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8/17/2019 Anat 6.6 Cerebellum_Deriada
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Anatomy 6.6 February 14, 2012
Cerebellum Dr. Maj Deriada
Group 3A |Cy, CARA, Cring, Kenji Page 1 of 11
OUTLINEI. CEREBELLUM
A. GrossB. Function
II. DIVISIONS AND ORGANIZATION
A.
Lobes (Transverse Division)B. Longitudinal Zones (Sagittal Division)C. Organization
III. CEREBELAR CORTEX: CELL LAYERSA. Molecular LayerB. Purkinje LayerC. Granular LayerD. Inner White Matter
IV. IMPORTANT SYNAPSES AND CIRCUITRYA. Synaptic OrganizationB. Patterns of Excitation
V. NEURONS AND FIBERS OF THE CEREBELLUMA. Three HighwaysB. Three Inputs
C.
Three OutputsVI. CEREBELLAR AFFERENT FIBERSA. From the CortexB. From the Spinal CordC. From the Vestibular Nerve
VII. CEREBELLAR EFFERENT FIBERSVIII. SUMMARY (CEREBELLAR CORTICAL CIRCUITRY)IX. CLINICAL CORRELATIONS
Objectives: Name the major lobes of the cerebellum and give the function of each
lobe. Describe the division of the cerebellum into a midline vermis and lateral
cerebellar hemispheres. Describe the histology of the cerebellar cortex. Name the deep cerebellar nuclei and their general connections. Name the types of afferent fibers to the cerebellar cortex and identify
their source. Name the afferent fibers from the cerebellar cortex. Trace the various circuitries within the cerebellar cortex. Name the cerebellar peduncles and the fiber tracts (afferent and efferent)
that constitute them. Describe the cerebellar connections of the vestibular system.
References Snell’s Neuroanatomy Lansang’s Neuroananatomy Notes Dr. Deriada’s Slide Lecture
LegendsText in Times New Roman are from reference books and 2014B trans
Text in Arial Narrow are from the recorded lecture of Dr. DeriadaText in Calibri are from the powerpoint presentation of the lectures
I. CEREBELLUM
A. GROSS
Located in the posterior cranial fossa roof over by a vault of dura matter separating from occipital lobe of
cerebrum (tentorium cerebelli) lies posterior to the pons and medulla oblongata
is ovoid in shape with 2 lateral rounded cerebellar hemisphere thpinched in the middle by the vermis
fiber tracts called cerebellar peduncle connecting it to the midbrainmedulla
o Superior Cerebellar peduncle (brachium conjunctivum)midbrain
o Middle Cerebellar peduncle (B. Pontis) ponso Inferior (restiform body) medulla
The medial part is the juxtarestiform body
B. FUNCTION
Coordination of voluntary muscle activity [maintaining fine ancomplex]
Equilibrium Muscle tonus
o [Helps maintain posture and maintain equilibrium while walking running; execute sequential movement like writing, putting buttons and brushing teeth and as well as rapidly, alternating anrepetitive movement.]
o Controls muscular movement ipsilateral or same side of the bounlike cerebrum
The cerebellum has no direct PW to the LMN’s Exerts its control via the cerebral cortex and the brainstem Does not initiate movement; regulation A person with lesion on the cerebellum WILL NOT be paralyzed but
have disorganized, uncoordinated, slow and tremulous movement in teye and limb movements
There will be problem in muscle tone and posture- either hyper tonushypotonus; and when standing or walking he would or stagger or swayin
II. DIVISIONS AND ORGANIZATION
A. LOBES (Transverse division) LOBES (transverse division)- divided by a transverse plane: givingrise to Anterior, Posterior and Flocculonodular lobe
Fig. 1 Cerebellar Lobes in Transverse View. Take note of the fissures.
