Cerebellum Flashcards
Inability to maintain proper balance resulting from cerebellar lesion
Results mainly from disruption of input from the vestibular system
disequilibrium
Decreased muscle tone and difficulty in maintaining posture resulting from cerebellar lesion
Results from disruption of spinocerebellar inputs
hypotonia
Lack of coordination of muscles that usually work together resulting from cerebellar lesion
Results from damage to the pathways from higher levels (cortico-ponto-cerebellar) or from lower levels (spinocerebellar)
asynergia
lack of coordination of voluntary movements resulting from cerebellar lesion
ataxia
Tremor most apparent during a planned movement just before the patient reaches the target resulting from cerebellar lesion
intention tremor
Patient tends to overshoot or undershoot reaching for a target resulting from cerebellar lesion
dysmetria
Mainly contains fibers entering the cerebellum from spinal cord and brainstem
Contains outputs to the medulla oblongata, vestibular nuclei and reticular formation
Attaches cerebellum to the medulla oblongata
inferior cerebellar peduncle
Only contains fibers entering the cerebellum from pons
Attaches the cerebellum to the pons
middle cerebellar peduncle
Mainly contains cerebellar outputs going to the red nucleus and VA/VL thalamus
Exception – input from spinal cord (ventral spinocerebellar tract)
Attaches cerebellum to the midbrain
superior cerebellar peduncle
cerebellar input
Originates from nucleus Dorsalis of Clark (C8-L2)
Runs on the ipsilateral side of the spinal cord and brainstem
Enters the cerebellum by via the inferior cerebellar peduncle
Axons synapse mainly in the anterior lobe of the cerebellum
Conveys information regarding muscle tone for the lower extremity
dorsal spinocerebellar tract
cerebellar input
Originates from posterior horn neurons in the spinal cord at all cord levels
Axons cross in anterior commissure of the spinal cord
Enters cerebellum in the superior cerebellar peduncle
Axons synapse mainly in the anterior lobe of the cerebellum
Conveys information about whole muscle movement
ventral spinocerebellar tract
cerebellar input
First order neuron (DRG cells) axons ascend in the dorsal funiculus to synapse in the lateral cuneate nucleus of the medulla oblongata (lateral to the nucleus cuneatus)
Axons of neurons in the lateral cuneate nucleus form the cuneocerebellar tract which enters the cerebellum in the inferior cerebellar peduncle and projects to the anterior lobe
Conveys information regarding muscle tone for the upper extremity
cuneocerebellar tract
cerebellar input
Axons cross in the medulla oblongata and enter the cerebellum in the inferior cerebellar peduncle
Axons project to the entire cerebellar cortex
inferior olivary nucleus
cerebellar input
Axons enter the cerebellum in the inferior cerebellar peduncle
Axons project mainly to the anterior lobe
reticular formation
cerebellar input
Axons enter the cerebellum in the inferior cerebellar peduncle
Axons project mainly to the flocculonodular lobe
vestibular nuclei axons and vestibular ganglion cell axons
cerebellar input
Axons from cerebral cortex synapse in the pontine grey nuclei
Axons of the pontine grey nuclei form pontocerebellar axons which cross in the pons to enter the cerebellum in the middle cerebellar peduncle
Motor areas of cerebral cortex project to cerebellum via pons
cerebral cortex does not connect directly to cerebellum but relays through pons
superficial layer of cerebellar cortex
located under the pia mater, contains mainly large bundles of unmyelinated axons packed together (parallel fibers) and dendrites of Purkinje cells
molecular layer
intermediate layer of cerebellar cortex
single layer of Purkinje cell bodies
Axons of Purkinje cells leave the cerebellar cortex and synapse with neurons in deep cerebellar nuclei
Purkinje cells are all inhibitory and are the only neurons of cerebellar cortex whose axons leave the cerebellar cortex
All others neurons in cerebellar cortex are interneurons
Purkinje cell layer
deep layer of cerebellar cortex
granule cells whose axons form the parallel fibers running in the molecular layer and synapsing on Purkinje cell dendrites, parallel fibers are excitatory
granular layer
originate from neurons in the spinal cord, reticular formation, vestibular nuclei, potine grey, and vestibular ganglion cells
Synapse mainly with granule cells
Enter the cerebellar cortex and send collateral axon branches to the deep cerebellar nuclei neurons where they synapse
excitatory fibers
mossy fibers
originate from neurons in the inferior olive and synapse mainly on dendrites of the Purkinje cells in the molecular layer
Enter the cerebellar cortex and send collateral axon branches to synapse on neurons in the deep cerebellar nuclei
excitatory fibers
climbing fibers
deep cerebellar nucleus
lies close to midline
receives input from Purkinje cells in the vermis, vestibular nuclei, and vestibular ganglion cells
outputs mainly go to vestibular nuclei and reticular formation
concerned with regulating extensor muscle tone and adjusting posture
fastigial nucleus
deep cerebellar nucleus
Several small groups of neurons found lateral to the fastigial nucleus
Receives input from Purkinje cells in the intermediate zone
Output goes to the red nucleus and VA/VL thalamus
Concerned with regulating flexor muscle tone and limb movements
globose nucleus and emboliform nucleus (interposed nucleus)
Largest and most laterally places deep cerebellar nuclei
Receives input from Purkinje cells in the lateral cerebellar hemispheres
Output foes to red nucleus and VA/VL thalamus
Concerned with coordinating somatic motor activity by influencing motor regions of cerebral cortex
Coordinates finger movements and skilled movements
dentate nucleus
