movment disorders Cerebellum Flashcards
synergy of movement
elemental muscular contractions are coordinated to create purposeful movement
posture
whereby the body is oriented appropriately relative to the vector of gravity
muscular tone
muscles exhibit appropriate basal levels of contraction to determine posture
comparator actions of cerebellum
copies of motor instructions get to cerebellum and it compares gets sensory feedback and then compares it with the original motor instructions. if the outcomes are mismatched its ends corrective signals to the motor centers
basic rule of cerebllar function
- cerebellum innervates the ipsilateral body indirectly
acute cerebellar damage uields
pronounced ipsilateral motor deficits.
substantail functional recovery often occurs with
long standing but non progressive crebellar damage
embryological origin of cerebellum
protuberance of the mesencephalon
anterior lobe is superior to
the primary fissure
the cerebellar hemisphere indirectly regulates
the ipsilateral body
trunk is functionally regulated by
more medial cerebellar structures
limbs are functionally regulated by
more laterally cerebellar structures.
vestibulo cerebellum
cooresponds with the flocculonodular lobe, most afferents arise form the vestibular apparatus regulating balance and eyemovements
spinocerebellum
overlaps primarily with anterior node. provides region with sensory feedback regarding consequences of motor activity, assisting with regulation of gross truncal and limb movements
cerebro cerebellum
overlaps with psoterior lobe. integrates instructions with sensory feedback to smooth movements requiring precision and location and timing.
cerebellar efferents and afferents form
cerebellar peduncles
middle peducnle carries
info from pons to cerebellum
superior and inferior peduncles carry
bidirectional traffic with theinferior peduncle being the greater conductor of afferents.
Superior peduncle transmit to
pons and midbrain(except vestibular nuclei
inferior cerebellar relay
info from spinal levels into the cerebellum
supeiror peduncle also contributes to
communications with olive, CN VIII , vestibular nuclei.
suprspinal inputs
cerebro-ponto-cerebellar, rubro-olivo, reticulo, vestibulo, tecto-ponto, trigeminal, monoaminergic
copies of corticospinal an corticobulbar signals terminate in
the ipsilateral deep pontine nuclei
pontocerebellar fibers cross the mid line to
enter the cerebellar hemisphere opposite to the cortical site of origin via the middle cerebellar peduncle
rubro efferents that don’t cross as part of the rubrospinal tract may descend to
the rsotral medulla to synapse in the inferior olivary nucleus
olivo-cerebellar fibers cross the midline of the medulla to
enter the cerebellum
reticular formation normally influences
muscle tone and informs the cerebellum
vestibular afferents my pass directly
from CN VIII into the ipslateral flocculonodular lobe
Vestibular nuclei less directly relay
additional signals arising from cranial nerve VII
tectum orients
the head and eyes towards potential threats based on auditory, visual and somatosensory info
tectal motor signals reach
the cerebellum
trigeminal nuclei provides
inputs to the cerebellum
pontine and medullary nuclie project to
the cerebellum providing monaminergic modulation
Spinocerebellar inputs
dorsal spinocerebellar, ventral spinocerebellar, cuneocerebelllar.
ventral spinocerebellar system is
an array of receptors that contribute to analysis of whole limb movement communicating with spinal gray matter
spinal neruons sends acons acroos the cord to
ascend to the superior cerebellar penduncle to enter the cerebellum
many of the spinal neurons of the ventral spinocerebellar system cross a second time
within the cerebellum. (this is functionally similar to the pathway that doesn’t cross.
neuromuscular spindles and golgi tendon organs transmit signals related to
specific msucles into the spinal dorsal horn
the dorsal spinocerebellar pathway scends
ipsilaterally to enter the cerebellum via the inferior cerebellar peduncle
proprioceptors for the uppper limbs contribute to
the ipslateral fasciculus cuneatus which terminats int he medullary nucleus cuneatus
external aruate fibers enter the cerebellum throguh
the ipsilateral inferior cerebellar peduncle as the cuneo cerebellar pathwya.
