Internal capsule

Internal capsule
Horizontal section of right cerebral hemisphere. (Capsula interna labeled at upper left.)
The motor tract.
Details
Identifiers
Latin	capsula interna
NeuroNames	hier-180
NeuroLex ID	Internal capsule
TA	A14.1.09.524
FMA	61950
Anatomical terms of neuroanatomy []

The internal capsule is a white matter structure situated in the inferomedial part of each cerebral hemisphere of the brain. It carries information past the basal nuclei, separating the caudate nucleus and the thalamus from the putamen and the globus pallidus. The internal capsule contains both ascending and descending axons. The internal capsule contains fibres going to and coming from the cerebral cortex.

The corticospinal tract constitutes a large part of the internal capsule, carrying motor information from the primary motor cortex to the lower motor neurons in the spinal cord. Above the basal nuclei the corticospinal tract is a part of the corona radiata, below the basal nuclei the tract is called crus cerebri (a part of the cerebral peduncle) and below the pons it is referred to as the corticospinal tract.

The internal capsule is V-shaped when cut horizontally, in a transverse plane.

When cut horizontally:

The genu is the flexure of the internal capsule. It is formed by fibers from the corticonuclear tracts. The fibers in this region are named the geniculate fibers; they originate in the motor part of the cerebral cortex and, after passing downward through the base of the cerebral peduncle with the cerebrospinal fibers, undergo decussation and end in the motor nuclei of the cranial nerves of the opposite side. It contains the corticobulbar tract, which carries upper motor neurons from the motor cortex to cranial nerve nuclei that mainly govern motion of striated muscle in the head and face.