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what is the function of the cerebellum
- integration and coordination of signals from other areas of the brain
- assists to sequence motor activities
- monitors and corrects motor activities
- aids the cortex in planning next movements, helping to make smooth transitions from one movement to the next
- especially vital to the control of rapid muscular activities (running, typing, talking)
what is the make up of the cerebellum?
2 hemispheres separated by the "vermis", a worm-like structure
the divisions of the hemispheres of the cerebellum
- 3 major lobes
- -- anterior (paleocerebellum)
- -- middle (neocerebellum)
- -- posterior or flocculonodular (archicerebellum)
- each have a specific set of connections and set of functions with some overlap
cerebellar connections to the spinal cord, brain stem, and forebrain are represented by what cerebellar peduncles?
- inferior (restiform body)
- middle (brachium pontis)
- superior (brachium conjunctivum)
what is the structural makeup of the cerebellum?
- folia: parallel folds in the surface
- follium: outer surface of each fold formed by a layer of gray matter called the cerebellar cortex
- internal core of white matter ("tree of life")
- 4 pairs of deep cerebellar nuclei
what are the 4 pairs of deep cerebellar nuclei that lie deep to the white matter?
- medial to lateral
globose and emboliform are normally combined as the nucleus interpositus
what are the 3 cellular layers of the cerebellum?
- outer to inner
- molecular layer
- purkinje cell layer
- granule cell layer
what is the cerebellum molecular layer?
- contains stellate and basket cells; axons and dendrites of deeper cells
- receives signals from the deeper layers
what is the cerebellum purkinje cell layer?
- large flask shaped cells w/ huge dendritic branches that extend up to the molecular layer
- cells have one axon that extends down to synapse either on deep cerebellar nuclei or vestibular nuclei
what is the cerebellum granule cell layer?
- highly packed with cells
- axons extend up toward molecular layer and bifurcate
- fibers pass along folium (parallel to each other)
- synapse w/ denritic branches of purkinje cells
what cells and fibers compose the cerebellum?
- purkinje cells
- climbing fibers
- mossy fibers
- granule cell parallel fibers
- golgi cells
- basket/stellate cells
what are the purkinje cells that make up the cerebellum?
- provide inhibitory output to deep cerebellar nuclei
- long axons
- receive input from climbing and mossy fibers
what are the climbing fibers that make up the cerebellum?
- excitatory input from inferior olive
- provide 200 synapses onto one purkinje cell
- 1 fiber can fire purkinje cell to produce a "spot" of activity
what are the mossy fibers that make up the cerebellum?
- excitatory input from cord/brain stem
- synapses on granule cells which then synapse on purkinje cell (divergence - 1 fiber can influence many purkinje cells)
- receive input from widespread parts of CNS
- one fiber is not strong enough to influence purkinje cell, requires summation
what are the granule cell parallel fibers that make up the cerebellum?
- synapse on purkinje cell dendrites to form a "beam" of activity
- 1 synapse per purkinje cell
what are the golgi cells that make up the cerebellum?
- inhibitory cells in granule cell layers
- receives input from granule cell parallel fibers, mossy fibers, and climbing fibers
- inhibit the granule cells
- form a brief burst of granule cell parallel fiber activity
what are the basket/stellate cells that make up the cerebellum?
- receive input from granule cell parallel fibers
- provide lateral inhibition to "off beam" zone
what are the two major axonal systems that deliver input to the cerebellar cortex?
- Mossy fibers (synapse w/ granule cells - needs summation)
- Climbing fibers (synapse w/ purkinje cells - no need for summation)
what are the two functional divisions of the cerebellum?
- the "vestibular" cerebellum
- the "spinal" cerebellum