Cerebellum Flashcards
The cerebellum is responsible for what 3 things?
coordination of movements
posture & balance
tone of muscles
Where is the cerebellum located?
posterior end of brainstem
The cerebellum is a derivative of what?
Rhombencephalon (part of hindbrain)
What are the 3 lobes of the cerebellum? Give their alternative names as well.
anterior/paleocerebellum
posterior/neocerebellum
flocculus/archicerebellum
What is the paleocerebellum responsible for?
muscle tone
What is the neocerebellum responsible for?
movement coordination
What is the archicerebellum responsible for?
balance
Is cerebellar control of the motor system ipsilateral or contralateral?
ipsilateral
Describe topographic representation along the vermis.
Vermis receives motor information from the neck, shoulders, trunk, hips, eyes. Paravermal region receives sensory (particularly regarding motor function) info from the periphery (hands, feet) of the body.
How many homunculi are there in the cerebellum?
2
Damage to the primary motor cortex produces contralateral or ipsilateral motor deficit?
contralateral
What happens in the prefrontal lobe?
have idea to do something, but motor system is not activated
What happens in the premotor area?
receive idea to do something from prefrontal lobe; receives motor program from basal ganglia (after it passes through thalamus)
What happens in the basal ganglia?
receives info about movement; get motor program
What happens in the primary motor, secondary motor, and somatosensory areas?
receive motor program
What do corticospinal fibers do, broadly speaking?
travel, fire, and cause muscle contraction (movement)
How does CNS know initial position of body (necessary to get to final position)?
proprioception
What test can you do to check for working proprioception, which is necessary for movement coordination?
have patient touch index fingers in front of chest when eyes are closed
The cerebellum is a massive collector of what?
information (constantly updated)
The cerebellum is a massive collector of what?
information (constantly updated)
Is the cerebellum responsible for conscious or unconscious movement?
unconscious
What 2 structures in the brain are responsible for movement?
basal ganglia & cerebellum
What type of information does the cerebellum receive regarding movement?
info for intended movement
What structure gives the cerebellum the movement plan?
cerebral cortex
After the cerebellum receives the movement plan what happens?
movement begins: muscle contracts, spindles (sensory) fire
Once firing begins in the body and ligaments, tendons, joints, golgi, etc. fire, what happens?
copy of the movement plan is sent to cerebellum telling it how the movement is being carried out
What happens in the absence of cerebellar function?
no rapid start of movement or termination of movement; lack image & awareness
Are fibers the enter the cerebellum excitatory or inhibitory?
excitatory
What types of fibers enter the cerebellum?
mossy & climbing
Where do mossy fibers come from?
everywhere but the inferior olive
Where do climbing fibers come from?
inferior olive
Does the lateral part of the cerebellum contain a homunculus?
no
What neurotransmitter is associated with climbing fibers?
aspartate
What neurotransmitter is associated with mossy fibers?
glutamate
What neurotransmitter is associated with purkinje fibers?
GABA
What are the layers of the cerebellum, beginning with the outermost?
molecular - purkinje - granular
What type of fibers activate the deep nuclei of the cerebellum? Name their associated neurotransmitters.
mossy fibers (glutamate) & climbing fibers (aspartate)
What inhibits the deep nuclei of the cerebellum, and how?
purkinje cells via GABA
How are deep nuclei of the cerebellum activated?
directly via climbing or mossy fibers
How are deep nuclei or the cerebellum indirectly inhibited by climbing fibers?
One climbing fiber will ascend to the molecular level near the cerebellar cortex, where it will stimulate stimulate the dendrites of one purkinje cell. Activated purkinje cells release GABA onto deep nuclei, inhibiting them.
How are deep nuclei of the cerebellum indirectly inhibited by climbing fibers?
One climbing fiber will ascend to the molecular level near the cerebellar cortex, where it will stimulate stimulate the dendrites of one purkinje cell. Activated purkinje cells release GABA onto deep nuclei, inhibiting them.
How many purkinje cells do climbing cells stimulate?
one each
How many purkinje cells do mossy cells stimulate?
one mossy cell can stimulate many purkinje cells
Which fibers directly stimulate purkinje cells?
climbing fibers
Which fibers indirectly & diffusely stimulate purkinje cells?
mossy fibers
How are deep nuclei of the cerebellum indirectly inhibited by mossy fibers at the granular level?
Mossy fibers stimulate granular cells, which then sends axons to the molecular level, after which they travel to the cerebellar cortex, where they bifurcate and travel long distances all along the cortex, connecting w/ millions of purkinje cells along the way.
