thalamus

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thalamus

 [thal´ah-mus] (L.)
either of two large ovoid structures (the dorsal thalamus or simply thalamus and the ventral thalamus) composed of gray matter and located at the base of the cerebrum. (See also brain.) adj., adj thalam´ic. The thalamus functions as a relay station in which sensory pathways of the spinal cord and brainstem form synapses on their way to the cerebral cortex. Specific locations in the thalamus are related to specific areas on the body surface and in the cerebral cortex. A sensory impulse from the body surface travels upward to the thalamus, where it is received as a primitive sensation and then is sent on to the cerebral cortex for interpretation as to location, character, and duration. The thalamus has numerous connections to other areas of the brain as well, and these are thought to be important in the integration of cerebral, cerebellar, and brainstem activity.
ventral thalamus the subthalamic tegmental region, a transitional region of the diencephalon interposed between the (dorsal) thalamus, the hypothalamus, and the tegmentum of the mesencephalon; it includes the subthalamic nucleus, Forel's fields, and the zona incerta. Called also subthalamus.

thal·a·mus

, pl.

thal·a·mi

(thal'ă-mŭs, -mī), [TA]
The large, ovoid mass of gray matter that forms the larger dorsal subdivision of the diencephalon; it is placed medial to the internal capsule and the body and tail of the caudate nucleus. Its medial aspect forms the dorsal half of the lateral wall of the third ventricle; its dorsal surface can be subdivided into a lateral triangle forming the floor of the body (central part) of the lateral ventricle, and a medial triangle covered by the velum interpositum; its taillike caudal part curves ventralward around the posterolateral aspect of the cerebral peduncle and ends in the lateral geniculate body. The thalamus is composed of a large number of anatomically and functionally distinct cell groups or nuclei, usually classified as 1) sensory relay nuclei (ventral posterior nucleus and lateral and medial geniculate body), each receiving a modally specific sensory conduction system and in turn projecting each to the corresponding primary sensory area of the cortex; 2) "secondary" relay nuclei (ventral intermediate nucleus and ventral anterior nucleus) receiving fibers from the medial segment of the globus pallidus, the contralateral deep cerebellar nuclei (that is, cerebellothalamic fibers), and the pars reticulata of the substantia nigra that project to various regions of the motor cortex; 3) a nucleus associated with the limbic system, for example, the composite anterior nucleus receiving the mammillothalamic tract and projecting to the fornicate gyrus; 4) association nuclei (medial dorsal nucleus and lateral nucleus including the large pulvinar), each projecting to a particular large expanse of association cortex; or 5) the midline and intralaminar nuclei or "nonspecific" nuclei (centromedian nucleus, central lateral nucleus, paracentral nucleus, and nucleus reuniens).
See also: dorsal thalamus.
[G. thalamos, a bed, a bedroom]

thalamus

/thal·a·mus/ (thal´ah-mus) pl. thal´ami   [L.] either of two large ovoid masses, consisting chiefly of gray substance, situated one on either side of and forming part of the lateral wall of the third ventricle. Each is divided into dorsal and ventral parts; the term thalamus without a modifier usually refers to the dorsal thalamus, which functions as a relay center for sensory impulses to the cerebral cortex.
optic thalamus  lateral geniculate body.

thalamus

(thăl′ə-məs)
n. pl. thala·mi (-mī′)
A large ovoid mass of gray matter situated in the posterior part of the forebrain that relays sensory impulses to the cerebral cortex.

tha·lam′ic (thə-lăm′ĭk) adj.

thalamus

[thal′əməs] pl. thalami
Etymology: Gk, thalamos, chamber
one of a pair of large oval nervous structures made of gray matter and forming most of the lateral walls of the third ventricle of the brain and part of the diencephalon. It relays sensory information, excluding smell, to the cerebral cortex. It is composed mainly of gray substance and translates impulses from appropriate receptors into crude sensations of pain, temperature, and touch. It also participates in associating sensory impulses with pleasant and unpleasant feelings, in the arousal mechanisms of the body, and in the mechanisms that produce complex reflex movements. Compare epithalamus, hypothalamus, subthalamus. thalamic, adj.