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AnatomicDivision
ANTERIOR POSTERIOR ORMIDDLE(Largest)
FLOCCULONODULAR
FunctionalDivision
Spinocerebellum Cerebrocerebellum Vestibulocerebellum
PhylogeneticDivision
Paleocerebellum Neocerebellum Archicerebellum(oldest)
Gross Location Situated anterior toprimary fissure andterminates at rostralend of cerebellum
Posterior to theprimary fissure andanterior lobe.Limited by theposterolateral fissure
With a pair of flocculusand at the vermis thereis a nodulus (pl. Flocculiand noduli)
Between anterior and
posterior lobeFissure Primary Fissure-
wide v-shapedepression orlongitudinal fissurethat separatesanterior and posteriorlobe
PosterolateralFissure- separateposterior lobe fromflocculonodular lobe
Input Spinocerebellarandtrigeminocerebellar pathways
Cerebral cortex Vestibular nuclei
Function Stance and gait Speech andcoordinatedmovement
Equilibrium (balance,posture and eyemovements)
Three fissures of cerebellum:
1. Primary Fissure2. Posterolateral or Uvulonodular Fissure3. Horizontal Fissure- no significance and demarcates the superior
and inferior surfaces of the cerebellum
TONSILS ON THE NEOCEREBELLUMIn the neocerebellum there is a pair of tonsils (located at both side of the midline).When ICP increase like of tumor may cause herniation through the foramenmagnum because it immediately lies to it, compressing the brainstem which isessential for breathing and blood pressure
B. LONGITUDINAL ZONES (Sagittal Division)
Section made through the cerebellum parallel to the median planedivides the folia at right angles and the cut surface has a branched
appearance called Arbor vitae.
This gives rise to the functional areas of the cerebellar cortex
VERMIS INTERMEDIATE LATERAL
Medial LateralSynonymous
termVERMALFLOCCULONODULAR ZONE
PARAVERMAL
Direction ofprojection
fibers
To spinal cord
[efferent fibers:fastigialnucleus synapse axon tovestibularnuclei SC long axis of thebody]
To cerebralhemisphere[includes anteriorlobe and the anteriorpart of vermis]
[singals/ informationfrom cereberalcortext to emboliformand globose nuclei ornucleus interposidus
axonsterminated
contralateral rednucleus crossingthe other side of thespinal cord]
[MOSTLYPOSTERIOR part]
[cerebral cortex dendate nuclei thalamus motorcortex pontinenuclei and anteriorhorn of spinalcord]
Function Control ofposture, muscletone,locomotion andequilibrium
spinal cord andlimbs [particularlyof hands and feet]
Therebyresponsible forSTANCE AND GAIT
Coordination ofipsilateralsomatic motoractivity
Planning ofmovements
Assessment oferrors
Damage/Disease/Lesion
Ataxia-uncoordinatedvoluntarymuscularmovements
Wide-based stanceStagger walking Cerebellarincoordination(asynergia- lackof coordination.Ergoincoordination )
Dysmetria- refersto a lack ofcoordination ofmovement typified
by the undershootor overshoot ofintended positionwith the hand, arm,leg, or eye.Inability to judgedistance or scale
Past-pointing
Tremors
Dysdiadochokinesis- inability toperform regular/rapidlyalternatingmovementsReboundphenomenon
Fig. 2 Cerebellar Zones.
C. Organization Outer layer of gray matter- cortex Inner core of white matter
o Fold in cerebellum or folia would contain outer cortex and inner cwhite matter
Deep in the white matter are four pairs of masses of gray matteror the intracerebellar nuclei:
o Large, multipolar neurons; simple branching dendrites; andAxons
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1. Dentate nucleus - largest, most lateral2. Emboliform nucleus - ovoid and situated medial to dentate3. Globose nucleus - small, rounded in pairs or single4. Fastigial nucleus - the most medial on the sides of midline
The collection of globose and emboliform nucleus forms asINTERPOSED NUCLEI or NUCLEUS INTERPOSIDUS
Fig. 3 Location of the Nucleus Interpositus
III. CEREBELAR CORTEX: CELL LAYERSThe cerebellar cortex can be regarded as a large sheet with foldslying in the coronal plane. Each fold or folium contains a core ofwhite matter covered superficially by gray matter. The gray matter of the cortex throughout its extent has a
uniform structure. It may be divided into 3 layers:1. Molecular layer External
2. Purkinje cell layer Middle
3. Granular layer Internal
Fig.4 Cerebellar cortex layers.
