Cerebellum Flashcards
vestibular pathway to cerebellum
vestibular nerve gives rise to afferent fibers that terminate in the vestibular nuclei in brainstem -> give rise to mossy fibers that pass through the inferior cerebellar peduncle to enter the ipsilateral flocculonodular lobe on same side
Cortical projections destined for the cerebellum first project to what three brainstem structures
pontine nuclei, inferior olivary nuclei and reticular formation
input and output for pontocerebellum
input: contralateral cerebral cortex to pontine nuclei (corticopontine fibers) -> cross midline and enter cerebellum via MCP
output: Purkinje cells to dentate nucleus -> cross in superior cerebellar peduncle-> thalamus (VL, VPL, centrolateral) -> primary motor cortex -> lateral corticospinal tract -> decussation -> ipsilateral coordination
efferent cerebellar fiber pathway to the thalamus involves what deep cerebellar nuclei
dentate
Functional organization of the cerebellum
1) vestibulocerebellum
2) spinocerebellum
3) pontocerebellum
vestibulocerebellum
- composed primarily of the flocculonodular lobe
- afferent fibers = mossy fibers from ipsilateral vestibular nuclei and vestibular ganglion via inferior cerebellar peduncle
- also receives visual information from LGB, superior colliculus and striate cortex
- efferent -> purkinje cells project to fastigial nucleus -> inferior cerebellar peduncle to vestibular nuclei -> vestibulospinal tract
function of cuneocerebellar tract
proprioceptive information from upper limb and upper part of the thorax
What are the interposed nuclei
globose and emboliform
what does PICA supply in the cerebellum?
inferior vermis, cerebellar tonsil, inferior cerebellar peduncle, inferolateral cerebellar hemisphere
output from the cerebellum is transmitted by what cells
Purkinje cells (inhibitory)
fibers of the inferior cerebellar peduncel
afferent
- -dorsal spinocerebellar tract
- cuneocerebellar tract
- olivocerebellar tract
- reticulocerebellar tract
- vestibulocerebellar tract
efferent
-fastigial nucleus projections
Foramen of Magnendie
median aperture, constitutes an opening in the inferior medullary velum that opens 4th ventricle into cisterna magna
efferent fiber pathway to red nucleus involves what deep cerebellar nuclei?
globose and emboliform
Neurotransmitter for all the cells in the cerebellar cortex
1) Granule cells -> glutamate
2) Purkinje cells -> GABA
3) stellate cells -> GABA
4) Golgi cells -> GABA
5) basket cells -> GABA
input and output of spinocerebellum
input: dorsal and ventral spinocerebellar tracts
- also information from auditory, visual and vestibular systems
output: Purkinje cells (vermis) to fastigial nucleus -> brainstem reticular formation, lateral vestibular nucleus and primary motor cortex
Purkinje cells (intermediate) -> globose and emboliform nuclei -> red nucleus -> rubrospinal tract and lateral corticospinal tract
efferent cerebellar pathway that projects to vestibular nuclei involves what deep cerebellar nucleus?
fastigial
Medial to lateral: list the deep cerebellar nuclei
fastigial, globose, emboliform, and dentate
components of the spinocerebellum
vermis and intermediate part of the cerebellar hemisphere
How are climbing fibers and mossy fibers modulated?
through stellate, basket and Golgi cells. All of these cells are inhibitory (GABA).
fibers of the middle cerebellar peduncle
afferent:
-contralateral pontocerebellar fibers
Embryonic cerebellar layer
AKA external granule layer; present during the prenatal and early post-natal periods but is completely gone by 1st year of life
efferent cerebellar pathway to red nucleus
axons from globose and emboliform -> superior cerebellar peduncle -> CROSS MIDLINE -> synapse in contralateral red nucleus -> projects fibers via crossed rubrospinal tract -> therefore crossed twice to remain ispilateral -> influence flexor activity of the extremities
Efferents for each deep cerebellar nuclei
1) fastigial -> exit via the inferior cerebellar peduncle to the brainstem
2) all others -> exit via the superior cerebellar peduncle to cerebral cortex and brainstem
corticoreticulocerebellar pathway
BILATERAL projections to the reticular formation of the pons and medulla -> MOSSY FIBERS enter IPSILATERAL cerebellar hemisphere via inferior and middle cerebellar peduncle
How many cerebellar fissures?
two
1) primary -> separates anterior lobe from the posterior lobe on the superior surface
2) dorsolateral fissure -> separates posterior lobe form the flocculonodular lobe on inferior surface
efferent cerebellar pathway to thalamus
dentate -> superior cerebellar peduncle -> crosses midline -> contralateral VENTROLATERAL/VENTROPOSTEROLATERAL/ CENTROLATERAL NUCLEI -> axons to internal capsule and corona radiata -> terminate in primary motor cortex ->influences motor neurons in cerebral cortex on contralateral side -> cortex then projects corticospinal tract -> decussates in medulla -> THEREFORE dentate nucleus influences motor activities on the same side of the body (coordination of the ipsilateral body)
Dorsal spinocerebellar tract
originates in nucleus dorsalis (Clarkes column) -> UNCROSSED FIBERS enter the cerebellum via INFERIOR CEREBELLAR PEDUNCLE -> terminates as mossy fibers
The only excitatory afferent fiber system in the cerebellum?
