atomic nucleus


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nucleus

 [noo´kle-us] (pl. nu´clei) (L.)
1. cell nucleus; a spheroid body within a cell, contained in a double membrane, the nuclear envelope, and containing the chromosomes and one or more nucleoli. The contents are collectively referred to as nucleoplasm. The chromosomes contain deoxyribonucleic acid (DNA), which is the genetic material that codes for the structure of all the proteins of the cell.
2. a mass of gray matter in the central nervous system, especially such a mass marking the central termination of a cranial nerve.
3. 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.
4. the dense core of an atom, made of protons and neutrons held together by the strong nuclear force. Traveling in orbit around it is a cloud of negatively charged particles called electrons. The number of protons in the atomic nucleus gives a substance its identity as a particular element. Called also atomic nucleus. adj., adj nu´clear.
The nucleus and nucleolus of a cell. From Mahon and Manuselis, 2000.
nucleus ambi´guus the nucleus of origin of motor fibers of the glossopharyngeal, vagus, and accessory nerves in the medulla oblongata.
nucleus an´sae lenticula´ris (nucleus of ansa lenticularis) a collection of neurons in the ansa lenticularis as it curves around the medial edge of the globus pallidus.
arcuate nuclei of medulla oblongata, nu´clei arcua´ti medul´lae oblonga´tae small irregular areas of gray substance on the ventromedial aspect of the pyramid of the medulla oblongata.
atomic nucleus nucleus (def. 3).
basal nuclei (nu´clei basa´les) specific interconnected subcortical masses of gray matter embedded in each cerebral hemisphere and in the upper brainstem, comprising the corpus striatum (caudate and lentiform nuclei), amygdaloid body, claustrum, and external, extreme, and internal capsules. Called also basal ganglia.
caudal olivary nucleus a folded band of gray substance enclosing a white core, which produces the elevation on the medulla oblongata known as the olive.
caudate nucleus (nucleus cauda´tus) an elongated, arched gray mass closely related to the lateral ventricle throughout its entire extent, which, together with the putamen, forms the neostriatum.
nucleus ceru´leus a compact aggregation of pigmented neurons lying below the locus ceruleus.
cochlear nuclei, anterior and posterior the nuclei of termination of sensory fibers of the cochlear nerve (see anatomic Table of Nerves in the Appendices); they partly encircle the inferior cerebellar peduncle at the junction of the medulla oblongata and pons.
dentate nucleus (nucleus denta´tus) the largest of the deep cerebellar nuclei, lying in the white matter of the cerebellum just lateral to the emboliform nucleus.
droplet nuclei small particles of pathogen-containing respiratory secretions expelled into the air by coughing, which are reduced by evaporation to small, dry particles that can remain airborne for long periods; one possible mechanism for transmission of infection from one individual to another.
emboliform nucleus (nucleus embolifor´mis) a small cerebellar nucleus lying between the dentate nucleus and the globose nucleus and contributing to the superior cerebellar peduncles.
fastigial nucleus (nucleus fasti´gii) the most medial of the deep cerebellar nuclei, near the midline in the roof of the fourth ventricle.
globose nucleus (nucleus globo´sus) a cerebellar nucleus lying between the emboliform nucleus and the nucleus fastigii and projecting its fibers via the superior cerebellar peduncle.
intracerebellar nuclei four accumulations of gray matter embedded in the white matter of the cerebellum, comprising the dentate nucleus, emboliform nucleus, nucleus fastigii, and globose nucleus.
lenticular nucleus (lentiform nucleus) the part of the corpus striatum somewhat resembling a biconvex lens, divided into a larger external or lateral part called the putamen and a smaller light colored internal or medial part called the globus pallidus.
motor nucleus any collection of cells in the central nervous system giving origin to a motor nerve.
olivary nucleus a folded band of gray matter that encloses a white core and produces the elevation called the olive on the medulla oblongata; it receives heavy projections from the spinal cord, mesencephalon, and cerebral cortex and projects fibers via the contralateral inferior cerebellar peduncle.
nuclei of origin, nu´clei ori´ginis groups of nerve cells in the central nervous system from which arise the motor, or efferent, fibers of the cranial nerves.
paraventricular nucleus (nucleus paraventricula´ris) a band of cells in the wall of the third ventricle in the supraoptic part of the hypothalamus; many of its cells are neurosecretory in function and project to the neurohypophysis, where they secrete oxytocin (and, to a lesser extent, antidiuretic hormone).
pontine nuclei, nu´clei pon´tis masses of nerve cells scattered throughout the ventral part of the pons, in which the longitudinal fibers of the pons terminate, and whose axons in turn cross to the opposite side and form the middle cerebellar peduncle, which projects fibers to the neocerebellum.
nucleus pro´prius a column of large neurons that extends throughout the posterior horn of the spinal cord.
nucleus pulpo´sus (pulpy nucleus) a semifluid mass of fine white elastic fibers forming the center of an intervertebral disk.
red nucleus (nucleus ru´ber) an oval mass of gray matter (pink in fresh specimens) in the anterior part of the tegmentum and extending into the posterior part of the hypothalamus; it receives fibers from the cerebellum.
sensory nucleus the nucleus of termination of the afferent (sensory) fibers of a peripheral nerve.
supraoptic nucleus (nucleus supraop´ticus) one just above the lateral part of the optic chiasm; many of its cells are neurosecretory in function and project to the neurohypophysis, where they secrete antidiuretic hormone (ADH) and, to a lesser extent, oxytocin; other cells are osmoreceptors that stimulate ADH release in response to increased osmotic pressure.
tegmental nucleus, laterodorsal several nuclear masses of the reticular formations of the pons and midbrain, especially of the latter, where they are in close approximation to the superior cerebellar peduncles.
thoracic nucleus (nucleus thora´cicus) thoracic column.
vestibular nuclei, nu´clei vestibula´res the four cellular masses in the floor of the fourth ventricle: superior (rostral or cranial), lateral, medial, and inferior (caudal) vestibular nuclei; in them are the terminations of the branches of the vestibular nerve (see anatomic Table of Nerves in the Appendices). The nuclei give rise to a widely dispersed special sensory system through projections to motor nuclei in the brain stem and cervical cord, to the cerebellum, and to motor cells throughout the spinal cord; they also have connections that provide for conscious perception of, and autonomic reactions to, labyrinthine stimulation.

