Cerebellum Flashcards
What is unique about the size of the cerebellum?
small in size but very high in neuron density
- 80% of brain total neurons, only 10% of its size
What is the sensory function of the cerebellum?
subconscious proprioception (unconscious): tone and posture
What is the general anatomy of the cerebellum? Where is are the white and gray matter?
- outer gray matter (folia)
- inner white matter tracts (arborvitae)
What are the three lobes of the cerebellum?
- flocculonodular (lowest and smallest lobe)
- anterior
- posterior
What structures connect the cerebellum to the spinal cord?
three pairs of cerebral peduncles
- inferior
- middle
- superior
What information does the inferior peduncle transmit?
afferent info from the spinal cord and brainstem to the cerebellum
What information does the middle peduncle transmit?
afferent info from the pontine nuclei in the pons
What information does the superior peduncle transmit?
- mostly efferent info from the cerebellum to the thalamus and brainstem
- also afferent info from the midbrain
What are the 3 layers of the cerebellum?
- molecular (thick)
- purkinje (cell bodies of purkinje neurons here which are inhibited by GABA
- granular
after the granular layer you see white tracts
What type of brain matter makes up the molecular layer of the cerebellum?
gray matter
What nuclei is the most numerous output nuclei of the cerebellum?
purkinje neurons
What nuclei are the main source of cerebellar input?
- mossy fiber
- climbing fiber
Are mossy fibers and climbing fibers excitatory or inhibitory?
excitatory
Where do mossy fibers originate?
vestibular nuclei, spinal cord, and cerebral cortex
Where do climbing fibers originate?
contralateral inferior olivary nucleus
What movement are climbing fibers important for creating?
smooth movement
What does the inferior olivary nucleus do?
helps with motor coordination and motor learning through afferent signal it brings to the nucleus
What is the net effect of purkinje fibers and what do they do?
- net effect is inhibitory
- helps shape and smooth movement
What is the route of mossy fibers in the cerebellum?
mossy fiber > cerebellar white matter > granular cell in cerebellar cortex > purkinje cell > output
What is the route of climbing fibers in the cerebellum?
climbing fiber > cerebellar white matter > wraps around and synapses on purkinje cell > efferent output signal
What are input and output fibers of the cerebellum?
input: climbing and mossy fibers
output: purkinje cells and deep cerebellar nuclei
What are the four deep cerebellar nuclei?
- fastigal nuclei
- globose nucleus
- emboliform nuclei
- dentate nuclei
Which deep cerebellar nuclei belong to the nucleus interpositus?
- globose nucleus
- emoboliform nuclei
What role is associated with the fastigal nuclei?
- balance
What role is associated with the globose nucleus and emoboliform nucleus?
movement execution
What role is associated with the dentate nuclei?
movement planning
What vessels provide blood supply to the cerebellum?
- posterior inferior cerebellar artery (PICA)
- anterior inferior cerebellar artery (AICA)
- superior cerebellar artery (SCA)
How does ethanol intoxication work?
increased intoxication, increases the excitation of the inferior olivary nucleus, which increases the secretion of GABA, which causes purkinje output to not be delivered, which limits the shaping and smoothing of movement
What are the three functional regions of the cerebellum?
- vestibulocerebellum
- spinocerebellum
- pontocerebellum
What makes up the vestibulocerebellum?
- flocculonodular lobe and deep parts of vermis
What makes up the spinocerebellum?
intermediate zone (paravermis) and most of vermis
What makes up the pontocerebellum?
lateral hemispheres
Which deep cerebellar nuclei is associated with the pontocerebellum and what is it responsible for?
- dentate nucleus
- motor planning
What deep cerebellar nuclei is associated with the spinocerebellum and what is it responsible for?
- emboliform nucleus
- globose nucleus
- movement execution
What deep cerebellar nuclei is associated with the vestibulocerebellum and what is it responsible for?
fastigal nucleus
- balance
What are the inputs of the vestibulocerebellum?
- primary fibers from ipsilateral CN VIII
- secondary fibers from ipsilateral vestibular nuclei
What does the vestibulocerebellum have influence on?
- distribution of tone in limbs, trunk, neck, and extra ocular muscles
What are the outputs of the vestibulocerebellum?
- vestibular nuclei to influence the vestibularocular reflex and to influence body and limb tone and responses via vestibulospinal tracts
what is the role of the vestbulocerebellum?
- central to influencing and maintaining equilibrium
What happened when researchers removed the flocculonodular lobe in monkeys?
- the monkeys experienced disequilibrium, falling, wide base of support
- experienced motion sickness
- mimicked characteristics of a drunk person
What is the function of the spinocerebellum?
- role as a comparator
- interprets information on limb movement sent to cerebellum and interprets if movement is going according to plan
What are the 5 tracts of the spinocerebellum?
- dorsal spinocerebellar tract (DCST)
- ventral spinocerebellar tract (VSCT)
- cuneocerebellar tract (CCT)
- rostral spinocerebellar tract (RSCT)
- trigeminocerebellar projections
Which spinocerebellar tracts carry information from the lower limbs and lower trunk?
- dorsal spinocerebellar tract
- ventral spinocerebellar tract
Which spinocerebellar tracts carry information from the upper trunk, upper extremities, and neck?
- cuneocerebellar tract
- rostral spinocerebellar tract
Which spinocerebellar tract carries information from the head, face, and mouth?
trigeminocerebellar projections
How does the cerebellum act as a comparator?
cerebellum takes input on movement and determines if it is the correct intended movement, if not it will modify command updating the movement
What is the role of the pontocerebellum?
govern voluntary movement and motor learning
What is the pathway of afferent input to the pontocerebellum?
cerebrum > pons > cerebellum
What is the pathway of pontocerebellum output?
dentate nucleus > superior peduncle > contralateral red nucleus of the brain
or..
> contralateral VA/VL nuclei of the thalamus
What are the causes of cerebellar dysfunction?
- acute/chronic alcohol intoxication, developmental disorders, stroke, trauma
What are the characteristic symptoms of cerebellar dysfunction?
hypotonia, incoordination, intention tremor, ataxia (inability to coordinate muscles in movement), nystagmus
What is the difference between resting tremor in Parkinson’s disease patients and intentional tremor in cerebellar dysfunction patients?
- resting tremor occurs when there is no act or voluntary movement
- intention tremor occurs at the initiation of voluntary movement
What is important to remember about cerebellar damage?
- severity of cerebellar deficit may not reflect magnitude of damage
- difficult to determine location do to small space and high density
- unilateral lesions produce ipsilateral deficits
What is medulloblastoma?
- most common lesion in vestibulocerebellum
- highly malignant tumor affecting children 4-8
What are the symptoms of medulloblastoma?
listlessness, vomiting, headaches, and falling
- intracranial pressure causes swelling of optic nerve
What is spinocerebellar syndrome?
- syndrome causing difficulty controlling muscles in standing and walking
What are the symptoms of spinocerebellar syndrome?
- wide base of support
- dyscoordination of lower extremities
What is pontocerebllar syndrome?
most common cerebellar disease in humans
What causes pontocerebellar syndrome?
cardiovascular pathology, tumors, multiple sclerosis, and degenerative disease
What are the symptoms of pontocerebellar syndrome?
intention tremor, hypotonia, ataxia (inability to control muscles in movement)
What are common tests you can conduct on a patient to test their coordination?
- finger to nose/heel to shin test
- observation for dysmetria, intention tremor, decomposition of movement during voluntary movement
- rapid alternating movements to observe dysdiochokinesis
- Romberg test
- gait observation