Granule cells
fastgial fiber pathway
exit cerebellum via inferior cerebellar peduncle -> terminate on LATERAL VESTIBULAR NUCLEUS BILATERALLY -> fibers descend uncrossed as the descending vestibulospinal tract -> influence extensor tone on the same side of the body
destinations of efferent fibers from cerebellum
1) red nucleus
2) thalamus
3) vestibular complex
4) reticular formation
spinal cord projections to cerebellum from what strucutures?
1) ventral spinocerebellar tract
2) dorsal spinocerebellar tract
3) cuneocerebellar tract
cuneocerebellar tract
originates in the accessory cuneate nucleus of the medulla -> upper extremity equivalent of the dorsal spinocerebellar tract -> enters cerebellar hemisphere via INFERIOR CEREBELLAR PEDUNCLE
Mossy fiber pathway
indirectly influence a large number of Purkinje cells by branching extensively in the granule cell layer -> synaptic contacts with the granule cells and Golgi type II cell bodies -> granule cells then project to the molecular layer where they bifurcate in a T shape manner to form PARALLEL FIBERS -> each of which snaps with large number of Purkinje cell dendrites
What spinocerebellar tract is the only tract to enter the cerebellum through the superior cerebellar peduncle?
ventral spinocerebellar tract
climbing fiber pathway
inferior olive -> direct contact with dendrites on a limited number of Purkinje cells
components of the cerebellar molecular layer
dendrites of Pukinje cells from the Purkinje layer and axons of granule cells; synaptic layers; +/- stellate and basket cells
Corticopontocerebellar pathway
cortex -> corona radiata -> internal capsule -> pontine nuclei -> MOSSY FIBERS THAT CROSS MIDLINE TO REACH OPPOSITE CEREBELLAR HEMISPHERE VIA MIDDLE CEREBELLAR PEDUNCLE
Efferent (output) from the cerebellum exits via..
superior and inferior (fastigial) cerebellar peduncles
How many lobes does the cerebellum have?
3 lobes:
1) anterior lobe (paleocerebellum)
2) posterior lobe (neocerebellum)
3) flocculonodular lobe (archicerebellum)
Name the 5 cell types in the cerebellar cortex
stellate, basket, Purkinje, Golgi and granule cells
origin of climbing fibers
inferior olive
Two afferent fibers for the cerebellum
climbing fibers and mossy fibers
How many layers to the cerebellar cortex?
Three
1) Molecular layer (outermost)
2) Pukinje layer
3) Deep Granular layer (innermost)
function of dorsal spinocerebellar tract
proprioceptive information from one side of the body (trunk and lower limbs) to cerebellum ipsilaterally
ventral spinocerebellar tract
originates in ventral and intermediate gray matter of spinal cord -> fibers cross midline to enter ventral spinocerebellar tract contra laterally -> enters the cerebellum via SUPERIOR CEREBELLAR PEDUNCLE -> CROSSES AGAIN FOR 2ND TIME -> IPSILATERAL CEREBELLAR HEMISPHERE AS MOSSY FIBERS
The embryonic cerebellar layer is thought to be the cell of origin for what tumor?
medulloblastomas
function of the spinocerebellum
regulate axial and proximal musculature; execution of movement and regulates muscle tone (flexor); gets feedback from reticular nuclei and corrects deviations from intended movement
The synaptic connection between a mossy fiber and a granule cell is called a
Rosette
Purkinje fibers located lateral hemisphere and vermis project to what deep cerebellar nuclei?
Lateral -> dentate
vermis -> fastigial
in between -> globose and emboliform
what does the AICA supply in the cerebellum?
flocculus, part of the dentate nucleus, inferior cerebellar hemisphere, choroid plexus of the 4th ventricle
what does the superior cerebellar artery supply in the cerebellum?
superior vermis, superior cerebellar peduncle, deep nuclei, superior medullary velum, superior surface of the cerebellar hemisphere
Input to the deep cerebellar nuclei
2 sources
1) excitatory input from fibers that originate in cells that lie outside the cerebellum
2) inhibitory input from fibers that arise from the Purkinje cells of the cortex
cortico-olivocerebellar pathway
cortex -> corona radiata -> internal capsule -> terminates BILATERALLY in inferior olivary nucleus -> CLIMBING FIBERS THAT CROSS MIDLINE TO ENTER OPPOSITE CEREBELLAR HEMISPHERE VIA INFERIOR CEREBELLAR PEDUNCLE
What tracts outside the cerebellum send fibers to the deep cerebellar nuclei?
Pontocerebellar, spinocerebellar, and olivocerebellar
function of the pontocerebellum
concerns volitional movements that are ongoing or are about to happen
what is the function of the ventral spinocerebellar tract
mainly proprioceptive information from one side of the body (lower limbs) to the same side of the cerebellum
Where do the Purkinje cells project to?
Deep cerebellar nuclei (dentate, fastigial, emboliform and globose)
Cerebellar Granular cell layer
consists of densely packed neurons that send axonal projections into the molecular layer; composed of Granule cell and Golgi Cells
What forms the rostral and caudal aspects of the roof of the fourth ventricle?
rostral -> superior cerebellar peduncles
caudal -> inferior medullar velum
function of vestibulocerebellum
concerned with adjustment of axial muscle tone and maintenance of equilibrium, as well as plays a role in eye movements, control and coordination of head and eye movements (via MLF)
fibers of the superior cerebellar peduncle
afferent:
-ventral spinocerebellar tract
efferent
-outputs from dentate, globose and emboliform nuclei