Which fibers terminate at the granular level?
mossy fibers
Are golgi cells excitatory or inhibitory? What do they act upon?
inhibitory; granular cells
Describe the 2 ways in which golgi cells may operate.
Mossy cell can directly stimulate the golgi cell in the granular layer to inhibit the granular cell via the release of GABA OR it can stimulate the granular cell, whose fibers at the molecular level stimulate the axon of the golgi cell, which is also in the molecular level, which then sends signals to the golgi cell body residing in the granular level to release GABA.
Where are basket and stellate cells located?
molecular level
Where are basket and stellate cells located?
molecular level
Are basket and stellate cells excitatory or inhibitory?
inhibitory
What is the purpose of stellate and excitatory cells?
to sharpen stimulation of a particular purkinje cell by dampening the the purkinje cells surrounding it, thus enhancing the stimulated cell’s neuronal signal
Where do mossy fibers terminate?
flocculus/archicerebellum
Via what nerve/fibers does the vestibular apparatus send information to the brainstem?
vestibular nerve (via CN VIII)
Describe what happens to vestibular fibers after they leave the vestibular apparatus.
they either go directly to the cerebellum or indirectly to the vestibular nuclei and then the cerebellum via the inferior cerebellar peduncle
What happens to vestibular fibers after they reach the cerebellum?
Fibers in the cerebellum go to the cortex, then stimulate the deep nuclei of the cerebellum, which send fibers to the vestibular complex. From here they then either descend as the vestibulospinal tract or ascend as the MLF.
What happens to vestibular fibers after they reach the cerebellum?
Fibers in the cerebellum go to the cortex, then stimulate the deep nuclei of the cerebellum, which send fibers to the vestibular complex. From here they then either descend as the vestibulospinal tract or ascend as the MLF.
Describe the purpose of the vestibulospinal tract.
keeps balance by activating extensor muscle (anti-gravity muscles) tone
Describe the purpose of the MLF.
internal connections of brainstem nuclei (CN III, IV, VI) created by this tract are responsible for eye movements that compensate for head movement to maintain gaze
What important structures are found in the spinocerellum?
vermis & paravermal area
What does the spinocerebellum do?
brings info from trunk & limbs to cerebellum
Which spinocerebellar tract is responsible for the lower limbs?
dorsal spinocerebellar
Which spinocerebellar tract is responsible for the upper limbs?
cuneocerebellar
What is the feedback pathway between the red nucleus and cerebellum? What is this tract called?
Red nucleus projects to cerebellum via synapse in inferior olivary nucleus (rubro-olivary projections). Cerebellum projects back to red nucleus from interposed nuclei. This is the rubrospinal tract.
Give a brief description of how fibers from/in the spine, cerebellum, and thalamus work together to produce movement.
Spinocerebellar fibers carrying information about the body ascend to the cerebellum. From the cerebellum, rubrocerebellar fibers take information to the thalamus for processing in the cerebral cortex. Corticospinal fibers descend to the body, telling it what to do/how to move.
Give a brief description of how fibers from/in the spine, cerebellum, and thalamus work together to produce movement.
Spinocerebellar fibers carrying information about the body ascend to the cerebellum. From the cerebellum, rubrocerebellar fibers take information to the thalamus for processing in the cerebral cortex. Corticospinal fibers descend to the body, telling it what to do/how to move.
Which deep nuclei of the cerebellum send fibers to the red nucleus? Where do these fibers come from?
globus & eboliform nuclei; fibers are fired off from purkinje cells
Where do you find deep cerebellar nuclei?
embedded in white matter at center of cerebellum
What type of input do deep cerebellar nuclei receive?
GABAergic inputs from purkinje cells in cerebellar cortex & excitatory inputs from mossy & climbing pathways
From where do most output fibers of the cerebellum originate?
deep cerebellar nuclei
Name the deep cerebellar nuclei.
dentate, emboliform, globose, fastigii
Where are each of the deep cerebellar nuclei located, related to the cerebellar lobes?
cerebrocerebellum - dentate nucleus
spinocerebellum - globus & emboliform nuclei (aka interposed nuclei)
archicerebellum - fastigii nucleus
What is the lateral part of the lateral hemispheres called?
neocerebellum
What happens at the neocerebellum?
cerebral & cerebellar cortices communicate
The intention to make moves involves what kind of fibers?
corticopontocerebellar
Are corticopontine fibers crossed?
yes
Are corticopontine fibers crossed?
yes
Define dysmetria.