A. Molecular Layer
Contains two types of neurons: (1) outer: stellate cell (2) inner:basket cell that are scattered among dendritic arborizationsand numerous thin axons running parallel to the folia.
Neuroglial cells are found in between
B. Purkinje Cell Layer
Purkinje cells - large, flask-shaped Golgi type 1 neuron arrangedin a single layer
The cell body of the purkinje cells lie in the purkinje cell layerwhile the dendrites pass into the molecular layer where theyundergo profuse branching
The primary and secondary branches of the dendrites aresmooth
Dendritic spines- short and thick spines that cover thesubsequent branches which form synaptic contacts with theparallel fibers derived from granule cell axons
Axons of the purkinje cells will project into the granular layerand will acquire myelin sheath and terminate by synapsing with
the cells of one of the intracerebellar nuclei which will form thecerebellar peduncle.
Collateral branches synapse with dendrites of the basket andstellate cells.
Some pass directly to the end in the vestibular nuclei of thebrainstem. They by-pass the intracerebellar nuclei.
The axons of these cells are the ENTIRE OUTPUT FIBERS of thecerebellar cortex.
Purkinje cells form the center of a functional unit of thecerebellar cortex
C. Granular Layer
Found between purkinje cell layer and the cerebellar white matter . Packed small cells with densely staining nuclei and scanty
cytoplasm It has three structures. Each give rise to 4-5 dendrites whichmake claw-like endings synapsing with mossy fiber output1. Granule cells- smallest neurons in the body2. Golgi Cells- scattered throughout and dendrites reach
molecular layer3. Cerebellar glomeruli/cerebellar island
Cerebellar glomeruli are capped by glial cells which contain:1. Mossy fiber rosette2. Terminals of golgi type II axons3. Dendrites terminal of granular cell
Dendrites synapse with mossy fiber output Axons pass into the molecular layer where it bifurcates in a T-
junction forming parallel fibers that run at right angles and
synapse with dendritic processes of the purkinje cells Neuroglial cells are found throughout
Fig. 5 Photomicrograph of a cross-section of the folia showing the layers ofthe cerebellar cortex
IV. INNER WHITE MATTERThere is a large amount of white matter in each cerebellarhemisphere. The white matter is made up of three groups offibers: (1) intrinsic, (2) afferent, and (3) efferent
Intrinsic fibers- located in the cerebellum but connect differentregions of the organ. Within in the cerebellum only.
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Afferent fibers- form the greater part of the white mattercoming from the cerebral cortex and proceed to cerebellarcortex; enter the cerebellum mainly to inferior and middlecerebellar peduncle.**MIDDLE CEREBELLAR PEDUNCLE ONLY CONTAINS AFFERENTFIBERS.
Efferent fiber- OUTPUT of cerebellum; commence as the axonsof the Purkinje cell and synapse with deep cerebellar nuclei.** most of purkinje cell axons in flocculonodular lobe and vermisefferent fibers leave cerebellum via juxtarestiform body w/o
synapsing in any cerebellar nucleiV. IMPORTANT SYNAPSES AND CIRCUITRY
A. SYNAPTIC ORGANIZATION PURKINJIE CELLS
- Output cells of the cortex inhibit neurons of theunderlying deep cerebellar nuclei.
- The inhibitory control of Purkinje cells over theexcitability of the deep cerebellar nuclei is a key aspectof cerebellar function.