a·tom·ic nu·cle·us

(ă-tomik nūklē-ŭs)
Centralized portion of the atom; composed of protons and neutrons.

atomic nucleus

In chemistry, the heavy, positively charged, central part of an atom, which contains protons, neutrons, and most of the atomic mass.
Synonym: nucleus (4)
See also: nucleus

nucleus

pl. nuclei [L.]
1. cell nucleus; a spheroid body within a cell, contained in a double membrane, the nuclear envelope, and containing the chromosomes and one or more nucleoli. The contents are collectively referred to as nucleoplasm. The chromosomes contain deoxyribonucleic acid (DNA), which is the genetic material that codes for the structure of all the proteins of the cell.
2. a mass of gray matter in the central nervous system, especially such a mass marking the central termination of a cranial nerve.
3. 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.
4. the dense core of an atom; called also atomic nucleus. It is made of protons and neutrons held together by the strong nuclear force. Traveling in orbit around the nucleus is a cloud of negatively charged particles called electrons. The number of protons in the atomic nucleus gives a substance its identity as a particular element (2).

nucleus abducens
located in the floor of the fourth ventricle; its axons constitute the abducent nerve.
nucleus ambiguus
the nucleus of origin of motor fibers of the glossopharyngeal, vagus and accessory nerves that supply the striated muscle of the pharynx and larynx. Found in the medulla oblongata.
arcuate nucleus, nucleus arcuati
small irregular areas of gray substance on the ventromedial aspect of the pyramid of the medulla oblongata.
atomic nucleus
nucleus (3).
basal nucleus
large brain nuclei, the caudate and lentiform nuclei, which combine with the white matter to form the corpus striatum. Important in the regulation of motor function.
caudate nucleus, nucleus caudatus
an elongated, arched gray mass closely related to the lateral ventricle throughout its entire extent, which, together with the putamen, forms the neostriatum.
central nervous system nucleus
aggregations of neurons within the brain.
cerebellar nucleus
there are a number of them; they are surrounded by the medulla oblongata caudal to the cerebellum.
cochlear nucleus (dorsal and ventral)
the nuclei of termination of sensory fibers of the cochlear part of the vestibulocochlear (eighth cranial) nerve, which partly encircle the inferior cerebellar peduncle at the junction of the medulla oblongata and pons.
cranial nerve nucleus
aggregations of cell bodies associated with the cranial nerves, which in general are organized as continuations of the four gray matter components of the spinal cord plus three others which appear in the medulla oblongata developed for innervation of the organs in the head.
cuneate nucleus
medial and lateral nuclei are situated in the medulla oblongata.
dentate nucleus, nucleus dentatus
the largest of the deep cerebellar nuclei lying in the white matter of the cerebellum.
Edinger-Westphal nucleus
located in the midbrain and a center for coordination of oculomotor activity.
facial nucleus
in the medulla oblongata and the origin of the facial nerve.
gracile nucleus
located in the medulla oblongata.
habenular nucleus
the gray matter of the habenula.
hypoglossal nucleus
located in the medulla oblongata, the origin of the hypoglossal nerve.
lateral geniculate nucleus
concerned in the transmission of visual stimuli.
lenticular nucleus, lentiform nucleus
the part of the corpus striatum just lateral to the internal capsule, comprising the putamen and globus pallidus.
medial geniculate nucleus
a nucleus within the thalamus; involved in transmission of auditory stimuli.
motor nucleus
any collection of cells in the central nervous system giving origin to a motor nerve.
oculomotor nucleus
the cells of the midbrain which make up the origin of the oculomotor nerve.
olivary nucleus, nucleus olivaris
1. a folded band of gray matter enclosing a white core and producing the elevation (olive) on the medulla oblongata.
2. olive (2).
nucleus of origin
any collection of nerve cells giving origin to the fibers, or a part of the fibers, of a peripheral nerve.
paraventricular nucleus, nucleus paraventricularis
