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physio - e2 - lecture slides > L3-Contributions of Cerebellum to Motor Function > Flashcards

L3-Contributions of Cerebellum to Motor Function Flashcards

1
Q

general functions of cerebellum

A
  • the cerebellum plays major roles in the timing of motor activities and in rapid, smooth progression from one muscle movement to the next
  • its not essential for locomotion
  • helps sequence motor activities
  • monitors and makes corrective adjustments to motor activities while they are being executed
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2
Q

true or false: electrical excitation of the cerebellum causes conscious sensation and motor movement

A

false; does not cause any conscious sensation and rarely causes any movement

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3
Q

what happens if the cerebellum is removed?

A

it causes the body to become highly abnormal

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4
Q

describe what the cerebellar functions are:

A
  • compares actual movements with intended movements
  • aids cortex in planning next sequential movement
  • learns by its mistakes
  • functions with SC to enhance stretch reflex
  • functions with brain stem to make postural movement
  • 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
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5
Q

what is the anatomical organization of the cerebellum

A
  • two hemispheres separated by vermis: each divided into an intermediate zone and a lateral zone.
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6
Q

what 3 loves is it divided into?

A

anterior lobe
posterior lobe
flocculondular lobe (associated w vestibular system)

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7
Q

describe the vermis

A

location for control functions for muscle movements of the axial body, neck, shoulders, and hips

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8
Q

describe the intermediate zone

A

concerned with controlling muscle contractions in the distal portions of the upper and lower limbs, especially hands, feet, fingers, and toes.

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9
Q

describe the lateral zone

A

associated with cerebral cortex with planning of sequential motor movements

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10
Q

describe the gray matter of the cerebellum

A

cortex: consists of cells, dendrites and synapses

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11
Q

describe the intracerebellar nuclei

A

these make up an inner layer of gray matter and include the following:

dentate
emboliform
globose
fastigial

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12
Q

describe the dentate, emboliform, and globose nuclei

A
  • lesions in these nuclei = extremity ataxia
  • these fibers project to the red nucleus
  • related to limb musculature and fine manipulative movement
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13
Q

describe the fastigial nuclei

A
  • lesion in this nucleus –> trunk ataxia
  • fibers project to reticular formation and vestibular nuclei
  • related to postural activity and limb movements via reticulospinal and vestibulopsinal tracts
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14
Q

what are the layers of the cerebellar cortex?

A

granular layer
purkinje cell layer
molecular layer

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15
Q

describe the granular layer

A
  • innermost 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
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16
Q

describe the purkinje cell layer

A
  • middle layer

- contains purkinje cells

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17
Q

describe the molecular layer

A
  • outermost layer
  • contains stellate cells, basket cells, purkinje dendrites, golgi type II cells, and axons of granule cells (parallel fibers)
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18
Q

what are the cells in the cerebellar cortex

A
  • granular cells: axons from parallel fibers in cortex (+)
  • golgi cells: from parallel fibers to granular cell bodies (-)
  • basket cells: from parallel fibers to purkinje axon hillock (-)
  • stellate cells: from parallel fibers to purkinje dendrites (-)
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19
Q

whats something to note about basket cells and stellate cells?

A

they provide lateral inhibition on adjacent purkinje cells to provide damping

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20
Q

describe the purkinje cells

A
  • extensive dendritic branching
  • receives input from parallel fibers (20K between parallel fibers and one purkinje cell)
  • project to intracerebellar nuclei (-)
  • ONLY output from cortex
  • OUTPUT IS ALWAYS INHIBITORY
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21
Q

what are the afferent, in cerebellar cortex?

A

climbing fibers and mossy fibers

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22
Q

describe the climbing fibers

A
  • 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
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23
Q

describe the mossy fibers

A
  • 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
24
Q

which ones are the efferent neurons in cerebellar cortex? describe them

A

purkinje cell axons

  • only output from cerebellar cortex
  • output is always inhibitory
  • GABA
  • projects to deep cerebellar nuclei and vestivular nucleus
  • modulates output of cerebellum and provides synergy (regulates rate, range, and direction of movement)
25
Q

describe the functional units of the cerebellar cortex

A
  • 30 million functional units in cerebellar cortex
  • each functional unit is centered on a purkinje cell and a corresponding deep nuclear cell
  • 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
26
Q

in regards to the cerebellar cortex, what do the mossy fibers do?

A

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

27
Q

what about granule cells?

A

they send axons to the outer cerebellar surface; axons branch in two directions parallel to folia

28
Q

where do purkinje dendrites project to?

A

parallel fibers

29
Q

what excites and inhibits nuclear cells?

A
  • direct stimulation by climbing and mossy fibers excites deep nuclear cells
  • purkinje cell signals inhibit deep nuclear cells
30
Q

what else functions are inhibitory cells?

A

basket cells and stellate cells

31
Q

what does the nervous system use cerebellum for?

A

to coordinate motor control functions at three levels:

  • vestibulocerebellum
  • spinocerebellum
  • cerebrocerebellum
32
Q

what does the vestibulocerebellum consist of? whats its functions?