inability to accurately control range of movement in muscular acts
Define dysdiadochokinesia.
inability to perform rapidly alternating movements
Define dysarthria.
difficulty articulating words due to emotional stress or paralysis, incoordination, or spasticity of muscles used in speaking
Kinetic tremor is another name for what?
intention tremor
Define titubation.
tremor of head & sometimes neck; staggering, stumbling gait
Which lobe does not really involve the brain?
flocculonodular
Motor execution involves which nuclei?
fastigial (vermis) & interposed nucleus (paravermal region)
Medial descending systems project from which nucleus?
fastigial nucleus
Lateral descending systems project from which nucleus?
interposed nucleus
Motor planning involves which nucleus?
dentate nucleus (cerebrocerebellum)
Projections to motor & premotor cortices come from which deep cerebellar nucleus?
dentate nucleus
Which part of the cerebellum is responsible for balance and eye movements? Which nuclei are involved?
vestibulocerebellum; vestibular nuclei
What fibers are bundled with the corticopontocerebellar tract as it travels through the middle cerebellar peduncle to get to the cerebellum?
corticospinal & corticobulbar
The inferior cerebellar tract receives what _______ fibers from ________________.
…climbing…inferior olive…
Which cerebellar peduncle mainly deals with cerebellar output?
superior
Which cerebellar peduncle mainly deals with cerebellar input?
inferior
Name the afferent pathways associated with the superior cerebellar peduncle.
ventral spinocerebellar tract, trigeminocerebellar tract, cerulocerebellar tract
Name the efferent pathways associated with the superior cerebellar peduncle.
dentatorubrothalamic tract, interpositorubrothalamic tract, fastigiothalamic tract, fastigiovestibular tract
What structures are associated with the inferior cerebellar peduncle?
restform body & juxtarestiform body
What fibers will you find at the restiform body?
afferent: dorsal spinocerebellar tract, cuneocerebellar tract, & olivocerebellar tract
What fibers will you find at the juxtarestiform body?
afferent & efferent: vestibulocerebellar fibers & cerebellovestibular fibers
What is the main purpose of purkinje cells?
they decide which information gets transmitted to cerebral cortex and which does not
Describe disinhibition.
not having purkinje cell fire at a particular time (inhibit the inhibitor)
All regions of the cerebral cortex project to ______ via __________.
…pontine relay nuclei…internal capsule…
Pontine relay nuclei relay input to _________ posterior cerebellar cortex via __________.
…contralateral…middle cerebellar peduncle mossy fibers…
Do cerebellar lesions manifest ipsilaterally or contralaterally?
ipsilaterally
Do cerebellar lesions manifest ipsilaterally or contralaterally?
ipsilaterally
Describe the crossing of fibers starting from the dentate nucleus all the way to the spinal cord.
Dentate nucleus fibers cross in decussation of superior cerebellar peduncle to reach contralateral red nucleus. Corticospinal tract crosses back again at pyramidal decussation. Double crossing occurs ABOVE spinal cord, leading to ipsilateral deficits in body at the occurance of a cerebellar lesion.
Dorsal spinocerebellar & cuneocerebellar tracts enter the _______ cerebellar peduncle to get to the _______ cortex to project to the __________.
…inferior…paramedian…interposed nuclei…
Afferent fibers involved with output to the spinal cord come from what?
vestibular receptors & vermis in fastigial nucleus
Efferent fibers involved with output to the spinal cord are in which tracts?
reticulospinal tract & vestibulospinal tract
What is the general role of the reticular formation regarding the cerebellum?
rapid response; facilitates actions to react quickly to perturbation
What NT transmitters are involved with the reticular formation? From where do they originate?
NE from locus ceruleus & serotonin from raphe complex
What do the NT of the reticular formation do in tandem with the cerebellum?
reflect mood through posture & movements
Do vestibular fibers reach the cerebral cortex?
no
Why does the inferior olive receive input from all senses?
want cerebellum to compare intention/thought (corticopontocerebellar tract) with reality (sensory info from inferior olive) in order to know which (movement) corrections to make
What types of fibers are primarily active when learning a new motor task?
climbing
How does motor learning work?
utilize climbing fibers when learning a new motor task; do this action long enough and it becomes imprinted as a learned motor task
Input from the vestibular system contains information regarding what?
position of head in space & regulation of extensor muscles
Describe the pathway of vestibulospinal & reticulospinal tracts/
vermal cortex -> fastigial nucleus -> fastigoreticulovestibular pathway -> vestibulospinal tract
What does the rubrospinal tract facilitate?
flexor responses in upper limb
Name cerebellar signs (of dysfunction).
ataxia, dysmetria, dysdiadochokinesia, ipsilateral decrease in stretch reflexes, asthenia, intention tremor, nystagmus
How does the water test work for nystagmus?
