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The interposed nucleus is the combined paired
globose This glossary of botanical terms is a list of definitions of terms and concepts relevant to botany and plants in general. Terms of plant morphology are included here as well as at the more specific Glossary of plant morphology and Glossary ...
and emboliform nuclei, ( deep cerebellar nuclei) on either side of the
cerebellum The cerebellum (: cerebella or cerebellums; Latin for 'little brain') is a major feature of the hindbrain of all vertebrates. Although usually smaller than the cerebrum, in some animals such as the mormyrid fishes it may be as large as it or eve ...
. It is located in the roof of the fourth ventricle, lateral to the
fastigial nucleus The fastigial nucleus (roof nucleus-1) is located in each cerebellar hemisphere. It is one of the four paired deep cerebellar nuclei of the cerebellum. It is made up of two sections: the rostral fastigial nucleus and the caudal fastigial nucle ...
. The emboliform nucleus is the ''anterior interposed nucleus'', and the globose nucleus is the ''posterior interposed nucleus''. The interposed nucleus is responsible for coordinating agonist/antagonist muscle pairs, and therefore a lesion in this area causes
tremor A tremor is an involuntary, somewhat rhythmic muscle contraction and relaxation involving neural oscillations, oscillations or twitching movements of one or more body parts. It is the most common of all involuntary movements and can affect the h ...
.


Anatomy

The interposed nucleus is located in the paravermis of the cerebellum. The interposed nucleus is smaller than the dentate but larger than the fastigial nucleus.


Afferents

The interposed nuclei receives Purkine cell terminal afferents from the paravermal cortex of the
spinocerebellum The anatomy of the cerebellum can be viewed at three levels. At the level of gross anatomy, the cerebellum consists of a tightly folded and crumpled layer of Cerebellar cortex, cortex, with white matter underneath, several deep nuclei embedded i ...
, as well as collaterals of cerebellar afferents from the restiform body and
ventral spinocerebellar tract The spinocerebellar tracts are nerve tracts originating in the spinal cord and terminating in the same side ( ipsilateral) of the cerebellum. The two main tracts are the dorsal spinocerebellar tract, and the ventral spinocerebellar tract. Both of ...
. It receives input from the ipsilateral posterior external arcuate fibers (cuneocerebellar tract) and the
dorsal spinocerebellar tract The spinocerebellar tracts are nerve tracts originating in the spinal cord and terminating in the same side ( ipsilateral) of the cerebellum. The two main tracts are the dorsal spinocerebellar tract, and the ventral spinocerebellar tract. Both of ...
, which originate in the accessory cuneate nucleus and the posterior thoracic nucleus, respectively.


Efferents

Afferents from the interposed nuclei leave the cerebellum through superior cerebellar peduncle. They project to: * contralateral (magnocellular division of) the
red nucleus The red nucleus or nucleus ruber is a structure in the rostral midbrain involved in motor coordination. The red nucleus is pale pink, which is believed to be due to the presence of iron in at least two different forms: hemoglobin and ferritin. ...
(→
rubrospinal tract The rubrospinal tract is one of the descending tracts of the spinal cord. It is a motor control pathway that originates in the red nucleus. It is a part of the lateral indirect extrapyramidal tract. The rubrospinal tract fibers are efferent ne ...
). The red nucleus is the main target of tne interposed nuclei. * ipsilateral ventral lateral nucleus of thalamus (→
premotor cortex The premotor cortex is an area of the motor cortex lying within the frontal lobe of the brain just anterior to the primary motor cortex. It occupies part of Brodmann's area 6. It has been studied mainly in primates, including monkeys and human ...
and
primary motor cortex The primary motor cortex ( Brodmann area 4) is a brain region that in humans is located in the dorsal portion of the frontal lobe. It is the primary region of the motor system and works in association with other motor areas including premotor c ...
lateral corticospinal tract Lateral is a geometric term of location which may also refer to: Biology and healthcare * Lateral (anatomy), a term of location meaning "towards the side" * Lateral cricoarytenoid muscle, an intrinsic muscle of the larynx * Lateral release ( ...
). The rubrospinal and lateral corticospinal tracts are subsequently involved in control of the distal musculature of the extremities.


Function

The interposed nucleus modulates muscle stretch reflexes of proximal limb muscles, and is also required in delayed Pavlovian conditioning.


References


External links

* https://web.archive.org/web/20080405060224/http://www.lib.mcg.edu/edu/eshuphysio/program/section8/8ch6/s8ch6_30.htm * http://www.neuroanatomy.wisc.edu/cere/text/P5/interp.htm Cerebellum {{neuroanatomy-stub