Cerebellum Flashcards
What are the 3 lobes of the cerebellum
Anterior, posterior, and floculonodular
What separates the cerebellum from the brainstem
4th ventricle
What are the 4 nuclei of the cerebellum from lateral to medial
Dentate, emboliform, globose, and fastigial
What are the 2 input pathways of the cerebellum
Middle and inferior peduncles
What is the output pathway of the cerebellum
Superior peduncle
What is the afferent innervation to the inferior peduncle
Vestibulocerebellar, dorsal spinocerebellar, and cuneocerebellar; also reticular formation, trigeminocerebellar, pontine nuclei, Raphe nucleus, locus ceruleus, and hypothalamus; mossy fibers, inferior olivary nucleus; climbing fibers
Where do the vestibulocerebellar afferents convey information from?
Vestibular nuclei and ganglia
Where do the dorsal spinocerebellar afferents convey information from?
lower extremity and trunk
Where do cuneocerebellar afferents convey information from?
Upper extremity
Where do trigemniocerebellar afferents convey information from?
Head and neck
Which is the only peduncle to receive afferent innervation from climbing fibers?
Inferior
What is the efferent innervation from the inferior peduncle
To the vestibular nuclei (feedback), DESCENDING MLF (medial longitudinal fasciculus), reticular formation and spinal cord
What are the afferents that go to the superior peduncle?
Ventral spinocerebellar (double crossed); mossy fibers
What does the ventral spinocerebellar afferent function in?
Conscious proprioception
What is the efferent from the superior peduncle?
Denticulothalamic tract (VL/VA) and red nucleus. Also inferior olivary nucleus, PAG, reticular formation, ASCENDING MLF, and pontine nuclei
What are the afferents to the middle peduncle
Pontocerebellar fibers (motor cortex to pontine nuclei, major input to cerebellum); mossy fibers
What is the efferent innervation from the middle peduncle
THERE ARE NONE
Which of the following afferents to the inferior cerebellar peduncle cross the midline?
A) Vestibular and cochlear nuclei (mossy fibers)
B) Inferior olivar (climbing fibers)
C) Dorsal spinocerebellar and cuneocerebellar tracts
B and C
What is the afferent fiber that crosses the midline on its way to the middle cerebellar peduncle?
Pontine nuclei’s mossy fibers; communicates corollary discharge
Which afferent to the inferior cerebellar peduncle conveys reafference
Mossy fibers of the dorsal spinocerebellar and cuneocerebellar tracts
What are the 5 afferents to the inferior cerebellar peduncle (easier names) - VIRTS
Vestibular nuclei, inferior olivary nuclei (climbing fibers), reticular formation, trigeminal nuclei, spinal cord
What is the efferent from the cerebellum
Vestibular nuclei
What is the afferent to the middle cerebellar peduncle (easier name)
Pontine nuclei (cerebral cortex)
What is the afferent to the superior cerebellar peduncle?
Anterior (ventral) spinocerebellar tract
Where do the superior cerebellar peduncle’s efferents originate?
In the deep cerebellar nuclei
Where do the superior cerebellar peduncle’s efferents project to?
Primarily to the motor areas of the cortex via the thalamus (VL/VA)
What are the microscopic layers of the cerebellum? List them from closest to the white matter to cerebellar cortex
Granular layer
Purkinje layer
Molecular layer
What do granular cells do?
Send their axons into the molecular layer as parallel fibers
What are the 3 components of the molecular layer
Stellate cells, basket cells, and parallel fibers from the granule cell axons of mossy fibers
What are the only axons that leave the cerebellar cortex, and where do they synapse?
Purkinje cells’, and they synapse on deep nuclei
What are basket cells?
Inhibitory axons that synapse on the purkinje CELL BODY
What are stellate cells?
inhibitory axons that synapse on Purkinje CELL DENDRITES - wrong in his lecture?
What is the outermost microscopic layer of the cerebellum
Molecular
How many parallel fibers synapse on each purkinje dendritic tree in the molecular layer
200,000
What is the primary neurotransmitter of the purkinje cells of the prukinje layer of the cerebellum
GABA
Where are granule cell bodies and golgi cells found?
Granular layer
What are the components of a cerebellar glomerulus
Mossy fiber terminal, granule cell dendrites, and golgi cell axons
What is the effect of stellate, basket, and Golgi cells (interneurons) on Purkinje fibers?
Inhibition
Which interneurons synapse directly on the Purkinje cells
Basket (on cell body) and stellate (on dendrites)
How do golgi cells inhibit purkinje fibers indirectly?
They receive input from parallel fibers (granule cells) and subsequently inhibit purkinje cells by suppressing the excitation of the granule cells by the mossy fibers at the glomeruli
The cerebellar cortex processes information in… rows or columns?
Rows
The cerebrum processes information in… rows or columns?
Columns
Do mossy fibers synapse directly on purkinjes?
NO
What is the major afferent input of the cerebellum
Mossy fibers
Where do mossy fibers originate?
Brainstem nuclei and spinal cord
Where do mossy fibers send collaterals?
Deep nuclei
How do mossy fibers indirectly influence purkinje cells?
each mossy fiber activates a cluster of granule cells, which makes strong, excitatory connections on purkinje cells
Describe the output of mossy fibers and granule cells
Output is high at 50-100 spikes/second, producing “simple” spikes in the Purkinjes
What is the effect of mossy fibers on the purkinje cell
modulation of the moment-to-moment firing rate
How many Purkinje cells are innervated by a single climbing fiber?
