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Chapters 12 Motor System Cerebellum

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Cerebellum, pons, and medulla oblongata sit in the Posterior cranial fossa. 6. Cerebellar Anatomy ... In posterior fossa under tentorium cerebelli. Lobes ... – PowerPoint PPT presentation

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Title: Chapters 12 Motor System Cerebellum


1
Chapters 12 Motor System Cerebellum
  • Chris Rorden
  • University of South Carolina
  • Norman J. Arnold School of Public Health
  • Department of Communication Sciences and
    Disorders
  • University of South Carolina

2
Function of Cerebellum
  • Error Control Device - Monitor, Quality Control
  • Monitors outputs to muscles from motor cortex and
    sensory signals from receptors
  • Compares the efferent project plan with execution
    at motor action site
  • Considers related factors and makes adjustments

3
Cerebellum
  • 50 of brains neurons, 10 of volume
  • Can change movements as necessary
  • E.G. Walking or talking
  • Does not reach conscious awareness
  • Muscle synergy or coordination monitored
  • Important in running, speaking - all fluid
    movements

4
tentorium cerebelli
  • "tent of the cerebellum"
  • dura mater that separates the cerebellum from the
    inferior portion of the occipital lobes.

5
Posterior Cranial Fossa
  • Fossa is a depression or cavity in the bone
  • Cerebellum, pons, and medulla oblongata sit in
    the Posterior cranial fossa

6
Cerebellar Anatomy
Seen from feet
  • Located dorsal to pons and medulla
  • In posterior fossa under tentorium cerebelli
  • Lobes
  • Floccular Nodular(small fluffy mass)
  • Anterior
  • Posterior

Anterior lobe (H)
Posterior lobe (I)
7
Flattened Cerebellum
  • Longitudinally separated into hemispheres and
    cortices
  • Median (Vermal)
  • Vermisworm
  • Paramedian (Paravermal
  • Lateral

8
Cerebellum
Paramedian
Primary Fissure
Median
Posterior Superior Fissure
Horizontal Fissure
Prepyramidal Fissure
Posterolateral Fissure
9
Cerebellar Nuclei (Nuclei deep cluster of
neurons)
  • Dentate nucleus
  • Largest, communicates through cerebellar peduncle
  • Carries information important for coordination of
    limb movements (along with the motor cortex and
    basal ganglia)
  • Emboliform nucleus (medial side of the nucleus
    dentatus)
  • