars dissipata [TA]). SYN: nuclei reticulares mesencephali [TA].
- reticular nuclei of pons [TA] groups of cells located in the pontine tegmentum that are not clearly separate one from the other, but that have in some instances distinct connections. These nuclei are: caudal pontine reticular n. [TA] (n. reticularis pontis caudalis [TA]), oral pontine reticular n. [TA] (n. reticularis pontis oralis [TA]), paralemniscal n. [TA] (n. paralemniscalis [TA]), and the paramedian reticular n. [TA] (n. reticularis paramedianus [TA]). The reticulotegmental n. [TA] (n. reticularis tegmenti pontis [TA]) is located in the ventromedial portion of the pontine tegmentum and is correctly a part of the reticular complex of the pons; it is sometimes also associated with the dorsal extent of the basilar pontine nuclei. SYN: nuclei reticulares pontis [TA].
- reticular n. of thalamus [TA] 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 that traverse the n. The n. receives numerous fibers from the cerebral cortex, but it has no cortical projection. SYN: n. reticularis thalami [TA].
- n. reuniens [TA] a small cell group belonging to the midline group of thalamic nuclei and extending into the interthalamic adhesion (massa intermedia) when the latter is present.
- rhombencephalic gustatory n. the rostral one-third of the n. of solitary tract, receiving afferents from the facial, glossopharyngeal, and vagus nerves conveying impulses originating from the receptor cells of the taste buds.
- Roller n. 1. lateral n. of the accessory nerve; 2. a small bulbar n. lying immediately anterior to the hypoglossal n., considered one of the perihypoglossal nuclei. SEE subhypoglossal n..
- roof n. SYN: fastigial n..
- n. ruber [TA] SYN: red n..
- n. saguli [TA] SYN: sagulum n..
- sagulum n. [TA] a group of neuron cell bodies located between the lateral lemniscus and lateral surface of the brainstem immediately caudal to the inferior colliculus; functionally associated with the auditory system. SYN: n. saguli [TA].
- Schwalbe n. See vestibular nuclei.
- segmentation n. 1. the compound n. in the impregnated ovum, formed by conjugation of the nuclei of the ovum and spermatozoon (female and male pronuclei); 2. the zygote n. after it commences the first cleavage division.
- n. septalis precommissuralis [TA] SYN: precommissural septal n..
- septofimbrial n. [TA] See septal area.
- nuclei 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. This cell column is composed of smaller individual nuclei, and collectively they are the visceral sensory (visceral afferent) nuclei of the brainstem, receiving the afferent fibers of the vagus, glossopharyngeal, and facial nerves by way of the solitary tract. The caudal two-thirds of the n. processes impulses originating in the pharynx, larynx, intestinal and respiratory tracts, and heart and large blood vessel s; its rostral one-third receives impulses from the taste buds and is known as the rhombencephalic gustatory n.. The individual nuclei that collectively make up what is commonly called the solitary n. are: parasolitary n. [TA] (n. parasolitarius [TA]), commissural n. [TA] (n. commissuralis [TA]), gelatinous solitary n. [TA] (n. gelatinosus solitarius [TA]), intermediate solitary n. [TA] (n. intermedius solitarius [TA]), interstitial solitary n. [TA] (n. interstitialis solitarius [TA]), medial solitary n. [TA] (n. medialis solitarius [TA]), paracommissural solitary n. [TA] (n. paracommissuralis solitarius [TA]), posterior solitary n. [TA] or dorsal solitary n. [TAalt] (n. solitarius posterior [TA]), posterolateral solitary n. [TA] or dorsolateral solitary n. [TAalt] (n. solitarius posterolateralis [TA]), anterior solitary n. [TA] or ventral solitary n. [TAalt] (n. solitarius anterior [TA]), and naterolateral solitary n. [TA] or ventrolateral solitary n. [TA] (n. solitarius anterolateralis [TA]). SYN: nuclei tractus solitarii [TA].
- somatic n. SYN: macronucleus (2).
- somatic motor nuclei collective term indicating the motor nuclei innervating the tongue musculature (hypoglossal n.) and the extraocular eye muscles (abducens nucleu, trochlear n., and oculomotor n.), the sternocleidomastoid and trapezius muscles (accessory nerve) and the skeletal muscles of the body (ventral roots of spinal nerves).
- sperm n. the n. in the head of the spermatozoon, which becomes the male pronucleus after entering the ovum. SEE ALSO: pronucleus.
- spherical n. SYN: globosus n..
- spinal n. of trigeminal nerve [TA] the long sensory n. extending from the caudal border of the pontine sensory n. of the trigeminus down through the lateral region of the rhombencephalon into the upper three segments of the spinal cord's dorsal horn; it receives the fibers of the sensory root of the trigeminal nerve that descend along its lateral border as the spinal tract of trigeminal nerve [TA]. This n. is divided into a pars caudalis [TA] (caudal part [TA]), a pars interpolaris [TA] (interpolar part [TA]), and a subnucleus oralis [TA] (oral subnucleus [TA]). The pars caudalis is further organized into a subnucleus zonalis [TA] (zonal subnucleus [TA]), a subnucleus gelatinosus [TA] (gelatinosus subnucleus [TA]), and a subnucleus magnocellularis [TA] (magnocellular subnucleus [TA]). SYN: n. spinalis nervi trigemini [TA], descending n. of the trigeminus, spinal n. of the trigeminus.
- Staderini n. SYN: intercalated n..
- subcaeruleus n. [TA] diffusely organized n. of noradrenergic cells located ventral to the n. caeruleus.
- subcuneiform n. [TA] See reticular nuclei of mesencephalon. SYN: n. subcuneiformis [TA].
- n. subcuneiformis [TA] SYN: subcuneiform n.. See reticular nuclei of mesencephalon.
- subhypoglossal n. [TA] a small bulbar n. lying immediately ventral (anterior) to the hypoglossal n.; considered one of the perihypoglossal nuclei. SYN: n. subhypoglossalis [TA].
- n. subhypoglossalis [TA] SYN: subhypoglossal n..
- n. subparabrachialis [TA] SYN: subparabrachial n..
- subparabrachial n. [TA] a cell group located ventral to the brachium conjunctivum in the general area where the medial and lateral parabrachial nuclei abut, shifting to the slightly more lateral position rostrally. SEE ALSO: parabrachial nuclei. SYN: n. subparabrachialis [TA].
- subthalamic n. [TA] a circumscript n., shaped like a biconvex lens, located in the ventral part of the subthalamus on the dorsal surface of the peduncular part of the internal capsule immediately rostral to the substantia nigra. The n. receives a massive topographic projection from the lateral segment of the globus pallidus and a somatopically organized projection from the ipsilateral motor cortex; a smaller bundle of afferents from the centromedian n. of the thalamus terminates in the rostral part of the n. The subthalamic n. projects to both pallidal segments, to the pars reticulata of the substantia nigra, and in a small way to the ipsilateral pedunculopontine n.. SYN: n. subthalamicus [TA], corpus luysi, Luys body, n. of Luys.
- n. subthalamicus [TA] SYN: subthalamic n..
- superior olivary n. [TA] a circumscript cell group located ventrolaterally in the lower pontine tegmentum, immediately dorsal to the trapezoid body; the n. receives fibers from the ipsilateral and contralateral cochlear nuclei, and contributes fibers to the lateral lemniscus of each side. It is prominently involved in the function of spatial localization of sound. The n. (also called the superior olivary complex) consists of a lateral superior olivary n. [TA] (n. olivaris superior lateralis [TA]), medial superior olivary n. [TA] (n. olivaris superior medialis [TA]), and the periolivary nuclei [TA] (nuclei periolivares [TA]), which are usually divided into medial nuclei [TA] and lateral nuclei [TA] (nuclei mediales [TA] and nuclei laterales [TA]). SYN: n. olivaris superior [TA], superior olivary complex.
- superior salivatory n. [TA] a group of preganglionic parasympathetic motor neurons situated rostral and lateral to the inferior salivatory n.; it governs secretion of the lacrimal, sublingual, and submaxillary glands by way of the facial nerve and the sphenopalatine and submandibular ganglia. SYN: n. salivatorius superior [TA], superior salivary n..
- superior vestibular n. [TA] n. vestibularis superior. See vestibular nuclei. SYN: n. vestibularis superior [TA].
- suprachiasmatic n. [TA] See anterior hypothalamic area.
- n. suprachiasmaticus [TA] small n. located dorsal to the optic chiasm; receives input from retina and influences hypothalamic neuroendocrine function; closely associated with regulation of circadian rhythmicity. SEE ALSO: anterior hypothalamic area.
- supralemniscal n. [TA] a small group of neurons located dorsal to the medial lemniscus and insinuated among the fibers of the ventral trigeminothalamic tract at mid to rostral levels of the pons. SYN: n. supralemniscalis [TA].
- n. supralemniscalis [TA] SYN: supralemniscal n..
- n. supramammillaris [TA] SYN: supramammillary n..
- supraoptic n. [TA] SYN: supraoptic n. [TA] of hypothalamus.
- supraoptic n. [TA] of hypothalamus a large-celled neurosecretory n. in the hypothalamus, located over the lateral border of the optic tract, from which the supraopticohypophysial tract arises; its neurons produce and transport vasopressin released into the general circulation from the axon terminals in the supraopticohypophysial tract. This n. can be divided into a pars dorsolateralis [TA], pars dorsomedialis [TA], and pars ventromedialis [TA]. SYN: n. supraopticus [TA], supraoptic n. [TA].
- n. supraopticus [TA] SYN: supraoptic n. [TA] of hypothalamus.
- n. tecti SYN: fastigial n..
- tegmental nuclei collective term for cell groups in the caudal midbrain and mid-to-rostral pons, one of which (ventral tegmental n.) is associated with the mammillary nuclei by way of the mammillary peduncle and mammillotegmental tract. Neurons in these nuclei are acetylcholinesterase-rich. The anterior tegmental n. [TA], also called the ventral tegmental n. [TAalt] (n. tegmentalis anterior [TA]), is located in the pontine tegmentum adjacent to the medial longitudinal fasciculus at the level of the trigeminal motor n.. The posterior tegmental n. [TA], also called the dorsal tegmental n. [TAalt], is located in the rostral pons in the area of the central gray substance. The lateroposterior tegmental n. [TA], also known as the laterodorsal tegmental n. [TAalt] (n. tegmentalis posterolateralis [TA]), is a larger cell group located partially in the central gray and partially ventrolateral to it at rostral pontine levels. The pedunculopontine tegmental n. [TA] (n. tegmentalis pedunculopontinus [TA]) is located in the rostral pons and caudal midbrain and consists of a compact part [TA] (pars compacta [TA] or compact subnucleus [TAalt]) and a dissipated part [TA] (pars dissipata [TA] or dissipated subnucleus [TAalt]. SYN: Gudden tegmental nuclei, nuclei tegmenti.
- n. tegmentalis pedunculopontinus [TA] SYN: pedunculopontine tegmental n.. See reticular nuclei of mesencephalon.
- nuclei tegmenti SYN: tegmental nuclei.
- terminal n., n. terminalis collective term indicating those nerve cell groups in the rhombencephalon and spinal cord in which the afferent fibers of the spinal and cranial nerves terminate. SYN: n. terminationis [TA], secondary sensory nuclei.
- n. terminationis [TA] SYN: terminal n..
- tetracyclic steroid n. the group of four fused rings forming the framework or parent substance of the steroids. SYN: perhydrocyclopenta[a]phenanthrene, steroid n..
- nuclei of trapezoid body [TA] small groups of neurons associated with the trapezoid body, forming the lateral n. of trapezoid body [TA] (n. lateralis corporis trapezoidei [TA]), medial n. of trapezoid body [TA] (n. medialis corporis trapezoidei [TA]), and the anterior n. of trapezoid body [TA] or ventral n. of trapezoid body [TA] (n. anterior corporis trapezoidei [TA]). These indistinct cell groups are involved in the relay of auditory input. SYN: nuclei corporis trapezoidei [TA].
- n. of trochlear nerve a group of motor neurons innervating the superior oblique muscle of the contralateral eye. The n. lies in the caudal half of the midbrain, behind the oculomotor n., in the most ventral part of the central gray substance, near the midline. SYN: n. nervi trochlearis [TA], trochlear n..
