Cerebellum Flashcards
cerebellum
-functions
smoothing and sequencing of movements
supporting postural adjustments and eye movements
establishing and modifying motor programs
interacts with ascending sensory pathways, vision, vestibular function, and cortical plans for movement
provides comparison of internal and external feedback
modifies central motor programs
provides a center for motor learning or memory
does the cerebellum run under excitatory or inhibitory control?
inhibitory
if you have increased intracranial pressure in the posterior fossa, what portion of the cerebellum may herniate through the foramen magnum and affect the medulla
cerebellar tonsils
what are the deep cerebellar nuclei
-location
fastigial nuclei dentate nuclei interposed nuclei -globose nucleus -emboliform nucleus located in the white matter of the cerebellum, deep to the cortical circuitry
what cells inhibit the deep cerebellar nuclei
purkinje cells
cerebellar lobes
anterior
posterior
flocculonodular
if cerebellar tonsils pinch the medulla, what would the symptoms be?
pressure-like headaches at the back of the skull that worsen with physical strain or coughing; often with neck pain hoarseness or swallowing problems sleep apnea weakness or numbness in an extremity balance problems
deep cerebellar nuclei influence lower motor neuron activity through…
indirect connections to descending motor systems
- vestibulospinal
- reticulospinal
- rubrospinal
- corticospinal
layers of the cerebellar cortex
outer layer
middle layer
granular layer
cerebellar cortex: outer layer
-composition
axons and dendrites molecular layer (no cell bodies)
cerebellar cortex: middle layer
- composition
- function
- receives…
Purkinje cells
-form the output of the cerebellar cortex
influence the activity of the deep cerebellar nuclei by inhibiting them
recieves one major afferent system
cerebellar cortex: granular layer
- receives majority of input from…
- -how does it receive it?
- axons of this layer form majority of axons in _____ and synapse on _____
receives the majority of input from afferent systems
-via mossy fibers
form majority of axons in molecular layer and synapse on dendrites of the purkinje cells
dentatorubrothalamic pathway
- function
- involved in…
- how does it work
primary efferent pathway
involved with motor planning
-before voluntary movements, alterations in dentate neural activity precede changes in cortex activity –> coordination, planning, and timing of movements
what are the spinocerebellar afferent pathways
-where are the pathways found?
high fidelity pathways (inferior cerebellar peduncle)
-posterior spinocerebellar
-cuneocerebellar
internal feedback tracts (superior cerebellar peduncle)
-anterior/ventral spinocerebellar
-rostrospinocerebellar
ventral and rostral spinocerebellar pathways
- carry what information
- what is the pathway of this information?
- tracts cross through
carry integrated information of both sensory and motor activity from the ipsilateral cord
cross contralateral at a spinal cord segment and then recross through the superior cerebellar peduncle
ventral and rostral spinocerebellar pathways
-function
provide internal feedback by monitoring the activity of spinal interneurons and of descending motor signals from the cerebral cortex and brainstem
posterior spinocerebellar and cuneocerebellar pathways
- function
- tracts run through…
relay high-fidelity ipsilateral proprioceptive information from the lower and upper extremities
tracts run through inferior cerebellar peduncle
how does diabetes affect the spinocerebellar afferent pathways
dysfunction of proprioceptive neurons can cause increased sway during stance, along with ataxia
middle cerebellar peduncle
- what fibers?
- fibers are carrying…
- these fibers are relayed through…
- this relay receives _____ from _____
pontocerebellar fibers that are carrying information relayed through pontine nuclei in the ventral pons
this relay receives cortical information from all parts of the cortex
inferior cerebellar peduncle
-contains what pathways
dorsal spinocerebellar cuneocerebellar olivocerebellar trigeminocerebellar vestibulocerebellar fastigiovestibular
inferior cerebellar peduncle: dorsal spinocerebellar and cuneocerebellar pathways
-function
carry specific joint and muscle information encoded by GTOs, muscle spindles, and joint capsule receptors
dorsal: LE
cuneo: UE
inferior cerebellar peduncle: olivocerebellar pathway
- arises from…
- gives rise to…
arises from contralateral inferior olivary complex
gives rise to climbing fibers
inferior cerebellar peduncle: trigeminocerebellar pathways
-function
carry similar somatosensory information from the face, jaw, and extraocular eye muscles
inferior cerebellar peduncle: vestibulocerebellar pathway
-function
carries axons from the vestibular nuclei as well as direct fibers from vestibular apparatus
inferior cerebellar peduncle: fastigiovestibular pathway
-function
carries an efferent pathway from the fastigial and interposed nuclei to the vestibular nuclei and reticular nuclei
there are some purkinje cell axons that bypass the deep cerebellar nuclei and project directly to the vestibular nuclei
in normal circumstances, function of the mossy fibers
convey somatosensory, equilibrium, and cerebral cortex information –> Granule cell –> Purkinje cell
when movement errors occur, what happens?
inferior olivary complex sends a signal using climbing fibers
these fibers send a strong signal to Purkinje cells, which adjust the firing pattern and therefore output of the cerebellum, so that motor learning takes place
climbing fibers are thought to…
send a “teaching” signal” to the cerebellum, for motor learning
functional divisions of the cerebellum
spinocerebellum
vestibulocerebellum
cerebrocerebellum
vestibulocerebellum
- composition
- how does it work
- function
made up of flocculonodular lobe
how
-receives input from the vestibular nuclei and apparatus
-sends received information back to influence vestibular nuclei function and reticulospinal pathways
function
-controls equilibirum, eye movements, trunk and postural tone
spinocerebellum
- contains
- receives info from…
contains -majority of the vermis and paravermal zones -much of the anterior lobs receives information from -spinal cord (muscle spindle, GTO, touch information) -auditory -visual -vestibular -trigeminal -motor cortex
spinocerebellum
- output is to…
- function
output is to medial and lateral descending pathways (reticulospinal and vestibulospinal) through both the interposed and fastigial nuclei
involved in controlling limb movements and muscle tone for error correction resulting in coordinated movements
functions more at proximal limb joints
cerebrocerebellum
- composition
- receives info from…
composition
-lateral parts of the cerebellar hemispheres, primarily the posterior lobe
receives information from widespread areas of the cortex via pontine nuclei
cerebrocerebellum
- primary output
- functions
primary output
-motor and premotor cortex through the dentatorubrothalamic pathway
functions
-planning and coordination of voluntary movements
-“memory” of those movements
unilateral cerebellar lesions
- affects which side of body?
- -why?
affects ipsilateral body
-efferents either go to ipsilateral medial descending tracts
OR
-project to contralateral cortex and red nucleus, who descending tracts cross back over
S/S of vermal and flocculonodular lobe cerebellar lesion
trunk ataxia
S/S of paravermal lesion
gait and limb ataxia
S/S of lateral cerebellar lesion
hand ataxia
S/S of vestibulocerebellum lesion
nystagmus
dysequilibrium
poor trunk balance
S/S of spinocerebellar lesions
limb ataxia –> ataxic gait pattern
S/S of cerebrocerebellar lesions
dysdiadochokinesia
dysmetria
action tremor
what is dysdiadochokinesia
impaired ability to perform rapid, alternating movements
what is dysmetria
type of ataxia
- lack of coordination of movement
- inability to judge distance or scale
cerebrocerebellum lesion
-affects promixal or distal limb movements
distal
