Flashcards in Cerebellum And Motor Function Deck (75)
What area is the pre motor cortex? What does it do?
-plans movements based on sensory and visual cues
What area is the supplementary motor area? What does it do?
-retrieves and coordinates memorized motor sequences
What are the four functions of the motor cortex system?
1. Provides most of activating signals to spinal cord
2. Issues sequential and parallel commands that initiate various cord patterns
3. Cortical patterns are usually complex and can be learned
4. Cord patterns are mainly determined by heredity and are hard wired
What are the general functions of the cerebellum?
-timing of motor activities and in rapid smooth progression from one muscle movement to the next
-not essential for locomotion
-helps sequence motor activities
-monitors and makes corrective adjustments to motor activities while they are being executed
-removal of cerebellum causes body movements to become abnormal
What are some specific functions of the cerebellum as outlined in lecture?
-compares actual movements with intended movements
-aids cortex in planning next sequential movement
-learns by its mistakes
-functions with spinal cord to enhance the stretch reflex
-functions with brainstem to make postural movements
-functions with cerebral cortex to provide accessory motor functions
-turns on antagonist at appropriate time
-helps program muscle contraction in advance
-functions mainly when muscle movements have to be rapid
What divides the two hemispheres of the cerebellum?
-divided into an intermediate zone and lateral zone
What are the three lobes of the cerebellum? Anterior to posterior. Which is associated with the vestibular system?
-flocculonodular lobe (associated with vestibular system)
What is the vermis responsible for?
-location for control functions for muscle movements of axial body, neck, shoulders, and hips
What is the intermediate zone responsible for?
-concerned with controlling muscle contractions in the distal portions of upper and lower limbs especially hands, feet, fingers, and toes
What is the lateral zone responsible for?
-associated with cerebral cortex with planning of sequential motor movements
How is the cortex of the cerebellum organized?
-consists of transversely arranged narrow gyro called folia
What are the intracerebellar nuclei?
-make up inner layer of gray matter and include the following pairs of nuclei:
What are the dentate, emboliform, and glubose nuclei responsible for?
-related to limb musculature and fine manipulative movement
-fiber project to the red nucleus
-lesions in these nuclei result in extremity ataxia
What is the fastigial nuclei responsible for?
-related to postural activity and limb movements via reticulospinal and vestiibulospinal tracts
-fibers project to reticular formation and vestibular nuclei
-lesion in the nucleus results into trunk ataxia
What are the 3 layers of the cerebellar cortex? What are some features of each?
-granular layer: innermost layer
+made up of granule cells, Golgi type II cells, glomeruli
+axons of most fibers synapse with granular cells and Golgi type II cells in the glomeruli
-Purkinje cell layer: middle layer
+contains Purkinje cells
-molecular layer: outermost layer
+contains stellate cells, basket cells, Purkinje dendrites, Golgi type II cells, and axons of granule cells (parallel fibers)
What are granular cells?
-axons form parallel fibers in cortex (+)
What are Golgi cells?
-project from parallel fibers to granular cell bodies (-)
What are basket cells?
-project from parallel fibers to Purkinje axon hillock (-)
What are stellate cells?
-project from parallel fibers to Purkinje dendrites (-)
What two cells provide lateral inhibition on adjacent Purkine cells to provide dampening?
-basket cells and stellate cells
What are some characteristics of Purkinje cells in the cerebellar cortex?
-extensive dendritic branching
-receive input from parallel fibers
-project to intracerebellar nuclei (-)
-only output from cortex
-output is always inhibitory
What are the two different afferent neurons in the cerebellum?
-climbing fibers and mossy fibers
What are some characteristics of climbing fibers?
-originate from medullary olives
-make up multiple synapses with Purkinje cells
-provide high frequency bursts (complex spikes)
-condition the Purkinje cells
-play a role in motor learning
What are some characteristics of mossy fibers?
-originate from multiple centers in brainstem and spinal cord, including vestibulocerebellar, spinocerebellar, and pontocerebellar tracts
-make multiple synapses on Purkinje cells and result in simple spikes
-synapse on granule cells in glomeruli
What is the efferent neuron of the cerebellum?
-Purkinje cell axons
+only output from cerebellar cortex
+output is always inhibitory
+projects to deep cerebellar nuclei and vestibular nucleus
+modulates output of cerebellum and provides synergy (regulates range, rate, and direction of movement)
Describe a functional unit of the cerebellar cortex.
-30 million functional units
-each unit is centered on a Purkinje cell and a corresponding deep nuclear cells
-output from a functional unit is from a deep nuclear cell
-afferent inputs to the cerebellum are mainly from the climbing and mossy fibers
-all climbing fibers originate from the inferior olives
-mossy fibers enter cerebellum from a variety of sources (send excitatory collaterals to deep nuclear cells and then synapse in granular layer with thousands of granule cells)
-granule cells send axons to outer cerebellar surface, axons branch in two directions parallel to folia
-dendrites of Purkinje cells project to these parallel fibers
-direct stimulation by climbing and mossy fibers excites deep nuclear cells. Purkinje cell signals inhibit deep nuclear cells
-basket cells and stellate cells also function as inhibitory cells
What are the three systems used to coordinate motor control?
Describe the vestibulocerebellar system.
-consists of flocculonodular lobes and vermis
-functions in control of balance and eye movements
-evolved at about the same time as vestibular system
-receives fibers from vestibular system and oculomotor system (pontocerebellar)
-sends out primarily to vestibular system
-loss of flocculonodular lobes -> extreme disturbance of equilibrium and postural movements
How is the vestibulocerebellum related to pendular movements?
-most body movements are pendullar (swing back and forth) -> have tendency to overshoot
-appropriate learned subconscious signals from cerebellum can stop movement precisely at intended point -> damping system