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Physio II Exam 2 > Lecture 11 - Cerebellum Control of Motor Function > Flashcards

Lecture 11 - Cerebellum Control of Motor Function Flashcards

1
Q

Cerebellum: Functions

A
  • Electrical excitation of the cerebellum does not cause any conscious sensation and rarely causes any motor movement. •Removal of the cerebellum causes body movements to become highly abnormal. •The cerebellum plays major roles in the 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
  • 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 brain stem 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
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2
Q

Anatomical Organization of Cerebellum

A

Two hemispheres separated by vermis: •Each hemisphere is divided into an intermediate zone and a lateral zone. Anatomically divided into three lobes (Anterior →Posterior): •Anterior lobe: •Posterior lobe: •Flocculonodular lobe: •Associated with vestibular system

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3
Q

Vermis:

A

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

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4
Q

Intermediate zone

A

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

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5
Q

Lateral zone:

A

Associated with cerebral cortex with planning of sequential motor movements

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6
Q

Gray Matter of Cerebellum

A

cortex

intracerebellar nuclei

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7
Q

Cortex:

A
  • Like the cerebral cortex, this is gray matter and consists of multiple layers of cells, dendrites, and syapses.
  • Consists of transversely arranged narrow gyri called foli
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8
Q

Intracerebellar nuclei:

A 
These make up an inner layer of gray matter and include the following pairs of nuclei: 
•Dentate 
•Emboliform 
•Globose 
•Fastigial
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9
Q

Dentate nuclei, Emboliform nuclei, 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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10
Q

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 vestibulospinal tracts
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11
Q

Layers in Cerebellar Cortex

A

Granular
Purkinje cell layer
Molecular layer

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12
Q

Granular Layer of cerebellarcortex

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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13
Q

Purkinje cell layer of cerebellar cortex

A
  • Middle layer

* Contains Purkinje cells

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14
Q

Molecular layer of cerebellar cortex

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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15
Q

Cells in Cerebellar Cortex

A

Granular, Golgi, basket, stellate, purkinje

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16
Q

Granular cells

A

Axons form parallel fibers in cortex (+)

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17
Q

Golgi cells

A

Project from parallel fibers to granular cell bodies (-)

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18
Q

Basket cells

A

Project from parallel fibers to Purkinje axon hillock (-)

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19
Q

Stellate cells

A

Project from parallel fibers to Purkinje dendrites (-)

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20
Q

Purkinje cells

A
  • 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
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21
Q

Cerebellar Cortex: Afferents

A

climbing fibers and mossy fibers

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22
Q

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
23
Q

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

Cerebellar Cortex: Efferents

A

Purkinje cell axons:

  • Only output from 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)
25
Q

Functional Units of Cerebellar Cortex

A

30 million units
-each centered on purkinje cell and adj 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. •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

26
Q

3 Levels of Motor Control Function

A
  • Vestibulocerebellum
  • Spinocerebellum
  • Cerebrocerebellum
27
Q

Vestibulocerebellum

A
  • Consists of flocculonodular obes and vermis
  • Functions in control of balance and eye movements
  • Evolved at about the same time as vestibular system
  • Receives fibers from:
  • Vestibular system
  • Oculomotor system (pontocerebellar fibers)
  • Sends output primarily to vestibular system.
  • Loss of flocculonodular lobes → extreme disturbance of equilibrium and postural movements.
28
Q

Relationship of vestibulocerebellum to pendular movements:

A
  • Most body movements are pendular(swing back and forth)
  • All pendular movements have tendency to overshoot (WHY?)
  • Appropriate learned subconscious signals from intact cerebellum can stop movement precisely at intended point (= damping system).
  • Changes that occur when cerebellum is removed:
  • Movements are slow to develop.
  • Force developed is weak.
  • Movements are slow to turn off.
29
Q

VestibulocerebellarSyndrome

A
  • Starts with abnormal eye movement including nystagmus
  • Progressive genetic disease of the flocculonodular lobe
  • Vertigo, tinnitus
  • Ataxia
  • Eventually fine motor skills are lost
30
Q

Spinocerebellum

A
  • Consists mostly of vermis and intermediate zone
  • Functions in synergy: control of rate, force, range and direction of movement
  • Receives:
  • Information from motor cortex and red nucleus telling cerebellum intended sequential plan of movement for the next few fractions of a second.
  • Feedback information from periphery telling cerebellum what actual movements result
  • Compares two sources of information and sends corrections to:
  • Motor cortex via thalamus •Magnocellular portion of red nucleus
31
Q

Cerebrocerebellum

A
  • Consists of lateral parts of hemispheres
  • 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”
32
Q

Corticopontocerebellar

A
  • Motor and premotor corJces/Somatosensory cortex → Pontine nuclei → Lateral divisions of cerebellum
  • Main link between cortex and cerebellum
  • Lesions result in muscle weakness
33
Q

Vestibulocerebellar

A

Terminates in flocculonodular lobes

34
Q

Reticulocerebellar

A

Terminates primarily in vermis

35
Q

Spinocerebellar

A
  • Dorsal and ventral

* Transmit signals at 120 m/sec

36
Q

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 movement of parts of the body
  • Forces acting on surfaces of the body
37
Q

Ventral spinocerebellar

A
  • Terminates both ipsilaterally and contralaterally
  • Excited by signals coming from:
  • Cortex via corticospinal and rubrospinal tracts
  • Internal motor pattern generators within spinal cord
  • Tells cerebellum:
  • Which motor signals have arrived at the anterior horns
  • This feedback = efference copy of the anterior horn motor drive
38
Q

Olivocerebellar

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 (up to one second) action potential on each Purkinje cell with which it connects (one climbing fiber per 5-10 Purkinje cells.
  • Each signal starts out as a strong spike and is followed by a series of weak secondary spikes (= complex spike)
  • Note that mossy fibers (discussed previously) send (+) signals to granule cells.
39
Q

Efferent Tracts from Cerebellum

A

Cerebelloreticular, cerebellothalamocortical, cerebellorubal, cerebellovestibular

40
Q

Cerebelloreticular

A

Fastigial nuclei → reticular nuclei in pons and medulla

41
Q

Cerebellothalamocortical

A

Dentate, emboliform, globose nuclei → thalamus → motor cortex

42
Q

Cerebellorubral

A

Dentate, emboliform, globose nuclei → red nucleus

43
Q

Cerebellovestibular

A

Cerebellum → vestibular nuclei

44
Q

Cerebellum: Disorders

A

Symptoms •Lack of Muscle Control and Coordination •Difficulty Walking = Ataxia •Slurred Speech and Difficulty Speaking •Abnormal Eye Movement •Headaches
Causes •Genetic •Tumor •Poisons •Head Injury •Cerebral Palsy •Multiple Sclerosis •Infections •Stroke

45
Q

Dysmetria

A

The inability to judge distance and when to stop

46
Q

Ataxia

A

Uncoordinated movement

47
Q

Adiadochokinesia

A

The inability to perform rapid alternating movements

48
Q

Intention Tremors

A

Movement tremors

49
Q

cerebellar lesion gait

A

Staggering, wide based walking

50
Q

cerebellar hypoplasia

A

weak muscles

51
Q

ataxic dysarthria

A

slurred speech

52
Q

nystagmus

A

abnormal eye movements

53
Q

dystonia

A

ballistic movements

Physio II Exam 2 (8 decks)

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