28 - NeuroScience - Cerebellum Flashcards
Cerebellar Functions
Timing and pattern of muscles activated in limb, head and eye movement.
Contributes to balance, posture and muscle tone
Cerebellar Location
Posterior Fossa
What separates cerebellum from the cortex?
Tetorium Cerebelli
What is ventral to the cerebellum?
IVth Ventricle
What is inferior to the cerebellum?
Cisterna Magna
Vermis
Medial cortico-nuclear zone of the cerebellum
Blood supply of the posterior and inferior portions of the cerebellum
PICA
Blood supply of the superior portion of the cerebellum
SuCeA
Blood supply of the anterior portion of the cerebellum
AICA
What happens if there is a blockage of a vessel in the cerebellum?
Not much. There are anastomoses.
What happens if there’s a blockage of a major artery feeding the cerebellum (PICA, AICA, SuCeA)?
UGHGHGHGH!!!!!!
Compromise of either the nuclei themselves, or of the tracts allowing communication.
Cerebellar Divisions
Spinocerebellum
Cerebrocerebellum
Vestibulocerebellum
Spinocerebellum
Vermis & Intermediate Hemisphere
Control of limbs and trunk
Cerebrocerebellum
Lateral Hemisphere
Planning of movement+
Vestibulocerebellum
Flocculonodular Lobe
Control of eye & head movements
Balance
Deep Cerebellar Nuclei
Fastigial
Interposed
Dentate
Extrinsic Cerebellar Inputs
Mossy Fiber
Climbing Fiber
Fastigial Nucleus
The most medial of the nuclei
Receives the output of the Vermis and FlocculonodularLobe
Involved in balance and postural control, eye movements
Medial descending system
Interposed Nuclei
Between Fastigial Nucleus and Dendate Nucleus
Receives input from the intermediate hemisphere
Lateral descending system
Dentate Nucleus
Most Lateral of the nuclei
Receives its inputs from the lateral hemisphere
Fine movements in all regions of cerebral cortex
Vestibular complex
Serves as a deep cerebellar nucleus of the flocculonodular lobe.
Afferent projections from CN VIII go to vestibular complex to flocculonodular lobe, back to vestibular complex. It serves as a “nucleus”
Model of a deep cerebellar nucleus
Input hits nucleus
Projects to cerebellar cortex
Projects back to nucleus
Mossy Fiber
Inputs that come from all areas
Climbing Fiber
Inferior Olivary Nucleus is the only source!!!!!!
5 inputs to the cerebellum
Cortical Inputs (via pons) DSCT (Spinal cord afferent) VSCT (Spinal cord afferent) Lateral Reticular Nucleus Inferior Olivary Nucleus Vestibular Afferents and second order neurons from the vestibular complex
Cortical Inputs
Pontine nuclei receive inputs from all regions (especially frontal cortex)
Project via contralateral middle cerebellar peduncle, primarily to the lateral hemisphere (and dentate nucleus).
Lesions affect planning and execution of fine movements.
Spinal Cord Afferents - Dorsal Spinocerebellar Tract (DSCT)
Proprioceptive and other sensory information from FA(accesory cuneate nucleus)TL(clark’s nucleus) ascend to the cerebellum.
Project via ipsilateral inferior cerebellar peduncle to innervate vermis and intermediate hemisphere (and fastigial and interposed nuclei)
Lesions affect gait and balance
Spinal Cord Afferents - Ventral Spinocerebellar Tract (VSCT)
Another input from spinal cord conveys information about error signals from ongoing activity
Projects to various regions of the cerebellum via contralateral superior cerebellar peduncle.
Lateral Reticular Nucleus
Indirect spinal afferents
Projects to entire cerebellum via ipsilateral inferior cerebellar peduncle
Receives input from spinal cord as well as cerebral cortex and red nucleus.
Inferior Olivary Nucleus
Projects climbing fiber inputs to all regions of the cerebellum
Projects via contralateral inferior cerebellar peduncle.
Receives input from spinal cord, brainstem, cortex & feedback from cerebellum via parvocellular red nucleus
Lesions affect ALL cerebellar functions
Vestibular afferents & second order neurons from the vestibular complex
Project via inferior cerebellar peduncle to the flocculonodular lobe and vermis (via fastigial nucleus)
Inputs important for eye movements, posture & head/neck movements.
Lesions affect balance & eye movements.
5 neurons in the cerebellar cortex
Purkinje Cells Excitatory Interneurons Inhibitory Interneurons Mossy Fiber Climbing fiber
Single output neuron
Purkinje Cell
How many climbing fibers synapse on each Purkinje cell?
1
But it synapses thousands of times on that one cell.
Neurotransmitter released by purkinje cells
GABA
Thus, they inhibit their deep cerebellar nuclei
Mossy fibers synapse on which excitatory interneurons?
Granule cells
These synapse on thousands of purkinje cells
Granule cells synapse on which inhibitory interneurons?
Basket cells
Stellate cells
Granule cells synapse on which feedback inhibitor cells?
Golgi cells (receive input, and feed back inhibition back to that same granule cell)
3 Layers of Cerebellar Folia
Molecular
Purkinje
Granular
Molecular layer
Parallel fibers of granule cells synapse with purkinje cells
Inhibitory interneurons live here too
Granular Layer
Granule cells live here!!!!!
Excitatory interneurons
White matter
Inputs and outputs flow
Clarke’s Nucleus
T1 - L2
Proprioception & muscle spindle afferents from lower extremities and trunk
Gracile fasciculus synapses on thurr.
Projects out to form DSCT
Spinal Border Cells
Inputs from interneurons in many regions
Project in VSCT
Accesory Cuneate Nucleus
Trigeminal and upper extremity propriocpetion
It’s like the Clarke’s nucleus of the head and upper extremity!!!!!!
Cerebellar signs - ipsilateral or contralateral?
Ipsilateral to the lesion
Why??!?!
Double crossing!!!!