A
  • consists of flocculonodular lobes and vermis

- functions in control of balance and eye movements

33
Q

further describe the vestibulocerebellum

A
  • receives fibers from vestibular system and oculomotor system (pontocerebellar fibers)
  • sends output pimarily to vestibular system
34
Q

what happens if theres loss of flocculonodular lobes?

A

extreme disturbance of equilibrium and postural movements

35
Q

desribe the relationship of vestibulocerebellum to pendular movements

A
  • most body movements are pendular
  • all pendular movements tend to overshoot (why?)
  • appropriate learned subconscious signals from intact cerebellum can stop movement precisely at intended point (=damping system)
36
Q

what changes occur when cerebellum is removed?

A
  • movements are slow to develop
  • force developed is weak
  • movements are slow to turn off
37
Q

describe vestibulocerebellar syndrome

A
  • starts with abnormal eye movement, including nystagmus
  • progressive genetic disease of flocculondular lobe
  • vertigo, tinnitus
  • ataxia
  • eventually fine motor skills are lost
38
Q

what is the general function and what does the spinocerebellum consist of?

A
  • consists of mostly vermis and intermediate zone

- functions in synergy: control rate, force, range, and direction of movement

39
Q

where does the spinocerebellum receive info from?

A
  • receives info from motor cortex and red nucleus telling cerebellum intended sequential plan of movemebt for the next few fractions of a second
  • feedback information from periphery telling cerebellum what actual movements result
40
Q

what two sources of info does it compare and where does it send corrections to?

A
  • motor cortex via thalamus

- magnocellular portion of red nucleus

41
Q

what are the functions of the cerebrocerebellum?

A
  • consists of lateral parts of hemisphere
  • mostly associated with the premotor and the primary and association somatosensory areas of the cerebral cortex
  • receives corticopontocerebellar projections
  • involved in coordination of skilled movement and speech
  • plans as much as tenths of a second in advance of actual movements: referred to as “motor imagery”
42
Q

what are the afferent tracts to cerebellum?

A
  • corticopontocerebellar
  • vestibulocerebellar
  • reticulocerebellar
  • spinocerebellar (dorsal and ventral)
  • all these tracts form the mossy fibers that terminate on the granule cells in the cerebellar cortex (+)
  • olivocerebellar
43
Q

describe the corticopontocerebellar

A
  • motor and premotor cortices/ somatosensory cortex –> pontine nuclei –> lateral divisions of cerebellum
  • main link between cortex and cerebellum
44
Q

where do the vestibulo- and reticulocerebellar terminate?

A
  • flocculonondular lobes

- primarily in the vermis

45
Q

describe spinocerebellar

A
  • dorsal and ventral

- transmits signals at 120 m/sec

46
Q

describe the dorsal spinocerebellar

A
  • muscle spindles –> ipsilaterally in vermis and intermediate zones
  • apprise cerebellum of momentary status of:
    muscle contractions
    degree of tension on the muscle spindles
    positions and rates of movements of body parts
    forces acting on surfaces of the body
47
Q

describe the ventral spinocerebellar

A
  • terminates both ipsilaterally and contralaterally
  • excited by signals coming from: cortex via corticospila and rubrospinal tracts; internal motor pattern generators within spinal cord
48
Q

what does the ventral spinocerebellar tell the cerebellum?

A
  • which motor signals have arrived at the anterior horns

- this feedback = efference copy of the anterior horn motor drive

49
Q

describe the olivocerebellar tracts

A
  • neurons project from inferior olivary nuclei (in medulla) to purkinje cell dendrites (+) and to intracerebellar nuclei
  • axons form climbing fibers
  • climbing fiber causes a single, prolonged action potential to each purkinje cell with which it connects (one climbing fiber per 5-10 Pc’s)
50
Q

what is a complex spike?

A

each signal starts out as a strong spike and is followed by a series of weak secondary spikes

51
Q

true or false: mossy fibers send (+) signals to granule cells

A

T

52
Q

list and describe the efferent tracts from cerebellum

A
  • cerebelloreticular: fastigial nuclei –> reticular nuclei in pons and medulla
  • cerebellothalamocortical: dentate, emboliform, globose nuclei –> thalamus –> motor cortex
  • cerebellorubral: dentate, emboliform, globose nuclei –> red nucleus
  • cerebellovestibular: cerebellum –> vestibular nuclei
53
Q

what can damage to the cerebellum lead to?

A
  • dysmetrai (inability to judge distance and when to stop)
  • ataxia (uncoordinated movement)
  • adiadochokinesia ( inability to perform rapid alternating movements)
  • past pointing
  • movement tremors
  • cerebellar lesion gait (staggering, widebase walk)
  • falling
  • cerebellar hypoplasia (weak muscles)
  • ataxic dysarthria (slurred speech)
  • nystagmus (abnormal eye movement)
  • ballistic movemebts (dystonia)
54
Q

what are the symptoms of cerebellum disorders?

A
  • lack of muscle control and coordination
  • ataxia
  • slurred speech and difficulty talking
  • abnormal eye movement
  • headaches
55
Q

what are the causes?

A
  • genetic
  • tumor,
  • poisons
  • injury
  • cerebral palsy
  • MS
  • stroke
  • infections

physio - e2 - lecture slides (8 decks)

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