- trophic n. SYN: macronucleus (2).
- tuberal nuclei two or three small, encapsulated, round or ovoid clusters of cells in the lateral hypothalamic area along the surface of the tuber cinereum; their connections and functional significance are unknown. SYN: nuclei tuberales laterales [TA].
- nuclei tuberales laterales [TA] SYN: tuberal nuclei.
- n. tuberomammillaris [TA] SYN: tuberomammillary n..
- ventral anterior n. [TA] of thalamus the most rostral of the subdivisions of the ventral n., receiving projections from the globus pallidus and projecting to the premotor and frontal cortex. This n. is divisible into a magnocellular division [TA] (pars magnocellularis [TA]) and a principal division [TA] (pars principalis [TA]). SYN: n. ventralis anterior [TA].
- ventral intermediate n. [TA] of thalamus the composite middle third of the ventral n. receiving in its various parts distinctive projections from the contralateral half of the cerebellum (by way of the superior cerebellar peduncle) and the ipsilateral globus pallidus; nearly all parts of the n. project to the motor cortex. SYN: n. ventralis intermedius [TA], n. ventralis lateralis, ventral lateral n. of thalamus.
- n. ventralis posterior intermedius thalami intermediate part of the ventrobasal nuclear complex. See ventral posterior n. of thalamus. SYN: ventral posterior intermediate n. of thalamus.
- ventral lateral geniculate n. [TA] small cell group located rostral to the dorsal lateral geniculate n.. SYN: n. ventralis corporis geniculi lateralis [TA], pregeniculate n..
- ventral posterior intermediate n. of thalamus SYN: n. ventralis posterior intermedius thalami. See ventral posterior n. of thalamus.
- ventral posterolateral n. [TA] of thalamus, ventral posterior lateral n. of thalamus lateral part of the ventrobasal nuclear complex. See ventrobasal complex. SYN: n. ventralis posterolateralis [TA].
- ventral posteromedial n. [TA] of thalamus, posterior medial n. of thalamus medial part of the ventrobasal nuclear complex. See ventrobasal complex. SYN: n. ventralis posteromedialis [TA].
- ventral premammillary n. [TA] See posterior hypothalamic area. SYN: n. premammillaris ventralis [TA].
- ventral nuclei of thalamus [TA] a large, complex cell mass the external border of which forms the ventral and much of the lateral boundary, as well as the rostral border, of the thalamus; the nuclei making up this large area of the diencephalon are the ventral anterior n. [TA] (n. ventralis anterior [TA]), ventral lateral complex [TA] (nuclei ventrales laterales [TA]), ventral medial complex [TA] (nuclei ventrales medialis [TA]), ventral intermediate n. [TA] (n. ventralis intermedius [TA]), ventrobasal complex [TA] (nuclei ventrobasales [TA]), ventral posterior inferior n. [TA] (n. ventralis posterior internus [TA]), and ventral posterior parvocellular n. [TA] (n. ventroposterior parvocellularis [TA]). In general this area can be subdivided into an anterior, intermediate, and posterior part. SYN: nuclei ventrales thalami [TA].
- ventral tier thalamic nuclei collective term for nuclei in the ventral part of the lateral nuclear group, e.g., ventral anterior, lateral, posterolateral, and posteromedial nuclei and the medial geniculate nuclei and the dorsal lateral geniculate n.. The basoventral nuclear complex constitutes the caudal part of the ventral tier thalamic nuclei.
- ventral n. of trapezoid body a cell group embedded among the fibers of the trapezoid body, the major decussation of the central auditory pathway, in the lower pons. The n. receives fibers from the contralateral cochlear nuclei and contributes fibers to the ascending auditory system or lateral lemniscus.
- ventrobasal nuclei (complex) [TA] SYN: ventrobasal complex.
- nuclei ventrobasales [TA] SYN: ventrobasal complex.
- ventrolateral n. [TA] See anterior horn.
- ventromedial n. [TA] See intermediate hypothalamic area.