EXCITATORY1. Mossy fibers: enter the cerebellum from the spinal cord,
pontine nuclei, vestibular ganglia and nuclei, trigeminalnuclei, and reticular formation nucleio Glutamate (except those from the pedunculopontine
nucleus and some of the vestibular nuclei – Ach)2. Climbing fibers: originate exclusively in the inferior olive
o Glutamate and Aspartate (excite the purkinje celldendrites on which they synapse)
o GABA:inhibit the deep cerebellar nuclei Inhibitory : noradrenergic (locus ceruleus superior
cerebellar peduncle), dopaminergic (substantia nigra& ventral mesencephalic tegmentum nucleusinterpositus and dentate nuclei), and serotonergic(raphe nuclei all parts of the cerebelar nuclei andcortex
OTHER CELLS: INHIBITORY1. Basket cells
o Inhibit the Purkinje neurons; synapse with climbingfibers and purkinje dendrites
2. Stellate cellso inhibit the Purkinje neurons; synapse with climbing
fibers and purkinje dendriteso Golgi – inhibits granule cell
B. PATTERNS OF EXCITATION Both mossy and climbing fibers input produce excitatory effects
in both the deep cerebellar nuclei and cortex 1. Mossy fiber input: indirectly – activates the granule cells
(through their axonal processes, the parallel fibers) and theiraxonso Ends of all other afferent cerebellar tracts (except the
olivocerebellar tract)o Have multiple brancheso Exert much more diffuse excitatory effecto A single mossy fiber can stimulate thousands of Purkinje
cells through the granule cells
o Terminate at the granular layer to form the cerebellarisland
o 1 mossy fiber: 20 granule cell dendriteso 1 mossy fiber synapse with golgi neurons
A. Granule cells excite purkinje, basket, stellateand golgi type ii
B. Basket & stellate inhibit purkinje and golgi typeii
C. Golgi type ii inhibit granule cells D. Purkinje cells, the only route for all information
exiting from the cerebellar cortex, inhibit thedeep cerebellar and vestibular nuclei.Consequently, within it, only the granule cellscause excitation.
MOSSY FIBERS CIRCUITRY:*(+) = excitatory synapses *(-) = inhibitory synapseso Mossy fiber (+) Granule cell axon (Parallel
fiber) to (+) Golgi cell axon to (-) Granulecell
o Mossy fiber (+) Granule cell axon (Parallelfiber) to (+) :
2. Climbing fiber input: directlyo Directly synapse with the dendrites of Purkinje cells
(molecular layer) o Terminal fibers of the olivocerebellar tractso Pass through the granular layer of the cortex and
terminate in the molecular layer by dividing repeatedly (T- junction forming parallel fibers that run at right angles tothe dendritic processes of the purkinje cells)
o One climbing fiber makes contact with 1 to 10 Purkinjeneurons
o Synapse with cells: (collaterals) Purkinje Golgi Type II Basket cells Stellate cells
CLIMBING FIBERS CIRCUITRY:Climbing fiber (+) Dendrites of Purkinje cell axon to (-) Dentate nucleus
o Dendrite of Purkinje cell Axon to (-) Deepcerebellar nuclei
o Dendrite of Basket cell Axon to (-) Purkinje cell ataxon hillock
o Dendrite of Stellate cell Axon to (-) Purkinje cell
*Purkinje Cell = Functional Unit Sole output neuron of the cerebellar cortex
It will accept excitatory impulses but in return, as it formsit axon, its output is inhibitory. Where modulation and regulation of impulses occur
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Fig. 6 Perpendicular arrangement of parallel fibers to purkinje cells
Fig. 7 Cerebellar Cortex Circuitry
*Excitatory climbing and mossy fibers use GLUTAMATE as excitatorytransmitter on the dendrites of the Purkinje cells. Other afferent
fibers entering the cortex liberate NOREPINEPHRINE ANDSEROTONIN at their endings that possibly modify the action of theglutamate on the Purkinje cells.
