Lecture 3 - Cerebellum Flashcards
What is the cerebellum and what does it do?
-determines whether or not the movement we are performing is correct by incorporating information from the vestibular system about balance and the spinal system about posture and where you are in space
What are the spins?
neurological phenomenon when you cannot figure out where your body is in space while you are rotating
What does the cerebellum also potentially play a role in?
language processes since it is enlarged in humans and in dolphins which communicate via echolocation
What are the three cerebellar peduncles?
superior, middle, inferior
What are the three deep nuclei of the cerebellum?
fastigial, interposed, and dentate
What do cerebellar purkinje cells have?
great arborization and alot of dendritic branching
Why is the cerebellum caudal to the brainstem?
many of the vestibular or motor nuclei that project from the brainstem to the cerebellum are found there
How many hemispheres does the cerebellum have and what is it separated by?
-two hemispheres
-separated by the vermis
What is the job of the cerebellar peduncles?
-the physical connection between the cerebellum and the brain stem and are -the major connection pathways between the cerebellum and the rest of the brain
How many cell layers does the cerebellum have?
three cell layers
How many functional divisions or lobes exist for the cerebellum and what is their overall role?
there are three lobes; two send output from the cerebellum and receive input from their corresponding lobe or division
What is the name of the lateral lobes of the cerebellum and what is its role?
cerebrocerebellum; implicated in language verb choice, reasoning such as quantitative and spatial; motor planning and executing higher functions
What is the name of the medial lobe or vermis and what is its role?
spinocerebellum; key in posture and proprioception and coordinates movement so you can stay upright and have movements and has a body map
What is the name of the lobe found at the flocculonodular lobe?
vestibulocerebellum and is the balance hub of the cerebellum; receives afferent and efferent projections from vestibular nuclei in the brainstem
What lobe and division sends input to the dentate nucleus and what is the dentate nucleus role?
-the lateral lobes or the cerebrocerebellum
-responsible for motor feedback to execute motor commands that may be implicated in higher order functions like language and verb usage
-largest of the three nuclei
-efferent fibers that leave this nucleus modulate motor function, visuospatial function and conscious thought
What lobe or division sends input to the interposed nucleus and what is the interposed nucleus role?
-the vermis or spinocerebellum
-implicated in posture and proproprioception and coordination of movement
-has two divisions: the globose and emoliform nucleus
What lobe or division sends input to the fastigial nucleus and what is the role of the fastigial nucleus ?
-the vestibulocerebellum or the flocculonodular lobe
-implicated in balance
How many different cell types are in the three layers of the cerebellum?
five different cell types
What are the three layers of the cerebellum from outer to inner?
-molecular layer
-purkinje layer
-granular layer
What are the two cell types in the molecular layer and are they inhibitory, excitatory, or modulatory?
-stellate cells (like astrocytes)
-basket cells (form synapses)
-inhibitory
What cell types are present in the purkinje layer and are they inhibitory, excitatory, or modulatory?
purkinje cells
inhibitory - GABAergic
are the output of the cerebellum since all cellular input converges onto purkinje cells which synapse onto deep nuclei which are the output of the cerebellum
What cell types are present in the granule layer and are they inhibitory, excitatory, or modulatory?
-golgi cells - inhibitory - round in shape
-granule cells (most abundant cell type in the CNS) - excitatory
What are the two types of fibers present in the cerebellum?
-climbing fibers
-mossy fibers
What are climbing fibers?
-fire complex spikes
-originate in the inferior olive of the medulla
-enter the cerebellum via the inferior peduncle to synapse onto neurons in the deep nuclei as well as purkinje cells
What are mossy fibers?
-fire simple spikes
-originate in brainstem nuclei and enter the cerebellum via the middle and inferior peduncles and synapse onto granule cells which are excitatory
-outnumber climbing fibers
What is a parallel fiber?
axons which extend from granule cells and synapse onto purkinje cells or deep nuclei
From what cells can a purkinje cell receive input from?
basket cell/stellate cells, climbing fiber, mossyfiber—>granule cells–>parallel fibers,
What kind of spikes do climbing fibers fire versus mossy fibers?
-climbing fibers - complex spikes (since it wraps around multiple times the purkinje cell; repetitive depolarizations before hyperpolarizing)
-mossy fibers - simple spikes
What is the motor error feedback loop and what role does the cerebellum play in it?
-the cerebellum detects a difference between the actual movement and the movement and generates an error term and generates then it will try to minimize the error term with the feedback loop provided while the movement is being performed
What is the proposed mechanism for learning in the cerebellum by Marr and Albus?
LTD or long terms depression due to gabaergic neurons in the cerebellum; cerebellum will prune away the neurons it does not need making the neurons it does need stronger in comparison
What is the VOR?
-the vestibulo-ocular reflex
-an eye reflex that the cerebellum plays an important role in and it is activated when the body is spinning and causes the intraocular muscles to contract in order to cause counteractive eye movements to stabilize the visual field by causing inhibition of one set of extraocular muscles and exciting the other set of extraocular muscles on the other side
What are saccades?
the counteractive eye movements that are made to stabilize the visual field when spinning
