Medical term:

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]

Farlex Partner Medical Dictionary © Farlex 2012

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.

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]

Medical Dictionary for the Health Professions and Nursing © Farlex 2012

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.

Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005

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

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]

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