V. NEURONS AND FIBERS OF THE CEREBELLUM Afferent fibers
a. Climbing Fibers -arise ONLY from olivocerebellar afferent pathway frominferior olive nucleus into superior cerebellar peduncle
b. Mossy Fibers- Terminal fibers of all other cerebellar afferent fibers
- synapses with golgi neurons- influence the degree of purkinje cell stimulationproduced by climbing and mossy fiber input
Efferent Fibers: neuron location and synapsesNeuron Cell body
LocationDendrites Location Axons Location
PurkinjeFibers
Purkinjelayer
Molecular layersynapsing withparallel fiber/axonsof granule cell and
Granular layerextending to whitematter and synapsewith deep cerebellar
climbing fibers nuclei to inhibit themSmallgranulesCells
Granularlayer
Granular layer andsynapse with axonsof Golgi type II andmossy fibers
Molecular layer andbifurcates to formparallel fibers. Theysynapse with dendritesof purkinje, basket,stellate and golgi type IIcells
GolgiType IIcells
Granularlayer
Molecular layer andsynapse with mossyfibers
Granular layer andsynapse with mossyfiber and small granule
dendrites
VI. CEREBELLAR CORTEX CIRCUITRY
A. THREE HGHWAYS
1. Superior Cerebellar Peduncle Midbrain (Brachosyncytium) Afferent :
o Ventral spinocerebellar Tract (unconscious)o Some trigeminocerebellar Fibers
Efferent (*largest cerebellar efferent bundle):o Projections from the cerebellar cortex originate
from the dentate nucleuso Origin of most efferent fibers from lateral
cerebellar hemisphere (most fibers) to form: Dentatorubral Tract Dentatothalamic Tract Dentatoreticular Tract
NOTE: These tracts cross in the lower midbrain level as thedecussation of the superior cerebellar peduncle
2. Middle Cerebellar Peduncle Pons (Brachiobodies) Afferent ONLY :
o Pontocerebellar Tract (Cross tract / Contralateral)
3. Inferior Peduncle Medulla (Lentiform bodies) Mainly afferent Afferent :
o Dorsal Spinocerebellar Tracto Cuneocerebellar Tracto Reticulocerebelllar Tracto Olivocerebellar Tract (important) o Trigeminocerebellar Fibers (some)o Vestibulocerebellar Fibers
Efferent :o Fastigiobulbar Tract
Juxtarestiform body to Vestibular Nuclei
B. THREE INPUTS
1. Mossy Fibers Spinocerebellar pathways
o Ends in the granular layer
2. Climbing Fibers From the inferior olive Ends in the molecular layer
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3. More Mossy Fibers From the pons, which are carrying information from the
cerebral cortex
C. THREE OUTPUTS1. Fastigial Nuclei
Concerned with balance; sends information mainly tothe vestibular and reticular nuclei (Medial)
Receives purkinje cell output from the vermal zone,send efferent fibers to the reticular and vestibular nucleiof the brainstem project into the spinal cord control of posture and balance
2. Interposed Nuclei Same as dentate nucleus; Globose + Emboliform Receives input from purkinje cell in the paravermal and
vermal zone magnocellular division of the rednucleus rubrospinal tract crosses midline anddescend into the SC. – locomotion and coordinatedmovements of the extremities
3. Dentate Nuclei Concerned more with voluntary movement and send
axons mainly to the thalamus and red nucleus (lateral &biggest)
OTHER EFFERENTSo Lateral zone
Lateral part of the posterior lobe send purkinje cellaxon dentate and interposed nucleus
Fibers from the dentate nucleus terminate in theparvocellular division of the red nucleus rubro-olivarytract descend ipsilaterally terminate in the inferiorolivary complex feedback to the dentate and lateralzone
o Thalamocortical fibers Ventral lateral thalamic nucleus motor regions of the
ipsilateral frontal lobe o Intralaminar nuclei
Prefrontal cortex executive functioning Parietal lobe visuospatial processing Frontal lobe linguistic activity Cingulate and parahippocampal region affective and
motivational phenomena
SOURCE TERMINATION PEDUNCLE USEDDentate Nucleus-voluntary mov’t
VL Thalamic nucleusRed nucleusReticular Formation
Superior
NucleusInterpositus
VL thalamic nucleusRed nucleusReticular Formation
Superior
Fastigial Nucleus-balance andsends info
Vestibular Nuclei Superior(Uncinatefasciculus)Inferior(juxtarestiform)
Reticular Formation Superior(Uncinatefasciculus)
Inferior(juxtarestiform)
FlocculonodularCortex
Vestibular Nuclei Inferior(juxtarestiform)
From the Cerebral Cortexo
