12. contributions of cerebellum and basal nuclei to motor function Flashcards
What are functions of primary motor cortex (area 4)?
- signal motor neuron to contract skeletal muscle fibers
- uses corticospinal tract for signaling
- commands have extensive processing from cerebellum and basal nuclei
What are the functions of premotor cortex (area 6)?
- plans movements based on sensory and visual cues
What is the function of the supplementary motor area (area 6)?
- retrieves and coordinates memorized motor sequences
What are the functions of the motor cortex system?
- provide activating signal to spinal cord
- issues sequential and parallel commands that initiate carious cord patterns
- cortical patterns are complex and can be learned
- cord patterns are hereditary and hard wired
What are key functions of the cerebellum?
- timing of motor activities in rapid, smooth progression from one muscle movement to the next
- helps sequence motor activities
- monitors and makes corrective adjustments to motor activities during execution
What does the vermis separate?
- divides into intermediate zone and a lateral zone
The cerebellum is divided into three different lobes anatomically. What are they?
- anterior lobe
- posterior lobe
- flocculonodular lobe (associated with vestibular system)
What is the vermis?
- separates the intermediate zone and lateral zones
2. located for control functions for muscle movement of axial body, neck, shoulders, and hips
What is the intermediate zone?
- controls muscle contractions in distal portions of upper and lower limbs
What is the lateral zone?
- associates with cerebral cortex and plans sequential motor movements
What forms the inner layer of gray matter, and what nuclei are contained within that region?
- intracerebellar nuclei
2. dentate, emboliform, globose, fastigial nuclei pairs
Where would a lesion have to occur to cause extremity ataxia?
- dentate, emboliform, and globose nuclei
- these fibers project into red nucleus
- associate with limb musculature and fine manipulative movements
What would cause trunk ataxia?
- lesion to fastigial nucleus
What are characteristics of fastigial nuclei?
- fibers project into reticular formation and vestibular nuclei
- related to postural activity and limb movements via reticulospinal and vestibulospinal tract
What is the granular layer of the cerebellar cortex?
- innermost layer of granule cells, golgi type II cells, and glomeruli
- site where mossy fibers synapse with granular cells and golgi type II cells
What is the purkinje cell layer of the cerebellar cortex?
- middle layer of purkinje cells
What is the molecular layer of the cerebellar cortex?
- outermost layer.
2. stellate cells, basket cell, purkinje dendrite, golgi II, axons of granule cells
What are granular cells?
excitatory cells that form parallel fibers in cortex
What are golgi cells?
inhibitory cells that project from parallel fibers to granular cell bodies
What are basket cells?
inhibitory cells that project from parallel fibers to purkinje axon hillock
What are stellate cells?
inhibitory cells that project from parallel fibers to purkinje dendrites
Which cells in the cerebellar cortex provide lateral inhibition on adjacent purkinje cells to provide damping?
basket and stellate cells
What are some characteristics of purkinje cells?
- only output from cortex and is always inhibitory
- extensive dendritic branching
- project to intracerebellar (inhibitory) nuclei
What are cerebellar cortex climbing fibers?
- orginate in medullary olives
- condition purkinje cells and provide motor learning
- multiple synapse with purkinje cells
What are cerebellar cortex mossy fibers?
- originate from vestibulocerebellar, spinocerebellar, and pontocerebellar tracts
- multiple synapse on purkinje cells
- synapse on granule cells in glomeruli
What are the functions of the purkinje cell axons?
- efferent fibers that regulate rate, range, directoin or movement
- output is cerebellar cortex
- GABA neurotransmitter
What happens when mossy fibers enter the cerebellum from numerous sources?
- excitatory collaterals are sent to deep nuclear cells and synapse in granular layer with thousand of granule cells
- all originate from inferior olives
What are the regions of the cerebellum that contribute to motor control?
- vestibulocerebellum
- spinocerebellum
- cerebrocerebellum
What are characteristics of teh vestibulocerebellum?
- flocculonodular lobes and vermis
2. control balance and eye movement
What fibers are received by the vestibulocerebellum?
- vestibular system
2. oculomotor (pontocerebellar fibers)
What happens if the vestibulocerebellum is damaged or the flocculonodular lobes are damaged?
- equilibrium and postural movements disturbed
What action is the vestibulocerebellum most known for?
- relationship with pendular movements that continue to be “overshot” due to momentum
What makes up the spinocerebellum?
- vermis
2. intermediate zone
What are the functions of the spinocerebellum?
- control rate, force, range and direction of movement
What fibers/information does the spinocerebellum receive?
- motor cortex and red nucleus information
2. feedback from periphery to interpret actual movement
Where are corrective signals sent after comparison at the spinocerebellum?
- motor cortex via thalamus
2. magnocellular portion of red nucleus
What makes up the cerebrocerebellum?
lateral portion of hemispheres, that are associated with premotor, primary, and association somatosensory areas of cerebral cortex
What information does the cerebrocerebellum receive?
- corticolpontocerebellar projections
What type of movements are the cerebrocerebellum most involved with?
- skilled movement
2. speech
Where is motor imagery formed?
cerebrocerebellum
Dysmetria?
inability to properly direct movements
Ataxia?
loss of body movement
Past-pointing?
evaluates the vestibular nerves. Generally will overshoot a point while attempting to touch it
Dysdiadochokinesia?
cerebellar dysfunction with impaired ability to make movements with rapid motion changes
Dysarthria?
poor speech articulation
Cerebellar nystagmus?
eyeball tremor, when looking to one side of the head. Cerebellum damping fails or there is a flocculonodular lesion
Hypotonia?
decreased muscle tone which indicates cerebellar facilitation loss.
What are the afferent tracts to the cerebellum?
- corticopontocerebellar
- vestibulocerebellar
- reticulocerebellar
- spinocerebellar
- all form mossy fibers that terminate on granule cells in cerebellar cortex.
What is the function of the dorsal spinocerebellar tract to the cerebellum?
provides momentary status of:
- muscle contractions
- tension on muscle spindle
- proprioception
- body surface forces
What are the functions of the ventral spinocerebellar tract?
- feedback for what signals have reached the anterior spinal horns
- excited by rubrospinal and corticospinal tracts
Which axons form climbing fibers?
olivocerebellar tract to cerebellum.
What are the efferent tracts from the cerebellum?
- cerebelloreticular
- cerebellothalamocortical
- cerebellorubral
- cerebellovestibular
Where do the axons for cerebelloreticular tract run?
from fastigial nuclei to reticular nuceli in pons/medulla
Where do axons from cerebellothalamocortical tract run?
from dentate, emboliform, globose nuclei to thalamus to motor cortex
Where do axons from the cerebellorubral tract run?
dentate, emboliform, globose nuclei to red nucleus
Where do axons from the cerebellovestibular tract run?
cerebellum to the vestibular nuclei.
