Cerebellum Flashcards
What is unique about the cerebellum?
Receives sensory input but does not discriminate
Lesion rarely results in lasting muscle paralysis
Has component of motor/procedural learning
What does the cerebellum do?
Coordinate movements, maintain posture, motor learning/procedural memory
What indirect motor tracts does the cerebellum influence?
Tectospinal, vestibulospinal, reticulospinal, rubrospinal
What are the deep cerebellar nuclei?
Dentate
Emboliform
Globos
Fastigial
What are the layers of gray matter and the cell types found within?
Molecular layer - basket and stellate cells
Purkinje layer - purkinje cells
Granular layer - granule and golgi cells
What do purkinje cells do?
Efferents - major output from cerebellar cortex to different nuclei. Inhibit deep cerebellar nuclei and vestibular nuclei via GABA
What do granule cells do?
Only excitatory neurons (glutamate), found in granule layer
What do golgi cells do?
Inhibitory neurons (GABA), found in granule layer
What do stellate cells do?
Synapse only with purkinje cells and inhibit them, found in molecular layer
What do basket cells do?
Synapse with purkinje cells and inhibit them (GABA), found in molecular layer
What are mossy fibers?
Come from SC, RF, vestibular system, and pontine nuclei to excite granule cells and deep cerebellar nuclei. Convey somatosensory, arousal, equilibrium, and cerebral cortex motor info
What are climbing fibers?
Come from inferior olive (in medulla) to excite purkinje cells and deep cerebellar nuclei. Convey movement errors to cerebellum
What are the functional divisions of the cerebellum?
Vestibulocerebellum, spinocerebellum, pontocerebellum/cerebrocerebellum
What is the vestibulocerebellum?
Flocculonodular lobe + nodulus, receives info from vestibular receptors and visual areas, sends output to vestibular nuclei via purkinje cells that bypass deep cerebellar nuclei. Influences eye movements and balance/equilibrium
What is the spinocerebellum?
Vermis + paravermal region. Receives somatosensory info from spinal interneurons and sensorimotor cortex, output to medial UMNs and lateral UMNs for gait
What is the pontocerebellum?
Lateral hemispheres of cerebellum, also known as cerebrocerebellum. Input from cerebrum (premotor, sensorimotor) via pontine nuclei. Coordinates voluntary movements (planning and timing)
What are the globos nuclei and emboliform nuclei called?
Interposed
What is the big picture of input to the cerebellum?
Afferents –> cerebral peduncles –> three functional divisions of cerebellum –> purkinje cells (efferents) –> four deep cerebellar nuclei –> second set of efferents –> targets
What afferent fibers go to the cerebellum from the vestibular system?
Vestibular nuclei and CN VIII. Mossy fibers via inferior cerebellar peduncle
What afferent fibers go to the cerebellum from the SC?
Posterior spinocerebellar tract (legs) and cuneocerebellar tract (arms)
Also anterior spinocerebellar tract (legs) less important. Mossy fibers via inferior cerebellar peduncle
What afferent fibers go to the cerebellum from the cerebral cortex?
Cortico-pontocerebellar and cortico-reticulocerebellar (mossy fibers via middle cerebellar peduncle)
Cortico-olivocerebellar (climbing fibers via middle cerebellar peduncle)
What is the pathway of the posterior spinocerebellar tract?
Primary afferent cell body in DRG, travels up in gracile fasiculus until synapsing in Clark’s nucleus (C8-L2) if lower down. Secondary neuron in Clark’s nucleus travels in posterior spinal tract until reaching inferior cerebellar peduncle (restiform body) to get to cerebellum
What is the pathway of the cuneocerebellar tract?
Primary afferent cell body in DRG, travels up in cuneate fasiculus to lower medulla to synapse on accessory cuneate nucleus. Secondary neuron cell body in accessory cuneate nucleus, travels up to inferior cerebellar peduncle (restiform body)
Where do afferent fibers coming from vestibular system enter the cerebellum?
Juxtarestiform body in inferior cerebellar peduncle
What makes up inferior cerebellar peduncle?
Juxtarestiform body and restiform body
What fibers do the superior cerebellar peduncles carry?
Efferents from globose, emboliform, and dentate nuclei. Afferents from anterior spinocerebellar tract (tract that crosses twice)
What fibers do the middle cerebellar peduncles carry?
Afferents from pontine nuclei relayed to cortex
What fibers do the inferior cerebellar peduncles carry?
Afferents from spinal cord
Where does the fastigial nucleus communicate with?
Vestibular nucleus and reticular formation
Explain how the fastigial nucleus communicates with the vestibular nuclei
Fastigial nucleus sends fibers to vestibular nucleus which sends fibers to vestibulospinal tract
Explain how the fastigial nucleus communicates with the reticular formation
Fastigial nucleus sends fibers to pontine reticular formation and medullary reticular formation which sends fibers down reticulospinal tracts to affect posture
Where does the dentate nucleus communicate with?
Red nucleus and thalamus (VL)
Explain how the dentate nucleus communicates with the thalamus
Leaves via superior cerebellar peduncle. Goes to VL of thalamus which sends fibers to motor cortex. Can also go to red nucleus in midbrain which affects rubrospinal tract for flexion of upper limbs
Where do interposed nuclei communicate with?
Red nucleus and thalamus (VL)
What system helps in correction of motor errors?
Anything that runs from cortex to olive to cerebellum
Unilateral lesion of cerebellum results in deficits where?
Ipsilateral side motor issues and ataxia w/ wide-base gait and pt falhe ling to side of lesion when walking
What does a lesion to the vestibulocerebellum do?
Eye movements, balance, and equilibirum problems. -Nystagmus, truncal ataxia (difficulty maintaining sitting/standing), truncal instability (titubation - shaking back and forth), and problems w/ tandem walking (midline ataxia)
What does a lesion of the spinocerebellum do?
Wide-based gait and difficulty tandem walking (midlilne ataxia)
What does a lesion of the cerebrocerebellum do?
Dysarthria, ataxic gait (staggering), decomposition of movements/speech, dysdiadochokinesia (inability to rapidly alternate movements), dysmetria (inability to accurately move intended distance), and action tremor (shaking of limb during voluntary movement)
What is midline ataxia vs appendicular ataxia?
Midline - damage to vestibulocerebellar and spinocerebellar areas. Truncal instability and gait ataxia
Appendicular - damage to cerebrocerebellum. Problems with limbs, ataxia of speech, decomposition of movement, dysmetria, dysdiadochokinesia
What is cerebellar ataxia?
Damage to cerebellum. Positive romberg test (cannot stand with feet together with eyes open or shut). Normal vibratory sense, proprioception, and ankle reflexes
What is sensory ataxia?
Damage to dorsal columns. Positive romberg test (but can stand with feet together with eyes open). Abnormal vibratory sense, proprioception, and ankl reflexes