Important in the control of voluntary movement;initiation of movement1. Corticopontocerebellar pathway 2. Cerebro-olivocerebellar pathway 3. Cerebroreticulocerebellar pathway
From the Spinal Cord o Receives muscle joint information from muscle spindles,
tendon organs, and joint receptors of the upper andlower limbs
1. Anterior spinocerebellar tract2. Posterior spinocerebellar tract3. Cuneocerebellar tract
From the Vestibular Nerve (Vestibulocerebellar) o From the vestibular nerve to flocculonodular lobeo Receive information from the inner ear: motion(semicircular canal) and position (utricle and saccule)
A. From the Cerebral Cortex
Corticopontocerebellar Pathwayo Information from cerebral cortex particularly primary
motor and sensory areas and associative areas(different lobes of the cerebrum)
o Info descend through the corona radiata and internalcapsule
o Terminate on the pontine nuclei (corticopontine fibers)o The pontine nuclei give rise to the transverse fibers of
the pons
o Neurons project its axons from pontine nuclei tocontralateral cerebellar cortex which cross the midlineand enter the opposite cerebellar hemisphere as themiddle cerebellar peduncle.
VI. CEREBELLAR AFFERENT FIBERS
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Cerebro-olivocerebellar Pathwayo Descend through the corona radiata and internal
capsule to terminate bilaterally on the inferior olivarynuclei.
o The inferior olivary nuclei give rise to fibers that crossthe midline and enter the opposite cerebellarhemisphere through the inferior cerebellar peduncle.
o Information: motor area**Fibers that arise from inferior olivary nuclei terminate as
the climbing fibers in the cerebellar cortex, the rest will
terminate as mossy fibers
Cerebroreticulocerebellar Pathwayo Descend to terminate in the reticular formation on the
same side and on the opposite side in the pons andmedulla
o Cells in the reticular formation give rise to thereticulocerebellar fibers that enter the cerebellarhemisphere on the same side through the inferior andmiddle cerebellar peduncles.
o Information: motor areas
B. From the Spinal Cord
The spinal cord sends information to the cerebellum fromsomatosensory receptors (like muscles, tendons, joints)
Anterior Spinocerebellar Tracto Reach the posterior root ganglion
o Terminate by synapsing with the neurons in the nucleusdorsalis (Clarke's column)
o Nucleus dorsalis located at the base of the posteriorgray matter.
o Axons of these neurons go to anterolateral part of whitematter and ascend to reach brain stem and go throughsuperior cerebellar peduncle
o Fibers that cross over to the opposite side in the spinalcord cross back within the cerebellum
o Believed that the cerebellum receives information from
the skin and superficial fascia by this tracto Involve all segments of spinal cordo Convey muscle-joint information of upper and lower
limbs, skin and superficial fasciao Majority of fibers will cross
Posterior Spinocerebellar Tracto From the posterior root ganglion to the posterior gray
columno Project fibers in nucleus dorsalis (Clarke's column)o Posterolateral part of white matter cerebellar cortexo Enter cerebellum through inferior cerebellar peduncle
on same side then synapse in cerebellar cortexo Collateral branches that end in the deep cerebellar
nuclei are also given offo Convey muscle-joint information of trunk and lower
limbs
Cuneocerebellar Tracto Originate in the nucleus cuneatuso Enter the cerebellar hemisphere on the same side
through the inferior cerebellar peduncleo The fibers terminate as mossy fibers in the cerebellar
cortexo Collateral branches that end in the deep cerebellar
nuclei
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o Receives muscle joint information from the musclespindles, tendon organs, and joint receptors of theupper limb and upper part of the thorax
o Convey muscle-joint information particularly upperLimb and upper part, thorax
C. From the Vestibular Nerve
Vestibulocerebellaro receives information from the inner earo Project axons directly to cerebellumo Directly synapse with neurons in cerebral cortex through
inferior cerebellar peduncleo All the afferent fibers from the inner ear terminate as
mossy fibers in the flocculonodular lobe of the cerebellum.*All afferent fibers terminate in flocculonodular lobe*Other Afferent Fibers
Cerebellum receives small bundles of afferent fibers fromthe red nucleus and the tectum.
