Cerebellum - Lecture 5 Flashcards
What is the vermis (cerebellum)?
The vermis is a worm like band that runs down the midline connecting the two hemispheres of the cerebellum
What is the folia (cerebellum)?
The area around the vermis. Has folds that increase the surface area. Allows for a greater number of neurons to be located within the cortical layers
What/where is the cerebrocerebellum?
From outside edge to in line with the floculus. Receives input directly from the cerebral cortex. Concerned with regulation of highly skilled movement
What/where is the spinocerebellum?
At the tip of the cerebellum. The only part that receives direct input from the spinal cord. Concerned with regulating movement of distal/proximal muscles as well as certain eye movements
What/where is the vestibulocerebellum?
Bottom part of cerebellum contains nodulus and flocculus. Receives input from the vestibular nuclei in the brainstem. Primarily concerned with the vestibular-ocular reflex and regulation of balance
Where is gray matter found in the cerebellum?
Found in the outer cortex and in the deep cerebellar nuclei within the white matter
What are the 3 deep cerebellar nuclei?
Fastigial nucleus, interposed nuclei, dentate nucleus
What does the superior cerebellar peduncle do?
Connects the deep cerebellar nuclei to the midbrain, diencephalon and cerebrum.
Consists mainly of motor fibres leaving for the brain
What does the middle cerebellar peduncle do?
The largest peduncle, and connects the cerebellar hemispheres to the pons.
They consist of both motor and sensory tracts leading to the cerebellum
What does the inferior cerebellar peduncle do?
Connects the cerebellar cortex to the medulla oblongata. Is the smallest and most complex peduncle.
Consists of both motor and sensory fibres; ascending and descending tracts from the spinal cord
What are the cerebellar inputs (see diagram for reference)
Pons/Pontine nuclei (via middle cerebellar peduncle)
Red nucleus -> Inferior olive, spinal cord, vestibular nuclei (via inferior superior cerebellar peduncle)
Discuss the cerebellar somatotopic maps??
Two maps of the body, one in the anterior lobe and one in the posterior lobe
Cerebrum concerned with contralateral representation
Cerebellum concerned with ipsilateral representation
What are the 3 cerebellar output pathways?
Cerebrocerebellum -> dentate nucleus -> pre-motor cortex (motor planning)
Spinocerebellum -> interposed and fastigial nuclei -> motor cortex and brainstem (motor execution)
Vestibulocerebellum -> vestibular nuclei -> lower motor neurons in spinal cord and brainstem (balance and VOR)
Describe the pathway from the cerebellar cortex to the primary and premotor cortex
Cerebellar cortex -> deep cerebellar nuclei (dentate/interposed) -> VL complex -> primary motor and premotor cortex
Nuclei to VL complex by superior cerebellar peduncle, up VL and can also go down to superior colliculus (see diagram)
What is a purkinje cell?
Consists of a cell body and a huge dendritic tree that is perpendicular to the surface
The sole output of the cerebellar cortex
What is a climbing fibre?
One of the two ways afferent information reaches the purkinje cells
Climbs up the efferent axon of the purnkinje cell and then clambers over the dendrites
Originates from the inferior olive in the brainstem
What are mossy fibres?
Second type of afferent system to deliver information to the purkinje cells
Incoming fibres enter the lower levels of the cortex and branch go form large terminal structures - these synapse with granule which send axons to the surface where they bifurcate to form parallel fibres
What are parallel fibres?
Thin linear axons that run perpendicular to the dendrites of the purkinje cells
Form side connections (contrasts to the climbing fibres) as each parallel fibre comes in contact with large numbers of purkinje cells
How is the climbing fibres anatomy suited to its function?
Extraordinarily precise, allows for the integration of specific and real errors
How is the anatomy of the mossy fibre influencing its function?
Non specific, allows for the association with of general patterns of activity (motor learning
What are the two types of interneurons present in the cerebellum?
Basket cells - parallel fibres that inhibit the purkinje cells
Golgi cells - parallel fibres that inhibit granule cells, therefore acting at the input rather than the output
What are some classical cerebellar impairments?
Ataxia
Asynergia - dysmetria, intention tremor, decomposition of movement, dyschiadokinosis, scanning speech
Impairment of execution
Hypotonia
Rebound
What is ataxia?
Shaky and unsteady movements of body, and limbs lacking overall coordination
What is asynergia?
Lack of coordination of all kinds of movement
What is dysmetria?
The inability to place limb at correct location
What is vestibular ocular reflex gain? Use example with minifying glasses.
In normal case, the head and the eyes move in a coordinated manner to keep image on the retina
When the VOR is out of register, the eyes move too far in relation to the image movement on the retina when the head moves
VOR gain reset occurs after a certain amount of time - the eyes now move smaller distances in relation to head movement to compensate
