Cerebellum

cerebellum functions

motor part of brain

maintains equilibrium and coordinates muscle contractions

contributes to synergy of muscle action

ensures that contraction of the proper muscles occurs at the appropriate time, each with correct force

classic cerebellar deficits

ataxic, wide-based, unsteady gait

dysdiadochokinesia

difficulty with accurate movement - decomposition of movement, dysmetria, intention tremor

structural features

vermis

hemispheres

anterior, posterior lobes

folia

what does the cerebellum consist of ?

surface layer - cortex

gray matter - in transverse folds/folia

white matter - central body

what are the 3 layers in the cerebellum?

molecular layer, Purkinje later, granule layer

how many pairs of central nuclei are there? where are they located?

four pairs

embedded in deep cerebellar white matter

what nucleus has to do with precise movements?

dentate nucleus

where does cerebellar output come from?

deep nuclei

what connects the cerebellum with the brain stem?

3 pairs of cerebellar peduncles (composed of myelinated axons)

1. superior cerebellar - outflow of info, crosses to ventrolateral thalamus (VL) then to cerebral cortex

2. middle cerebellar - inflow of proprioceptive info

3. inferior cerebellar - both inflow and outflow (made up of restiform body and juxtarestiform)

what is the dentate of the cerebellum?

the center of the cerebellum, contain deep nuclei that send collaterals to the cerebellar cortex

deep nuclei are in constant ______. The cerebellar cortex has primarily a _____ effect.

excitation, have constant inflow of information

inhibitory

the main mass of the cerebellum consists of ____ and ____ except for ______.

anterior lobe, posterior lobe, flocculonodular lobe

the anterior lobe is the part of the superior surface ___ to the primary fissure

rostral

the cerebellar surface is folded into many narrow folia with __% of the cortical surface concealed in the intervening sulci

the cortical area is about ___ the size of the cerebral cortex

85

3/4

molecular cell layer

synaptic zone, contains the dendrites of the Purkinje cells which branch profusely in a plane perpendicular to the long axis of the folium

contains axons of granule cells, dendrites of Purkinje cells, basket and stellate cells (inhibitory)

Purkinje cell layer

consists of a single row of bodies of Purkinje cells, large principal cells of the cerebellar cortex

Purkinje cells contains the output of the cerebellar cortex (use GABA - inhibitory)

granule cell layer

deep to the layer of Purkinje cells, contains closely packed interneurons with axons that extend into the molecular layer

other cerebellar interneurons have their cells bodies in the molecular and granular layers

granule cell is the only excitatory cell

what are parallel fibers?

axons of the granule cells that run in th elong axis of the folium in the molecular layer

each parallel fiber is in a position to contact several Purkinje cells (because Purkinje cells have dendrites in plane perpendicular to folium)

what is the primary excitatory cell of the cortex?

granule

golgi cell

dendrites branch in molecular layer, have an axon that is inhibitory to granule cell

basket cell

located in molecular layer, axons form a “basket” around the Purkinje cell bodies; inhibitory (GABA)

what are the only axons that leave the cortex?

Purkinje cells, they terminate in central nuclei of the cerebellum (except some fibers from cortex of flocculonodular lobe that go to vestibular nuclei in brainstem)

what are climbing fibers?

originate in the inferior olivary complex of nuclei and synapse with the proximal parts of the dendritic trees of Purkinje cells - excite Purkinje cells and nucleus

what are mossy fibers?

endings of cerebellar afferents from other sources, they synapse with neurons in the granular layer in formation known as glomerulus that excites granule and golgi cells

what do mossy fibers do?

send collaterals to the central cerebellar nuclei and are excitatory

what are the 4 pairs of nuclei in the cerebellar white matter?

fastigial, globose, emboliform, dentate (medial to lateral)

what are the input to the cerebellar nuclei?

sources outside of the cerebellum, Purkinje cells of the cortex

the extrinsic input of the cerebellar nuclei consists of?

pontocerebellar, spinocerebellar, olivocerebellar fibers

most of these afferents are collateral branches of fibers proceeding to the cerebellar cortex

what is the composition of the inferior peduncle

afferent: olivocerebellar fibers (climbing), dorsal spinocerebellar tract (mossy), cuneocerebellar tract (mossy), vestibulocerebellar (mossy), trigeminal sensory nuclei (mossy)

efferent: cerebellar corticovestibular, cerebelloreticular fibers

what is the composition of middle peduncle?

afferent: pontocerebellar fibers (mossy)

what is the composition of the superior peduncle?

afferent: ventral spinocerebellar tract (mossy), trigeminothalamic (mesencephalic) (mossy), rostral spinocerebellar tract (mossy)

efferent: cerebellothalamic from cerebellar nuclei to VL of contralateral thalamus, cerebellorubral fibers to ipsilateral red nucleus

archicerebellum =

paleocerebellum =

neocerebellum =

vestibulocerebellum

spinocerebellum

pontocerebellum

what lobe is the vestibulocerebellum? what input does it receive?

flocculonodular lobe

receives input from vesitibular nerve and nuclei

some of these afferents synapse on the fastigial nucleus

the vestibulocerebellum influences motor neurons through?

vestibulospinal tract

medial longitudinal fasciculus

reticulospinal fibers

it is concerned with adjustment of muscle tone in response to vestibular stimuli

coordinates actions of muscles that maintain equilibrium and participates in other motor responses, including those of the eyes, to vestibular stimulation

the spinocerebellum consists of? what terminates here?

vermis and anterior lobe with adjacent medial or paravermal zones of the hemispheres

spinocerebellar and cuneocerebellar fibers (proprioceptive/sensory info)

the spinocerebellum gets input from?

anterior and posterior spinocerebellar, cuneocerebellar, olivocerebellar, these fibers synapse on fastigial, globose, emboliform nuclei on way to cortex

what does output of spinocerebellum control?

axial musculature through vermal cortex and fastigial efferents - postural corrections

limb musculature through efferents of the globose and emboliform nuclei (locomotion)

what does the pontocerebellum comprise of? afferents are from?

large lateral parts of the hemispheres and superior vermis in the posterior lobe

contralateral pontine nuclei

pontocerebellum gets input from?

contralateral pontine nuclei

pontocerebellar fibers make up the whole MCP

fibers synapse with dentate nucleus on way to cerebellar cortex

efferents from the dentate nucleus terminate in the VL of thalamus

VL projects to cerebral cortex (M1)

cortex of cerebellar hemisphere receives information concerning volitional movements (anticipated or in progress) via the..

corticopontine and pontocerebellar projections

some of the pontine nuclei receive afferents from ____ and relay data used by the cerebellum in the control of what visually guided movements

superior colliculus

decomposition of movements

breakdown of movement into individual components (ipsilateral)

ataxia

unsteady gait, wide-based gait, tendency to fall to side of lesion (ipsilateral)

dysmetria

past-pointing, tend to move past or short of an object when trying to point at it (ipsilateral)

tremor

intention tremor, finger to nose more difficult as the finger approaches the nose; no tremor at rest (ipsilateral)

dysdiadochokinesia

difficulty with rapid alternating movements (ipsilateral)

blood supply to cerebellum?

superior cerebellar a.

basilar a

AICA

PICA

vertebral a

anterior spinal a