Receives information from the inner ear:o Motion - semicricular canalo Position relative to gravity - utricle and saccule.
Entire output of the cerebellar cortex is through the axons ofthe Purkinje cells .
Axons of the neurons that form the intracerebellar nucleiconstitute the efferent outflow from the cerebellum
Few Purkinje cell axons from the flocculonodular lobe by-pass intracerebellar nuclei pass through the juxtarestiformbody of the inferior cerebellar peduncle directly synapsewith the lateral vestibular nucleus
Efferent fibers from the cerebellum connect with the rednucleus, thalamus, vestibular complex, and reticularformation.
1. Globose-Emboliform-Rubral Pathway
Contained in the intracerebellar nuclei (via Globose andEmboliform or Nucleus interpositus) to the red nucleus/-i.
Axons travel through the superior cerebellar peduncle andcross the midline to the opposite side in the decussation ofthe superior cerebellar peduncles
Fibers end by synapsing with cells of the contralateral rednucleus, which give rise to axons of the rubrospinal tract
VII. CEREBELLAR EFFERENT FIBERS
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pathway crosses twice, once in the decussation of thesuperior cerebellar peduncle and again in the rubrospinaltract close to its origin.
influence motor activity on the same side of the body(ipsilateral motor activity)
2. Dentothalamic Pathway Axons travel through the superior cerebellar peduncle Cross the midline to the opposite side in the decussation of
the superior cerebellar peduncle Fibers end by synapsing with cells in the contralateral
ventrolateral nucleus of the thalamus Axons of the thalamic neurons ascend through the internal
capsule and corona radiata and terminate in the primarymotor area of the cerebral cortex.
Influence motor activity by acting on the motor neurons ofthe opposite cerebral cortex
Impulses from the motor cortex are transmitted to spinalsegmental levels through the corticospinal tract.
Deccusation of pyramido Remember that most of the fibers of the corticospinal tract
cross to the opposite side in the decussation of the pyramids orlater at the spinal segmental levels
Influences ipsilateral motor activityo Cerebellum indirectly influences on the same side
3. Fastigial Vestibular Pathway The axons of neurons in the fastigial nucleus travel
through the inferior cerebellar peduncle and end byprojecting on the neurons of the lateral vestibular nucleuson both sides
Some Purkinje cell axons project directly to the lateralvestibular nucleus.
The neurons of the lateral vestibular nucleus form thevestibulospinal tract.
The fastigial nucleus exerts a facilitatory influence mainly onthe ipsilateral extensor muscle tone.
4. Fastigial Reticular Pathway The axons travel through the inferior cerebellar peduncle
and end by synapsing with neurons of the reticularformation.
