Hirsch - Cerebellum Flashcards
function of cerebellum
compare motor plans with physical execution
make adjustments to keep movements coordinated, fluid, and on target
also involved in motor learning
cerebellar disorder
- ataxia
reeling, wide based gait
cerebellar disorder
- decomposition of movement (general)
inability to correctly sequence fine, coordinated acts
cerebellar disorder 2.1. dysarthria
inability to articulate words correctly with slurring and inappropriate phrasing
cerebellar disorder 2.2. dysdiadochokinesia
inability to perform rapid alternating movements
cerebellar disorder 2.3. dysmetria
inability to control range of movement (hypo or hypermetria)
cerebellar disorder 2.4. hypotonia
decreased muscle tone
cerebellar disorders 2.5. nystagmus
involuntary, rapid oscillation of the eyeballs in a horizontal, vertical or rotary direction with the fast component maximal toward the side of the cerebellar lesion
cerebellar disorders 2.6. tremor
rhythmic, alternating, oscillatory movement of a limb as it approaches a target (intention tremor) or of proximal musculature when fixed posture or weight bearing is attempted (postural tremor)
arbor vitae
whitematter of cerebellum
functional divisions of cerebellar cortex
cerebrocerebellum (neocerebellum)
spinocerebellum (paleocerebellum)
vestibulocerebellum
cerebrocerebellum
lateral
phylogenetically new
receive input from contralateral cerebral cortex
regulate complex sequence of movement including speech
spinocerebellum
paramedian and median (vermis zone)
phylogenetically older than neocerebellum
receive input from spinal cord
somatotopic organization
* paramedian: regulate distal muscles
* median: regulate proximal muscle and some eye movements
vestibulocerebellum
caudal and inferior lobes
phylogenetically ancient
receives input from vestibular nuclei (in brainstem)
regulate posture and balance including eye movements
deep cerebellar nuclei
dentate
interposed
fastigial
dentate nucleus
input from cerebrocerebellar zone
projects to:
- contralateral premotor cortex
- association cortices of frontal lobe involved in planning movement
Interposed nucleous
globose nucleus + emboliform nucleus
input from spinocerebellar zone
projects to:
contralateral motor cortex (aid executing movement)
Fastigial nucleus
input from spinocerebellar zone
projects to:
upper motor neurons (in ipsilateral brainstem)
to aid executing movement
vestibulocerebellum
project to vestibular nuclei
NOT to cerebellar nuclei
cerebellar peduncles
*afferent connection arrives
*efferent connection exits
fiber bundles carrying inputs and outputs
- superior (brachium conjuntivum)
- middle(info to cerebellum)
- Inferior (restiform body
superior peduncles - cerebellar
efferent pathway exiting from deep cerebellar nuclei
middle peduncles
afferent pathway carrying information from the cortex via the pons
inferior peduncle
mixed;
afferent come from brainstem and spinal cord
efferent exit from vestibulocerebellum
know picture in (7/16) for structures associated with cerebellum
medial premotor cortex and primary motor cortex
VA/VL complex of thalamus
cerebellar cortex
deep cerebellar nuclei
pontine nuclei
vestibular nuclei
inferior olive
external cuneate nucleus
dorsal nucleus of Clarke
Inputs to cerebellum
- from cerebral (frontal/parietal) cortex:
project to pontine nuclei (ipsilateral)
controls contralateral side of the body
- cerebellar hemisphere:
receive ascending input from ipsilateral side of body
control movements on the same side of the body
** pathway from cerebral cortex to cerebellum cross at middle cerebellar peduncle
Ascending outputs of the cerebellum
cerebrocerebellum -> premotor cortex via dentate (motor planning);
part of it spreads to red nucleus parvocellular
spinocerebellum -> motor cortex via interposed nuclei (motor execution)
descending outputs of the cerebellum
spinocerebellum -> brainstem via fastigial nucleus (motor execution)
vestibullocerebellum -> project directly to vestinular nuclei (motor adjustment, balance)
Cytoarchitecture of the cerebellum
three layers of cerebellar cortex from out to in
- molecular layer (ML) - dendrites of purkinje cells and axons of granule cells (parallel fibers)
- Purkinje cell layer (PL) - purkinje cells and basket cells
- granule cell layer (GL) - granule cells have “claws”
cerebellar circuits
climbing fibers
mossy fibers
climbing fibers - comes from inferior olive
mossy fiber - comes from pontine nuclei
climbing fiber and purkinje cell
purkinje cell receive input from a single clibing fiber (from inferior olive) (ONE)
fires “complex spike” in response to input from a clibing fiber
inferior olive
makes single climbing fiber to purkinje cells
receives input from cerebral cortex, spinal cord, and “red nucleus”
mossy fiber and purkinje cell
come from pontine nuclei
synapse with granule cells
purkinje cell receives hundreds of thousands of inputs from parallel fibers (MANY)
purkinje cells fire “simple” spikes in response to input from parallel fibers
pontine nuclei
make mossy fibers to granulle cell (parallel fibers)
relay input from cerebral cortex, spinal cord and “vestibular nuclei”
motor learning: cerebellum can learn to compensate changes in the status quo
ex. normal vestibulo-ocular reflex (VOR) vs. VOR out of register using minifying glasses
—> VOR gain reset by moving eyes in smaller distance to compensate
movement adjusts to the vision
cerebellar loops
- direct loop (deep excitatory)
- cortical inhibitory loop
- climbing fiber loop
direct loop; deep excitatory
from mossy fibers
(afferent information)
to deep cerebellar nuclei
“motor system - a reflex pathway”
cortical inhibitory loop
from mossy fibers
via parallel fibers
to granule cells
to purkinje cells
to ddep cerebellar nuclei and motor system
“to fine-tune reflexes”
climbing fiber loop
detect errors
correct them over longterm
“motor learning loop”
motor learning
climbing fiber loop & complex spike
important
climbing fibers derive from ______
mossy fibers come from ______
climbing fibers derive from inferior olive
mossy fiber come from pontine nuclei
know how to draw (16/16)
- planning and programming
(sensory association cortex, basal ganglia, lateral hemisphere of cerebrocerebellum ===>premotor cortical area)
- movement
( ==> motor cortex, vermis and intermmediate hemisphere of spinocerebellum)
- feedback signals
(vermis and intermediate hemisphere of spinocerebellum)