1-20, but only 1 climbing fiber per purkinje cell
How do climbing fibers orient relative to the purkinje cells
Axons of the climbing fibers wrap around the soma and proximal dendrites of the purkinje, making numerous excitatory and powerful connections
Describe the output of the climbing fibers
Low at 1 spike/second
Why do climbing fibers result in a large AP followed by numerous smaller APs (complex spike)
Despite their low output, they are numerous and powerful and cause a large influx of Ca++ in the Purkinje cell to change the membrane potential
How do climbing fibers modulate mossy fiber inputs
Via long-lasting depolarization/depression effects on the Purkinje cells
What is corollary discharge
Receiving information from the programming and execution centers of the cortex about plans for movement via INTERNAL feedback
What is reafference
Input from the peripheral sensory system about motor performance via EXTERNAL feedback pathways
where does the cerebellum project to indirectly?
Descending motor systems of the CNA via the thalamus, red nucelus, and synapses on spinal interneurons
What are the 3 functions of the cerebellum
- smooths, coordinates, and fine tunes movement
- maintains posture
- maintains equilibrium
What does damage to the cerebellum result in?
Ataxia, incoordination, wide-based gait, overshooting, and proprioception problems
What is the vestibulocerebellum associated with?
Flocculonodular lobe and vermis
What is the direct input of the vestibulocerebellum
Semicircular canals and otolithic organs
What is the indirect input of the vestibulocerebellum
Vestibular nuclei, lateral geniculate, superior colliculus, pontine nuclei
What is the output of the vestibulocerebellum
Fastigial nucleus
Where does the output of the vestibulocerebllum project back to?
Vestibular nuclei
What is the function of the vestibulocerebellum
To control axial and proximal limb muscles associated with balance and posture; also to control eye movement and coordination of head and eye movements
Does the vestibulocerebellum control ongoing execution of movement ipsilaterally or contralaterally?
Ipsilaterally
What are the 2 divisions of the spinocerebellum
Vermis and intermediate hemisphere
Where does the spinocerebellum receive somatosensory input from
Proximal (vermis) and distal (intermediate) spinal afferents; also auditory, visual, and vestibular afferents
Describe the output of the spinocerebellum
Direct and indirect mossy fiber pathways via interposed nucleus to red nucleus and distal regions of the motor cortex
What is the function of the spinocerebellum
Distal motor control and ongoing execution of movement IPSILATERALLY
The spinocerebellum uses sensory feedback to control _______________
Muscle tone
Lesions of the spinocerebellum result in what condition?
HYPOtonia
Which hemispheres make up to cerebrocerebellum
Lateral cerebellar hemispheres
Where does the cerebrocerebellum receive cortical afferents from?
Pontine nuclei to the contralateral hemisphere
Describe the output of the cerebrocerebellum
Output via the dentate nucleus and the VL of the thalamus, which then projects back to motor and premotor regions of the cerebral cortex
What is the function of the cerebrocerebellum
To coordinate initiation, planning, and timing of movements as well as precision control of rapid movements and fine dexterity
Lesions of the the dentate or overlying cerebellar cortex cause 4 specific deficits, what are they?
- delay in initiation and termination of voluntary movements
- terminal tremor at the end of a movement
- Temporal coordination disorders across multiple joints
- spatial coordination disorders of hand and finger muscles
The dentate output pathway is indirect to the cortex via _________
Thalamus
The dentate output pathway is direct to ___________
Red nucleus
The dentate output pathway provides feedback to _________ (3 things)
Olivary nuclei, pontine nuclei, and reticular formation
The emboliform pathway is indirect to the cortex via _______________
thalamus
The emboliform output pathway is direct to the ___________
red nucleus
The function of the dentate output pathway is ____________
Motor planning and initiation
The emboliform output pathway provides feedback to _______________________
olivary nuclei, pontine nuclei, and reticular formation
The function of the emboliform output pathway is _____________
Limb position and movement
The globose output pathway is indirect to the cortex via _______________
Thalamus
The globose output pathway is direct to __________
red nucleus
The globose output pathway provides feedback to ___________
Olivary nuclei, pontine nuclei, and reticular formation
What is the function of the globose output pathway
Axial skeleton and posture
The fastigial output pathway is indirect to ___________
Cortex and oculomotor nuclei (MLF)
The fastigial output pathway is direct to __________
central gray
The fastigial output pathway provides feedback to ____________
Vestibular nuclei, olivary nuclei, and reticular formation
The fastigial output pathway is indirect to spinal interneurons via ___________
Vestibular nuclei
The function of the fastigial output pathway is ________________
Head, neck, and eye
How does motor learning take place in the cerebellum?
Climbing fibers “learn” to depress action of parallel fibers on Purkinje cells, resulting in modulation of mossy fiber input at the level of the Purkinje cell via heterosynaptic interation
What does depression of purkinje cell output in motor learning result in?
Tonic inhibitions at the level of the deep nuclei, thereby “releasing” the deep nuclei to facilitate the learned response
What does motor learning at the level of the cerebellum help reduce?
Mismatch between actual movements and intended response during repetitive tasks
Define hypotonia
Diminished resistance to passive limb displacement; lack of check; results in overshooting and excessive rebound
Define ataxia
Delay in initation of movement, errors in range and force of movements (dysmetria), and errors in the regularity and rate of repetitive movements (dysdiadochokinesia)
Define intention tremor
Errors in position, most noticeable at the end of movements where the greatest precision is required
Do lesions of the cerebellum produce contralateral or ipsilateral disorders?
Ipsilateral
Where are the double crosses of the cerebellar output pathways?
SCP and corticospinal tract
What sort of disorders do lesions in the vermis and intermediate zones produce?
Axial and truncal disorders (errors in posture “titubation,” gait, and possibly speech “dysarthria”)
What do lesions in the lateral zones of the cerebellum result in?
Delays in initation and poor coordination of multijoint movements
Which cerebellar lesions are the most severe?
Those of the deep nuclei or superior cerebellar peduncle