Axons of these neurons influence spinal segmental motoractivity through the reticulospinal tract. The efferent cerebellar Influences ipsilateral muscle tone
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1. Cortico-ponto-cerebello-dentato-thalamo-cortical Pathway Cerebral cortex -> pontine nuclei via corticopontine fibers Synapses at pontine nuclei –> Crosses then enter cerebellum
via the middle peduncle –> dentate nucleus –> Crosses again atsuperior cerebellar peduncle to thalamus then back to cortex
Double decussation –> at PONTINE LEVEL, SUPERIORCEREBELLAR PEDUNCLE (synapse)
Enter cerebellar cortex through the middle cerebellar peduncle Primary Motor Cortex -> descending motor pathways Thalamus : primary motor cortex
Dentatothalamic fibers project to the VL of the thalamus From motor cortex to loop influences descending motor PW’s Cortex > purkinje cell axons -> dentate nucleus
Synapses at pontine nuclei Crosses then enter cerebellum via themiddle peduncle Dentate nucleus Crosses again at superior
cerebellar peduncle to thalamus (thereby uncross prior reaching ththalamus- DENTATO-THALAMIC FIBERS) then back to cortex
Double decussation- [refer to the image above: at Pontinelevel, Superior Cerebellar Puduncle (synapse)
2. Vestibulo-archicerebellar Loop 1st pair to develop Balancing: Vestibular sytem Impluses from the vestibular nerve go to flocculonodular lobe
cortex (via vestibulocerebellar projection) and fastigial nucleus
Projections go to the vestibular and reticular nuclei inbrainstem
Exit via vestibulocerebellar peduncle Influences to spinal motor activity occur through the
vestibulospinal tracts
Vestibular nuclei Flocculonodular lobe cortex and fastigialnucleuso Projects to the VESTIBULAR AND RETICULAR nuclei i
brainstem (via juxtarestiform body at Inferior peduncle)o Influence spinal motor activity through the vestibulospinal
tracts
3. Brainstem-nuclei-cerebellar Loop Olivocerebral and Reticulocerebral enters thru the inferior
middle peduncle to the cortex (Lateral/Posterior) then go toPurkinje cells to the Nucleus Interpositus / Dentate Nucleithen to the Red / Reticulospinal then finally the spinal cord
Also follow Double Decussation Dentate Nucleus and Interposed Nucleus
Red Nucleus Reticular Nucleus
Rubrospinal Tract Reticulospinal Tract
Spinal Motor Activity
VIII. FEEDBACK LOOPS
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Lower brainstem nuclei and inferior olivary nucleus Reticulocerebellar and olivocerebellar tract Cerebellarcortex
Cerebellar cortex Purkinje cell axons Cerebellar deepnuclei
Origin:o cerebral cortexo muscles, tendons, and jointso vestibular nerve
Cerebellumo NO DIRECTneuronal connections with LMN’s (indirect) o coordinator of precise movements, bring about the
necessary adjustmentso influence activity of LMN’s Cerebellumo send back information -> inhibit agonist muscleso stimulate antagonist ms. -> limits voluntary movement
IX. CLINICAL CORRELATIONS
A. CEREBELLAR DISORDERS AND SYMPTOMS Hypotonia - decreased muscle tone Postural changes & alteration of gait Ataxia-gross lack of coordination or muscle movements
o Intention tremors – tremor during voluntarymovements
o Decomposition of movement- Pastpointing-Misjudging the location of an
object and pointing too far in the same
direction in which the object was displacedwhen presented monocularly in thedirection of action of a recently paralysedextraocular muscle.
- Heel to shin test Dysdiadochokinesia- inability to perform rapid
opposing/alternating movements Disturbances: Reflexes = Pendular knee reflexes Disturbances of Ocular Movement: Nystagmus-
involuntary eye movement
Dysarthria- difficulty speaking
B. COMMON DISEASES1. Acute Alcohol Poisoning
- Alcohol acting on GABA receptors of thecerebellar neurons
2. Alcohol Cerebellar Degeneration Severe chronic alcoholism with malnutrition Vermal degenerative changes
o Ataxia of gait but with normal speech and musclecoordination of upper extremities
3. Tumors Vermis Syndrome = Medulloblastoma (in Children)
Cerebellar Hemisphere Syndromeo Ataxia is very noticeable
C. ABNORMALITIES IN THE CEREBELLUM1. Neocerebellar Syndrome – Lesion of the lateral
hemispheric zone; asynergia, dysmetria, intention tremor- Asyngeria- Dysmetria- Past-pointing- Intention tumor- Dysdiadochokinesia- Rebound phenomenon- Decomposition of movement-scanning speech
o = Dysarthria
- Ataxia
2. Archicerebellar Syndrome – Damage to theflocculonodular lob and the related vermis; ataxia,uncoordinated gait, vomiting, and nystagmus
VIII. SUMMARY (CEREBELLAR CORTICAL CIRCUITRY)