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Cerebellar hemispheres
Lateral hemispheres
Intermediate hemispheres
Superior cerebellar peduncle
- connects to rostral pons
- contains mostly efferent fibers
Middle cerebellar peduncle
- connects to pons
- contains mostly afferent fibers from cerebral cortex
Inferior cerebellar peduncles
- connects to cuadal pons/rostral medulla
- contains mostly afferent fibers from BS and SC
- contains efferent to vestibular nuclei and RF in brainstem
Cerebellum
- detects movement that deviates from the intended cortical command.
- smoothly coordinates ongoing movements
- contributes to motor planning
- receives massive amounts of sensory input about actual movement from the spinal cord cerebellar tracts
- integrates this sensory information and adjusts movement as necessary
Three major functions of the cerebellum:
- Synergy of movement: groups movements for the performance of selective responses
- Maintenance of Upright Posture: Body position in space
- Maintenance of Tone: maintaining tone during muscle contraction
Also participates in speech articulation, respiratory movements, motor learning and possibly higher-order cognitive processes
Three functional regions of the cerebellum
Lateral hemispheres
Intermediate hemispheres
Vermis and flocculonodular lobe
Lateral hemisphere of cerebellum function
- motor planning for extremities
- lateral corticospinal tract
Intermediate hemisphere of the cerebellum function
- Function: distal limb coordination
- lateral corticospinal tract, rubrospinal tracts
Vermis and flocculonodular lobe of teh cerebellum function
- proximal limb and trunk coordination : anterior corticospinal tract, reticulospinal tract, vestibulospinal
- balance and vestibuloocular reflexes: medial longitudinal fasciculus
Input to cerebellar cortex:
- mossy fibers (excitatory)
- climbing fibers (excitatory)
—both synapse directly or indirectly on Purkinje cells. Inputs to ther cerebllar cortex also have collateral fibers that synapse on deep cerebellar nuclei
Output from cerebellar cortex:
Purkinje fibers (inhibitory)
-project to the deep cerebellar nuclei and/ or vestibular nuclei (excitatory)
Deep cerebellar nuclei serve as…
Serve as an on/off center for cerebellar output
What are the Deep cerebellar nuclei?
-Lateral to medial “Don’t Eat Greasy Foodds”
- Dentate: input from lateral hemisphere
- Emboliform: input from intermediate hemisphere
- Globase: input from intermediate hemisphere
- Fastigial: input from vermis
Vestibular nuclei
- Function in some ways like deep cerebellar nuclei
- input from inferior vermis and flocculonodular lobe
Main cerebellar output pathways
Lateral hemispheres- Dentate
Intermediate hemispheres- interposed
Vermis- fastigial
Inferior vermis and flocculonodular lobe - vestibular
Why do cerebellar lesions cause ipsilaterall deficits in coordination?
- Pathways from the cerebellum that influence the lateral motor systems and periphery are double crossed
- lesions of the vermis don’t cause unilateral deficits because medial moor systems influence bilateral proximal trunk musculature
Who sends input to the cerebellum?
- input to the cerebellum id from virtually all areas of the cerebral cortex, many sensory modalities, brainstem nuclei, and the SC
- corticopontine fibers
- input also from vestibular nuclei, RF nuclei, and inferior olivary nuclei
Corticopontine fibers
- fibers traveling from the cerebral cortex to the cerebellum
- synapse in pons, and then are called pontocerebellar fibers
Spinocerebellar pathways
- unconscious proprioception of limb movements : dorsal spinocerebellar tract (LE), cuneocerebellar tract (UE)
- unconscious information regarding activity of spinal interneurons, as well as spinal reflex circuits: ventral spinocerebellar tract (LE), rostral spinocerebellar (UE)
- each cerebellar hemisphere receives information from the ipsi limbs. Inputs either dont cross or are double crossed
Ataxia side of lesion
- ipsi to the side of the lesion
- b/c of reciprocal connection between cerebellum, brainstem, an other regions, ataxia may be seen with lesions in these other location as well
- uncoordinated movement. Disordered contractions of agonist and antagonist muscles and lack or normal coordination b/w movements at different joints. Movements have irregular, wavering course that consists of continuous overshooting and over correcting
Midline lesions of the cerebellum
-unsteady gait and eye movement abnormalities
Lesions lateral to the vermis of cerebellum
-limb ataxia
-
Three classic signs of cerebellar damage
“ANT”
Ataxia, nystagmus, and (intention) tremor (with movement)
Also could have: dysrhythmia, dysdiadochokinesia, dysmetria
- Vertigo, N/V, unsteadiness, slurred speech, HA