Bronnen bij Neurologie, cerebellum: artikelen

De meeste input is die van de mossy fibers - een naam die, zoals gewoonlijk in de neurologie, iets zegt over uiterlijk maar niets over functie. Mossy fibers komen binnen via de drie penducles: inferior, middle, en superior (beneden, midden en boven). Dat laatste zegt wel iets over functie, want inferior komt van medulla olongata en ruggemerg, middle van de pons, en superior

Het meeste daarvan komt van de cerebrale cortex, via de pons. Aan de pons zit de cerebral penducle, en van de pons via de middelste penducle naar het cerebellum.

en van de pons gaan onderste, middelste en bovenste penducles naar het cerebellum.

Mossy fibers are one of the major inputs to cerebellum. There are many sources of this pathway, the largest of which is the cerebral cortex, which sends input to the cerebellum via the pontocerebellar pathway. Other contributors include the vestibular nerve and nuclei, the spinal cord, the reticular formation, and feedback from deep cerebellar nuclei. Axons enter the cerebellum via the middle and rostral cerebellar peduncles, where some branch to make contact with deep cerebellar nuclei. They ascend into the white matter of the cerebellum , where each axon branches to innervate granule cells in several cerebellar folia.

In this case, the pathway is so named for a unique synapse formed by its projections, the mossy fiber rosette. Fine branches of the mossy fiber axons twist through the granule cell layer, and slight enlargements giving a knotted appearance indicate synaptic contacts. These contacts have the appearance of a classic Gray's type 1 synapse, indicating they are glutamatergic and excitatory. Sensory information relayed from the pons through the mossy fibers to the granule cells is then sent along the parallel fibers to the Purkinje cells for processing. Extensive branching in white matter and synapses to granular cells ensures that input from a single mossy fiber axon will influence processing in a very large number of Purkinje cells.

Please note: the text given below appears to deal with CEREBELLAR peduncles, not CEREBRAL peduncles (which is what this article is about). The two are completely unrelated.

Uncontrolled motor commands that only have Excitatory Postsynaptic Potentials (EPSPs) would produce uncoordinated, jerky and even spastic movements. To combat this, the brain uses the middle, superior and inferior peduncles in order to produce precise, fine controlled movement. When the cortex wants to send a command to the body, especially when concerning voluntary muscle movement, the command is first sent through the middle peduncle. At the same time, the spinal cord will send proprioceptive messages through the inferior peduncle. The sensory information concerning proprioception from the spinal cord will come from two afferent tracts, which are the "posterior (dorsal) and anterior (ventral) spinocerebellar".[2] The spinocerebellar tracts will "travel through the lateral column and carry proprioceptive signals from the limbs and trunk".[2] The information from the middle and inferior peduncles will then travel to the cerebellum. In the cerebellum, the correct amount of Inhibitory Postsynaptic Potential (IPSPs) will be added to the cortex's original command. The completed command will then leave the cerebellum through the superior peduncle and travel back to the cortex. Afterwards, the cortex will be able to send a finely controlled motor command for precise movement.

Van ieder van de DCN's zijn er twee.

interposed nucleus= globose nuclei en emboliform nuclei. receives its afferent supply from the anterior lobe of the cerebellum and sends output via the superior cerebellar peduncle to the red nucleus.

The Dentate nucleus is located within the deep white matter of each cerebellar hemisphere. It is the largest of the four deep cerebellar nuclei, the others being the fastigial nucleus and the interposed nucleus (globose and emboliform nuclei combined). It is responsible for the planning, initiation and control of volitional movements. It therefore receives its afferents from the premotor cortex and the supplementary motor cortex (via the pontocerebellar system). Its efferents project via the superior cerebellar peduncle through the red nucleus to the ventrolateral thalamus (crossing over at the pontomesencephalic junction).

It consists of an irregularly folded lamina, of a grayish-yellow color, containing white fibers, and presenting on its antero-medial aspect an opening, the hilus, from which most of the fibers of the superior peduncle emerge.




Inferior cerebellar peduncle

The upper part of the posterior district of the medulla oblongata is occupied by the inferior peduncle, a thick rope-like strand situated between the lower part of the fourth ventricle and the roots of the glossopharyngeal and vagus nerves.

Each cerebellar inferior peduncle connects the medulla spinalis and medulla oblongata with the cerebellum, and comprises the juxtarestiform body and restiform body.

Important fibers running through the inferior cerebellar peduncle include the spinocerebellar tract and axons from the inferior olivary nucleus, among others.

The inferior cerebellar peduncle carries many types of input and output fibers that are mainly concerned with integrating proprioceptive sensory input with motor vestibular functions such as balance and posture maintenance.

Proprioceptive information from the body is carried to the cerebellum via the posterior spinocerebellar tract.

This tract passes through the inferior cerebellar peduncle and synapses within the spinocerebellum (also known as the paleocerebellum).

Vestibular information projects onto the vestibulocerebellum (also known as the archicerebellum).

This peduncle also carries information directly from the Purkinje cells to the vestibular nuclei in the dorsal brainstem located at the junction between the pons and medulla oblongata.


The spinocerebellar tract is a set of axonal fibers originating in the spinal cord and terminating in the ipsilateral cerebellum. This tract conveys information to the cerebellum about limb and joint position (proprioception).


The olivocerebellar tract (olivocerebellar fibers) leaves the olivary nucleus and pass out through the hilum and decussate with those from the opposite olive in the raphé, then as internal arcuate fibers they pass partly through and partly around the opposite olive and enter the inferior peduncle to be distributed to the cerebellar hemisphere of the opposite side from which they arise.