beneath meninges is
the cerebellar cortex
beneath the cerebeallar cortex is
the subcortical white matter
embedded within the subcortical white matter are
clusters of cell bodies which are analogous to the basal nuclei of the cerebrum
near the deep cerebellar nuclei is the
ventricular system(fourth ventricle, analogous with the lateral ventricles.
two basic types of fibers enter the cerebellum largely terminating in the
cortex but also the dep cerebellar nuclei
climbing fibers arise from the
inferior olivary nuclei
mossy fibers constistue
the remainder of the cerebellar afferents.
cerebellar cortex is organized as
foila and is laminated
closest to the white matter lie
the cortical granule cells which form the granule layer and receive inputs from mossy fibers
vestibulo cerebellum distrubances affect
equilibrium related motor functions: nystagmus, tilted head, titubation
spino cerebullum disturbances affect
posture and movements of limbs: ataxias, gait ataxia accompanied by lurching to the side of the lesion
cerebro cerebellum disturbances affect
accuracy and timing of movement: ataxia, decomposition of movement, dysarthria(slurred monotous speech), dyssynergia(no rapid alternating movements, dysmetria(past-pointing, hypotonia, intention tremor, rebound phenomenon
midline astrocytomas
occur most commonly in children - broad based stance with impaired tandem walking -nystagmus - truncal ataxia - headache -hydrocephalus -elevated IP -nausea and vomiting
granule cell axons ascend to
the superficial cortical layer, then bifurcate, wiht one process traveling medial and the other laterally
golgi cells provide
inhibitory feedback to granule cells
dendrites of purkinje cells occupy
the superficial layer of the cortex
paralllel fibers excite the
dendrites of the purkinje cells and local inhibitory interneurons
climbing fibers ascend to
synpase directly on the dendrites of the purkingje cells, spreading excitation in the rostrocaudal palne
between the molecular and granule layers is
the purkinje layer occupied by large purkinje somata
one excite purkinje cells transmit signals
down their axons which exit the cortical gray matter
purkinje cells commonly release
GABA onto deep cerebellar nuclear cells.
deep nuclear cells emit
cerebellar efferent axons
fastigial efferents reach medail vestibular nuclei
to influence reflexive movements of the eyes, head and neck
fastigial efferents reach lateral vestibular nuclei to
ipsilaterally influence movements of the limbs and trunk.
fastigial efferents reach pontine and medullary reticular formations
influence a broad array fo muscles.
efferents of the interpsoed nucleus communicates with
the contralateral red nucleus to infuence the output of the rubrospinal system.
the dentate nucleus receives input from
the lateral cerebellar hemispheres and communicates with the contralateral ventrolateral nucleus of the thalamus to influence the cortical motor systems.
Cerebellar stroke
usualy the verteberal artery system -unilateral occlusive disease -Dysarthria -Dyssynergia(ipsilateral) -Dysmetria -Dysdiadokinesia -intention tremor(ipsilateral) -limb ataxia(ipsilateral) -rebound phenomenon(ipsilateral -truncal ataxia - brainstem signs not common because cerebellar arteries supply it
Vitamin B1 deficiency linked to
degeneration of the anterior vermis and adjacent parts of the remaining anterior cerebellar lobe - cortical purkinje degeneration -reactive gliosis -dysmetria of legs and lurching gait -truncal ataxia and intention tremor -recovery can follow
Louis-Bar syndrome
-degeneration of cerebellar purkinje cells and compromised immune function -delayed development in walking, talking facial and ocular movement - sensitivity to ionizing radiation -increased vulnerability to cancer -skin and eyes express dilated blood vessels
cerebellar cognitive affective syndrome
lesions of posterior lobe -failures of cognitive and emotional systems -emotional blunting and depression, disinhibtion, psychotic features. -executive, viual-spatial, and linguistic deterioration - dysmetria of thought.
Four motor centers that contribute to cerebellum input
primary motor cortex, reticulospinal tract, vestibulospinal stract, rubrospinal tract