- ventromedial n. of hypothalamus [TA] a circumscript ovoid group of small neurons in the medial zone of the tuberal region of the hypothalamus. Bilateral destruction of this n. in the rat leads to severe obesity. It receives numerous fibers from the amygdala via the terminal stria; its efferent connections are obscure. SYN: n. ventromedialis hypothalami [TA].
- n. ventromedialis hypothalami [TA] SYN: ventromedial n. of hypothalamus. See intermediate hypothalamic area.
- vestibular nuclei [TA] a group of four main nuclei that are located in the lateral region of the hindbrain beneath the floor of the rhomboid fossa. These nuclei are the inferior vestibular n., medial vestibular n. (Schwalbe n.), lateral vestibular n. (Deiter n.), and superior vestibular n. (Bechterew n.). The inferior n. contains a group of large cells, the magnocellular part of inferior vestibular n. [TA] or cell group F [TAalt] (pars magnocellularis nuclei vestibularis inferioris [TA]), located caudally in the n.. A group of medium-sized neurons is located in lateral portions of the lateral n., the parvocellular part [TA] or cell group I [TAalt] (pars parvocellularis [TA]). These nuclei receive primary fibers of the vestibular nerve, are reciprocally connected with the flocculonodular lobe of the cerebellum, and project by way of the medial longitudinal fasciculus to the abducens, trochlear, and oculomotor nuclei and to the ventral horn of the spinal cord. The lateral vestibular n. projects to the ipsilateral ventral horn of the spinal cord by the vestibulospinal tract. SYN: nuclei vestibulares [TA].
- nuclei vestibulares [TA] SYN: vestibular nuclei.
- vestibulocochlear nuclei the combined cochlear and vestibular nuclei in the brainstem that receive the incoming fibers of the eighth cranial nerve. See vestibular nuclei. SYN: nuclei nervi vestibulocochlearis.
- nuclei viscerales nervi oculomotorii the visceral motor n. of the oculomotor nerve, also commonly called the Edinger-Westphal n., can be divided into an anterior medial n. [TA] (n. anteromedialis [TA]), and a posterior n. [TA] (n. dorsalis [TA]) SEE ALSO: Edinger-Westphal n..
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1) a cellular organelle of eukaryotes that is essential to cell functions (as reproduction and protein synthesis), is composed of nuclear sap and a nucleoprotein-rich network from which chromosomes and nucleoli arise, and is enclosed in a definite membrane
2) a mass of gray matter or group of nerve cells in the central nervous system
3) a characteristic and stable complex of atoms or groups in a molecule esp RING (2) <the naphthalene \nucleus>
4) the positively charged central portion of an atom that comprises nearly all of the atomic mass and that consists of protons and neutrons except in hydrogen which consists of one proton only
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n.
1. the part of a cell that contains the genetic material, DNA. The DNA, which is combined with protein, is normally dispersed throughout the nucleus as chromatin. During cell division the chromatin becomes visible as chromosome. The nucleus also contains RNA, most of which is located in the nucleolus. The nucleus is separated from the cytoplasm by a double membrane, the nuclear envelope.
2. an anatomically and functionally distinct mass of nerve cells within the brain or spinal cord.
3. the central part of the lens of the eye, which is harder than the outer cortex.
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nu·cle·us (nooґkle-əs) gen. and pl. nuґclei [L., dim. of nux nut] 1. the central core of a body or object. 2. cell nucleus: a spheroid body within a eukaryotic cell, separated from the cytoplasm by the nuclear envelope (which is penetrated by pores to allow communication with the cytoplasm), and containing chromatin, a nucleolus or nucleoli, and nucleoplasm. In the nucleus the cell's genetic information is stored on the chromosomes and RNA transcription and processing occur. 3. [TA] a group of nerve cells ordinarily located within the central nervous system and bearing a direct relationship to the fibers of a particular tract or system. 4. in organic chemistry, the combination of atoms forming the central element or basic framework of the molecule of a specific compound or class of compounds. 5. see atomic n.
Electron micrograph of a cell, showing the chromatin-rich nucleus bounded by the double-membraned nuclear envelope, the inner and outer membranes of which enclose the perinuclear space. The arrows point to nuclear pores.
Descriptions of anatomic structures are given on TA terms, and include anglicized names of specific nuclei.
Medical dictionary. 2011.