Lecture 12- Contributions Of Cerebellum And Basal Nuclei To Motor Function I Flashcards
What does the premotor cortex (area6) do?
- Plans movements based on sensory and visual cues
What does the supplementary motor area (area6) do?
- retrieves and coordinates memorized motor sequences
What are some functions of the motor cortex system (4)?
- provides most of the activating signals to the spinal cord
- Issues sequential and parallel commands that initiate various cord patterns
- cortical patterns are usually complex and can be learned
- cord patterns are mainly determined by heredity and are “hard-wired”
Why has the cerebellum been called a silent area of the brain?
Because electrical excitation of the cerebellum modes not cause any conscious sensation and rarely causes any motor movement
Removal of the cerebellum causes what?
Causes body movements to become highly abnormal
What are the two major roles played by the cerebellum?
- timing of motor activities
- rapid, smooth progression from one muscle movement to the next
What are some of the functions of the cerebellum (12)?
- it is not essential for locomotion
- it helps sequence motor activities
- it monitors and makes corrective adjustments to motor activities while they are being executed
- it compares actual movements with intended movements
- It aids the cortex in planning the next sequential movement(s)
- it learns by its mistakes
- It functions with the spinal cord to enhance the stretch reflex
- it functions with the brain stem to make postural movements
- it functions with the cerebral cortex to provide accessory motor functions
- it turns on the antagonist at the appropriate time
- it helps program muscle contraction in advance
- it functions mainly when muscle movements have to be rapid
What are the three lobes of the cerebellum?
- anterior lobe
- posterior lobe
- flocculonodular lobe
Which of the lobes to the cerebellum is associated with the vestibular system?
Flocculonodular lobe
What is the function of the vermis?
Location for control functions for muscle movements of the axial body, neck, shoulders, and hips
What is the function of the intermediate zone?
It is concerned with controlling muscle contractions in the distal portions of the upper and lower limbs, especially hands, feet, fingers, and toes.
What is the function of the lateral zone?
Associated with cerebral cortex with planning of sequential motor movements
- without this lateral zone, most discrete motor activities of the body lose their appropriate timings and sequencing and therefore become uncoordinated
Describe the cortex of the cerebellum.
- like the cerebral cortex, this is gray matter and consists of multiple layers of cells, dendrites, and synapses
- consists of transversely arranged narrow gyro called folia
The intracerebellar nuclei make up an inner layer of greater matter in the cerebellum. What are the following pairs of nuclei does it contain?
- dentate
- emboliform
- globose
- fastigial
All of the deep cerebellar (intracerebellar) nuclei receive signals from what two sources?
- cerebellar cortex
- the deep sensory afferent tracts to the cerebellum
What are some characteristics of the dentate nuclei, emboliform nuclei, and the glob use nuclei (3)?
- lesions in these nuclei lead to extremity ataxia
- these fibers project to the red nucleus
- related to limb musculature and fine manipulative movement
What are some characteristics of the fastigial nuclei (3)?
- lesions in this nuclei results in I trunk ataxia
- fibers project to reticular formation and vestibular nuclei
- related to postural activity and limb movements via reticulospinal and vestibulospinal tracts
Two areas of gray matter in the cerebellum?
- cortex
- intracerebellar nuclei (deep cerebellar nuclei)
What’s are the layers of the cerebellar cortex?
- granular layer
- purkinje cell layer
- molecular layer
Granular layer?
- inner most layer
- made up of granule cells, Golgi type II cells, and glomeruli
- axons of mossy fibers synapse with granular cells and Golgi type II cells in the glomeruli
Purkinje cell layer?
- middle layer
- contains Purkinje cells
Molecular layer?
- outer most layer
- contains stellar cells, basket cells, Purkinje dendrites, Golgi type II cells, and axons of granule cells (parallel fibers)
These are the only excitatory cell in the cerebellar cortex?
Granular cells
Granular cells?
- axons form parallel fibers in cortex (+)
Golgi cells?
- project from parallel fibers to granular cell bodies (-)
Basket cells?
- Project from parallel fibers to Purkinje axon hillock (-)
Stellate cells?
- Project from parallel fibers to Purkinje dendrites (-)
Both of the cells types are located in the molecular level of the cerebellar cortex?
- Basket cells
- Stellate cells
These cells provide lateral inhibition on adjacent Purkinje cells to provide damping?
- basket cells and stellar cells
Purkinje cells (5)?
- extensive dendritic branching
- receive input from parallel fibers (20,000 synapses between parallel fibers and one Purkinje cell
- project to intracerebellar nuclei (-)
- ONLY output from cortex
- output is ALWAYS INHIBITORY
Cerebellar cortex afferent pathways?
- climbing fibers
- mossy fibers
Climbing fibers(5)?
- originate from medullary olives
- make multiple synapses with Purkinje cells
- Provide high frequency bursts (complex spikes)
- “condition” the Purkinje cells
- play a role in motor learning
Mossy fibers (3)?
- originate from multiple centers in the 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
Purkinje cell axons (5)?
- the only output form the cerebellar cortex
- output is ALWAYS INHIBITORY
- GABA
- Projects to deep cerebellar nuclei and vestibular nucleus
- modulates output of cerebellum and provides synergy (regulates rate, range, and direction of movement)
How many functional units are in the cerebellar cortex?
30 million
Each functional unit of the cerebellar is centered on what?
A Purkinje cell and a deep nuclear cell
What does the primary cortex (area 4) do?
- signals motor neurons to contract skeletal muscle fibers
- signals via the corticospinal (pyramidal) tract
- execution of commands is preceded by extensive processing by the cerebellum and basal nuclei
The output from a functional unit of the cerebellar cortex comes from where?
Deep nuclear cell
Afferent inputs to the cerebellum are mainly from what?
- climbing fibers
- mossy fibers
Where do all climbing fibers originate?
Inferior olives
The nervous system uses the cerebellum to coordinate motor control function at what three levels?
- vestibulocerebellum
- spinocerebellum
- cerebrocerebellum
What is the relationship of the vestibulocerebellum to pendular movements?
- most body movements are pendulum (9swing back and forth)
- all pendular movements tend to overshoot
- appropriate learned subconscious signals from intact cerebellum can stop movement precisely at intended point (= damping system)
What are some changes that occur when the cerebellum is removed?
- movements are slow to develop
- force developed is weak
- movements are slow to turn off
