ICL 9.2: Cerebellum & Disorders Flashcards
what are the overall functions of the cerebellum?
it’s responsible for the coordination and stability of body parts in both static and dynamic conditions
it precisely adjusts the status of muscles to ensure sufficient accuracy and stability for accomplishing discrete and skilled motor tasks
it also compares the intended action with what was actually executed to make sure they match up
cerebellar functions include:
1. equilibrium
- muscle tone
- stretch reflex
- motor planning
- execution of movement
so cerebellar lesions would result in characteristic symptoms and deficits
what ventricle is the cerebellum related to?
the cerebellum forms the roof of the 4th ventricle
how is the cerebellum connected to the brainstem?
cerebellum connects with brainstem to its dorsal aspect via 3 pairs of peduncles = superior, middle and inferior to the midbrain, pons and medulla, respectively
what are the 3 lobes of the cerebellum?
- anterior lobe = the region rostral to the primary fissure
- posterior lobe = the region between the primary and dorsolateral fissure
- flocculonodular lobe = the structures ventral to the dorsolateral fissure
folia is the tree looking part of the cerebellum and there’s also 10 lobules but you don’t need to know the specifics
which 3 arteries supply the cerebellum?
- PICA = posterior inferior cerebellar arteries
supplies the dorsolateral medulla, inferior vermis and caudal hemispheres
- AICA = anterior inferior cerebellar arteries
supplies flocculus and inner ears
- SCA = superior cerebellar arteries
supplies other parts of the cerebellum and lower midbrain
these are all branches of the vertebrobasilar arterial system
go look at slide 14 so you know which areas of the cerebellum would be effected in a stroke of a certain artery
what is the archicerebellum?**
it includes:
- bilateral flocculi
- nodulus
- lingual
responsible for equilibrium, stance, balance and gaze control = vestibulocerebellum
parallel to the development of vestibular organs
what is the paleocerebellum?**
- anterior vermis
- pyramids
- uvula
responsible for propulsive and stereotypes axial motions = spinocerebellum
parallel to the development of vertebral spine
what is the neocerebellum?**
- hemispheres
- middle vermis
responsible for fine toning and precise coordination of distal kinesis aka distal fine motion = cerebrocerebellum
parallel to the development of cerebral neocortex
what are the 3 cellular layers of the cerebellar cortex?
- molecular layer (outer)
- purkinje cell layer = 1 cell thick (middle layer)
- granule cell layer (inner layer)
what are the 5 cell types found in the cerebellar cortex?
molecular layer:
1. stellate cell
- basket cell (modulatory cells)
purkinje cell layer:
1. purkinje cell (cell body in this layer but the dendrites extend into molecular layer)
granule cell layer:
1. golgi cell
- granule cell (excitatory; glutamate)
what are purkinje cells? what NT do they release?
it’s the only cells that give out efferent projections from cerebellar cortex and it’s found in the perkinje cell layer
looks like a radish with lots and lots of roots growing out of it
they are inhibitory neurons that release GABA
what are granule cells? what NT do they release?
they’re found in the granular layer of the cerebellum
the cell bodies are compacted in the granule cell layer while the axons form the parallel fibers that travel to the molecular layer
granule cells receive excitatory inputs from mossy fibers
they are excitatory neurons that release glutamate
what are golgi cells? what NT do they release?
they’re found in the granular layer of the cerebellum
their cell bodies are found in the granule cell layer while the dendrites are found in the molecular layer
they give feedback inhibition to granule cells after being activated by them
they are inhibitory neurons that release GABA
what are stellate and basket cells? what NT do they release?
they are found in molecule cell layer
the local interneurons are in the molecular layer
they inhibit purkinje cells when activated by the parallel fibers –> so they’re inhibitory neurons that release GABA or taurine
what are the 2 types of afferent fibers entering the cerebellum?
- climbing fibers
2. mossy fibers
what are climbing fibers?
one of the two types of afferent fibers entering the cerebellum – they only account for a small proportion of afferent fibers though
they are the fibers coming from the contralateral inferior olivary nucleus –> they end at the dendrites of the Purkinje cells in the molecular layer (each purkinje cell recieves input from only one climbing fiber but each climbing fiber can stimulate 10 purkinje cells)
note: superior olivary nucleus is auditory while inferior olivary nucleus is the cerebellum
they are ALL excitatory and they have a stronger depolarization power than the mossy fibers
what are the mossy fibers?
one of the two types of afferent fibers entering the cerebellum – they account for 90% of all incoming fibers to the cerebellum!
the fibers come from the spinal cord, vestibular nerve and pontine nuclei and they end at the cell bodies of the granule cells in the granule cell layer
ALL are excitatory
what are parallel fibers?
excitatory fibers that travel longitudinally in the molecular layer
they are all the axon branches of the granule cells extending into the molecular layer!
these fibers connect with multiple purkinje cells and activate a bunch of them
what is the glomerulus?
a bulbous expansion of distal mossy fiber forms excitatory synapses to the surrounding granule cell dendrites which are also postsynaptic to the inhibitory terminals of Golgi cells
so it’s a small, intertwined mass of nerve fiber terminals in the granular layer of the cerebellar cortex – it consists of post-synaptic granule cell dendrites and pre-synaptic Golgi cell axon terminals surrounding the pre-synaptic terminals of mossy fibers
so it’s a modulatory effect on the mossy fibersbecause granular cells are excitatory while golgi cells are inhibitory
what are all the different fiber connections in the cerebellum?
the climbing fibers excite the purkinje cells and then the purkinje cells inhibit one of the central nuclei of he cerebellum or the golgi cell
mossy fibers excite the granular cells and then the granular cells excite the purkinje fibers
the golgi cells inhibit the granular cells
what are the 5 deep nuclei of the cerebellum?
- dentate nucleus (the largest and most lateral cerebellar nuclei)
- emboliform nucleus
- globose nucleus
- fastigal nucleus (most medial)
- vestibular nuclei
these nuclei are the major synapsing points of the purkinje fibers
the emboliform nucleus, globose nucleus and festival nucleus are the medial nuclei associated with the vermis while the dentate is the lateral nuclei associated with the cerebellar hemispheres
interposed nucleus = globose + emboliform nuclei
which part of the cerebellum are each of the deep nuclei of the cerebellum associated with?
- fastigial nucleus = spinocerebellum
- interposed nucleus = spinocerebellum
- dentate nucleus = cerebrocerebellum
- vestibular nuclei = vestibulocerebellum
spinocerebellum is the middle part of the cerebellum, cerebrocerebellum is the lateral parts of the cerebellum and the vestibulocerebellum is the floculonodulous
which cerebellar peduncles are incoming vs. outgoing from the cerebellum?
the inferior and middle cerebellar peduncles are incoming (except the cerebellobulbar tract from the inferior cerebellar peduncles)
the superior cerebellar peduncle fibers are all outgoing except the ventral spinocerebellar tract
what is the function of the inferior cerebellar peduncles?
contains mainly input fibers:
1. primary vestibular afferents
- vestibulocerebellar projection
- olivocerebellar tracts = climbing fibers from contralateral olivary nucleus
- dorsal spinovestibular tracts = inputs from muscle spindles
- afferents from brainstem reticular formation
contains a small amount of output fibers from the cerebellobulbar tract which go to the ipsilateral vestibular nucleus
don’t really need to know this….