They terminate directly on Purkinje cells as the climbing fiber input system

Olivospinal tract

The olivospinal fasciculus (Helweg) arises in the vicinity of the inferior olivary nucleus in the medulla oblongata, and is seen only in the cervical region of the medulla spinalis, where it forms a small triangular area at the periphery, close to the most lateral of the anterior nerve roots.


Climbing fibers

Climbing fibers are the name given to a series of neuronal projections from the inferior olivary nucleus located in the medulla oblongata.[1][2]

These axons pass through the pons and enter the cerebellum via the inferior cerebellar peduncle where they form synapses with the deep cerebellar nuclei and Purkinje cells. Each climbing fiber will form synapses with 1-10 Purkinje cells.

Early in development, Purkinje cells are innervated by multiple climbing fibers, but as the cerebellum matures, these inputs gradually become eliminated resulting in a single climbing fiber input per Purkinje cell.

These fibers provide very powerful, excitatory input to the cerebellum which results in the generation of complex spike excitatory postsynaptic potential (EPSP) in Purkinje cells.[1] In this way climbing fibers (CFs) perform a central role in motor behaviors.[3]

Climbing fiber activation is thought to serve as a motor error signal sent to the cerebellum, and is an important signal for motor timing.

These climbing fibers carry information from various sources such as the spinal cord, vestibular system, red nucleus, superior colliculus, reticular formation and sensory and motor cortices.


Inferior olivary nucleus

It is closely associated with the cerebellum, meaning that it is involved in control and coordination of movements[1], and likely also sensory processing and cognitive tasks especially the timing of sensory input[2], [3].

There is some evidence that it is stimulated by ghrelin.[4]

[edit] Anatomy
It consists of a gray folded lamina arranged in the form of an incomplete capsule, opening medially by an aperture called the hilum.

Emerging from the hilum are numerous fibers that collectively constitute the peduncle of the olive. The axons, also known as olivocerebellar fibers, leave the olivary nucleus, exit through the hilum, and decussate with those from the opposite olive in the raphe.

Then, as internal arcuate fibers, they pass partly through and partly around the opposite olive and enter the inferior peduncle to be distributed to the cerebellar hemisphere of the opposite side from which they arise.

The fibers are smaller than the internal arcuate fibers connected with the medial lemniscus.

Fibers passing in the opposite direction from the cerebellum to the olivary nucleus are often described as the CTT, but their existence is doubtful.

Much uncertainty exists also with regard to the connections of the olive and the spinal cord.

Important connections between the cerebrum and the olive of the same side exist, but the exact pathway is unknown.

Many collaterals from the reticular formation and from the pyramids enter the inferior olivary nucleus.

Removal of one cerebellar hemisphere is followed by atrophy of the opposite olivary nucleus.

Middle cerebellar peduncle

The middle cerebellar peduncles (brachia pontis) are composed entirely of centripetal fibers, which arise from the cells of the nuclei pontis of the opposite side and end in the cerebellar cortex; the fibers are arranged in three fasciculi, superior, inferior, and deep.

The superior fasciculus, the most superficial, is derived from the upper transverse fibers of the pons; it is directed backward and lateralward superficial to the other two fasciculi, and is distributed mainly to the lobules on the inferior surface of the cerebellar hemisphere and to the parts of the superior surface adjoining the posterior and lateral margins.
The inferior fasciculus is formed by the lowest transverse fibers of the pons; it passes under cover of the superior fasciculus and is continued downward and backward more or less parallel with it, to be distributed to the folia on the under surface close to the vermis.
The deep fasciculus comprises most of the deep transverse fibers of the pons. It is at first covered by the superior and inferior fasciculi, but crosses obliquely and appears on the medial side of the superior, from which it receives a bundle; its fibers spread out and pass to the upper anterior cerebellar folia. The fibers of this fasciculus cover those of the restiform body.

Superior cerebellar peduncles

The superior cerebellar peduncles (brachium conjunctivum), two in number, emerge from the upper and medial part of the white substance of the hemispheres and are placed under cover of the upper part of the cerebellum.

They are joined to each other across the middle line by the anterior medullary velum, and can be followed upward as far as the inferior colliculi, under which they disappear.

Below, they form the upper lateral boundaries of the fourth ventricle, but as they ascend they converge on the dorsal aspect of the ventricle and thus assist in roofing it in.

All fibers (except vestibular fibers to the vestibular nuclei through the inferior cerebellar peduncle) carrying information from the cerebellum to the midbrain and pons pass through the superior cerebellar peduncle.


Pontine nuclei

The pontine nuclei are a part of the pons which store the memory of intention during motor activity. Corticopontine fibres carry information from the primary motor cortex to the ipsilateral pontine nucleus in the ventral pons, and the pontocerebellar projection then carries that information to the contralateral cerebellum via the middle cerebellar peduncle.

They therefore allow modification of actions in the light of their outcome, or error correction, and are hence important in learning motor skills.


Brain: Inferior colliculus

The inferior colliculus (IC) (Latin, lower hill) is the principal midbrain nucleus of the auditory pathway and receives input from several more peripheral brainstem nuclei in the auditory pathway, as well as inputs from the auditory cortex.[1] The inferior colliculus has three subdivisions: the central nucleus (CIC), a dorsal cortex (DCIC) by which it is surrounded, and an external cortex (ICX) which is located laterally.[2] Its bimodal neurons are implied in auditory-somatosensory interaction, receiving projections from somatosensory nuclei. This multisensory integration may underlie a filtering of self-effected sounds from vocalisation, chewing, or respiration activities.[3]

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24 jul.2010