COWS - cold opposite, warm same
example - put warm water in right ear & you will see a right beat nystagmus
How does the water test work for nystagmus?
COWS - cold opposite, warm same
example - put warm water in right ear & you will see a right beat nystagmus
What divides the anterior and posterior lobes?
primary fissure
What is the folium?
smallest folding; contains all 3 cortical layers, reaches into white matter
What is the clinical signficance of the cerebellar tonsil?
it can herniate through the foramen magnum
What is the order of the deep cerebellar nuclei, laterally to medially?
dentate nucleus, emboliform nucleus, globose nucleus, fastigial nucleus
Which part of the cerebellum is the dentate nucleus associated with?
hemisphere
Which part of the cerebellum are the emboliform & globose nuclei associated with?
paravermal region
Which part of the cerebellum is the fastigial nucleus associated with?
vermis
What inputs will you find in the vermis?
visual, auditory, vestibular, spinal, trigeminal
What inputs will you find in the paravermal region?
spinal, trigeminal
What inputs will you find in the lateral hemisphere?
corticopontine
What inputs will you find in the archicerebellum?
corticopontine & vestibular
Describe the pathway of output from the dentate nucleus.
output bypasses the red nucleus to go directly to the thalamus
Which nucleus/nuclei sends/send fibers to the red nucleus?
interposed nucleus
Does the reticular formation send fibers ipsilaterally or contralaterally to the cerebellar cortex?
ipsilaterally
Name the structures involved with the ventral spinocerebellar tract.
mossy fibers, Golgi tendon organ, superior cerebellar peduncle, anterior lobe
Name the structures involved with the dorsal spinocerebellar tract.
muscle spindles, lower limbs, inferior cerebellar peduncle, nucleus dorsalis of Clarke
Name the structures involved with the cuneocerebellar tract.
muscle spindles, upper limbs, inferior cerebellar peduncle, accessory cuneate nucleus, posterior lobe
Describe corticopontine pathways.
fibers from frontal, parietal, & temporal lobes -> deep pontine nucleus -> fibers to contralateral cerebellar hemispheres
Describe cortical feedback.
dentate nucleus sends fibers to thalamus, then cerebral cortex; then get fibers sent down to tell body what to do
Describe the cerebellar/red nucleus pathway.
nucleus of Clarke -> contralateral red nucleus -> spinal cord & ipsilateral inferior olive -> contralateral cerebellum
What do you look for in cerebellar ataxia?
dysmetria, dysdiadochokinesia, gait ataxia
Describe hypotonia.
Low muscle tone; loss of excitation to lateral vestibular nucleus (from fastigial nucleus) leads to loss of excitatory input to spinal cord motor neurons. With knee jerk reflex, leg oscillates 6-8 times before coming to rest.
Describe dystonia.
sustained muscle contractions of limb, axial, or cranial voluntary muscles; see abnormal posture, repetitive/twisting movements
Cerebellar nystagmus may be caused by a lesion to either the _________ or the _______.
…vermal region…fastigial nucleus
Cerebellar disorders of the paravermal region include?
hypotonia
Cerebellar disorders of the vermal/midline region include?
nystagmus, unsteady gait, truncal dystaxia posteriorly, leg dystaxia anteriorly
Cerebellar disorders of the hemisphere include?
asynergia, dysmetria, dysdiadochokinesia, intentional tremor
What type of tumor might you find in the vermal/midline region of the cerebellum?
medulloblastoma
What type of tumor might you find in the hemispheric region of the cerebellum?
astrocytoma
What type of tumor might you find in the hemispheric region of the cerebellum?
astrocytoma
What kind of fibers are axons that arise from granular cells and bifurcate in the molecular layer perpendicular to the parasagittal plane?
parallel fibers
Definine disinhibition.
release of inhibition
Which pathway is involved with disinhibition?
Golgi cell to granule cell pathway
Describe feedback inhibition involving golgi & granular cells.
mossy fiber stimulates granular cell, sending signal up parallel fibers that activate the golgi cell, which inhibits the granular cell
Describe feed forward inhibition involving golgi & granular cells.
mossy fiber directly stimulates golgi cell, which then inhibits granular cell
What syndrome has the overall net effect of lowering overall intellectual function?
cerebellar cognitive affective syndrome