thal·a·mus

, pl. thalami (thal'ă-mŭs, -mī) [TA]
The large, ovoid mass of gray matter that forms the larger dorsal subdivision of the diencephalon; it is placed medially to the internal capsule and the body and tail of the caudate nucleus. Its medial aspect forms the dorsal half of the lateral wall of the third ventricle; its dorsal surface can be subdivided into a lateral triangle forming the floor of the body (central part) of the lateral ventricle, and a medial triangle covered by the velum interpositum; its taillike caudal part curves ventralward around the posterolateral aspect of the cerebral peduncle and ends in the lateral geniculate body.
[G. thalamos, a bed, a bedroom]

thalamus

One of two masses of grey matter lying on either side of the midline in the lower part of the brain. It receives sensory nerve fibres from the spinal cord and connections from the midbrain, the eyes, the ears and the cerebral CORTEX. It sends fibres to the sensory part of the cerebral cortex. It is the collecting, coordinating and selecting centre for almost all sensory information, other than OLFACTORY, received by the body. Only part of the mass of information it receives is passed to the cortex. From the Greek thalamos, an inner chamber.

thalamus

the major sensory coordinating part of the vertebrate forebrain, consisting of two egg-shaped masses of grey matter within the cerebral hemispheres. The thalami act as relay points for all sensory signals entering the brain.

Thalamus

A large oval area of gray matter within the brain that relays nerve impulses from the basal ganglia to the cerebellum, both parts of the brain that control and regulate muscle movement.
Mentioned in: Neurologic Exam, Tremors

thalamus

dorsal subdivision of diencephalon; thalamic nuclei include sensory relay nuclei (relaying incoming sensory information to sensory cortex), secondary relay nuclei (projecting to central motor cortex), limbic system nucleus, association nuclei, midline nuclei and habenula

thalamus 

One of a pair of ovoid masses of grey substance that serves as a relay station for sensory stimuli to the cerebral cortex. It contains the lateral geniculate body, which is a continuation of the pulvinar and which is situated at the posterior end of the thalamus. See lateral geniculate bodies.

thal·a·mus

, pl. thalami (thal'ă-mŭs, -mī) [TA]
The large, ovoid mass of gray matter that forms the larger dorsal subdivision of the diencephalon; it is placed medially to the internal capsule and the body and tail of the caudate nucleus.
[G. thalamos, a bed, a bedroom]

thalamus (thal´əmus),

n an ovoid mass in the brain immediately lateral to the third ventricle that serves as the principal relay and integration station for the sensory systems in the body.
thalassemia
n a hereditary, chronic, hemolytic anemia with erythroblastosis. A complex of hereditary disorders characterized by microcytosis and increased red blood cell destruction and often associated with abnormal hemoglobins and increased normal trace hemoglobins. These disorders are prevalent in people of Mediterranean, African, and Asian ancestry. Disorders include Cooley's anemia, Cooley's trait, hemoglobin H disease, Hb S-thalassemia, Hb Cthalassemia, and Hb E-thalassemia.
thalassemia major (Cooley's anemia, erythroblastic anemia, famil-ial erythroblastic anemia, hereditary microcytosis, Mediterranean anemia, Mediterranean disease),
n the severe homozygous form of thalassemia characterized by a marked microcytic hypochromic anemia, atypical nucleated red blood cells, marked increase in hemoglobin F, and skeletal changes (underdevelopment, mongoloid facies, anterior open bite).
thalassemia minor (Cooley's trait),
n a heterozygous form of thalassemia that is a carried state with relatively mild manifestations; α2 hemoglobin is elevated.

thalamus

pl. thalami [L.] either of two large ovoid structures composed of gray matter and situated at the base of the cerebrum.
The thalamus functions as a relay station in which sensory pathways of the spinal cord and brainstem form synapses on their way to the cerebral cortex. Specific locations in the thalamus are related to specific areas on the body surface and in the cerebral cortex. A sensory impulse from the body surface travels upward to the thalamus, where it is received as a primitive sensation and then is sent on to the cerebral cortex for interpretation as to location, character and duration.
The thalamus has numerous connections to other areas of the brain as well, and these are thought to be important in the integration of cerebral, cerebellar and brainstem activity.