a band of cells in the wall of the third ventricle in the supraoptic part of the hypothalamus; many of its cells are neurosecretory in function and project to the neurohypophysis, where they secrete oxytocin (and, to a lesser extent, antidiuretic hormone).
pontine nucleus, nucleus pontis
groups of nerve cell bodies in the part of the pyramidal tract within the ventral part of the pons, upon which the fibers of the corticopontine tract synapse, and whose axons in turn cross to the opposite side and form the middle cerebellar peduncle.
pulpy nucleus, nucleus pulposus
a semifluid mass of fine white and elastic fibers forming the center of an intervertebral disk. It serves to distribute pressure over the vertebral body. It shows early age changes, may calcify and herniate through the fibrous rings that enclose it to cause disk disease.
red nucleus
an oval mass of gray matter (pink in fresh specimens) in the anterior part of the tegmentum and extending into the posterior part of the hypothalamus; one of the important relay stations in the extrapyramidal motor pathway of the CNS; origin of the rubrospinal tract in the cord; called also nucleus ruber.
nucleus ruber
see red nucleus (above).
salivatory nucleus
groups of preganglionic parasympathetic neurons concerned with salivary secretion organized into a rostral nucleus, of the facial nerve, and the caudal nucleus, of the glossopharyngeal nerve.
sensory nucleus
the nucleus of termination of the afferent (sensory) fibers of a peripheral nerve.
supraoptic nucleus, nucleus supraopticus
one just above the lateral part of the optic chiasm; many of its cells are neurosecretory in function and project to the neurohypophysis, where they secrete antidiuretic hormone (ADH) and, to a lesser extent, oxytocin; other cells are osmoreceptors that stimulate ADH release in response to increased osmotic pressure.
tegmental nucleus
several nuclear masses of the reticular formations of the pons and midbrain, especially of the latter, where they are in close approximation to the superior cerebellar peduncles.
thoracic nucleus, nucleus thoracicus
a column of cells in the dorsal gray column of the spinal cord, extending from the seventh or eighth cervical segments to the second or third lumbar level.
trapezoid body nucleus
a relay station in the auditory pathways.
trigeminal nucleus
there are three sensory nuclei and one motor nucleus of the trigeminal nerve found in the brainstem; the sensory nuclei comprise the mesencephalic nucleus, the nucleus of the descending tract, and the principal sensory nucleus, but none is exclusive to the trigeminal nerve, all of them receiving sensory inputs from other cranial nerves.
trochlear nucleus
source of the trochlear nerve; located in the tegmentum of the midbrain.
vagus nucleus
source of the vagus nerve.
vestibular nucleus, nucleus vestibularis
the four cellular masses (superior, lateral, medial and inferior) in the floor of the fourth ventricle, in which the branches of the eighth cranial (vestibulocochlear) nerve terminate.
References in periodicals archive ?
The study reveals a novel arrangement of matter made of quarks, the basic constituents of Lambda (1405) and every atomic nucleus in the universe.
An atomic nucleus consists of both protons and neutrons, and the advantage of using the nuclear spin as a qubit is that the nucleus is well protected, and nearly impervious to unwanted electromagnetic disturbance, which is a condition for keeping the sensitive information in the qubit intact.
They are typically composed of several thousand atoms and the atom's electrons are shared and coordinated as if there is only one atomic nucleus at the centre.
The story, which has fascinated the author since boyhood, begins with the 1909 discovery of the atomic nucleus, sometimes compared in its relation to the atom to a fly in a cathedral.
Dr Krausz said: "As you go into smaller structures of matter - inside the atomic nucleus - processes become even faster.
But hinting at findings to come, he added: 'As you go into smaller structures of matter, inside the atomic nucleus, processes become even faster.
Around 15bn years ago the entire universe was compressed into the confines of an atomic nucleus.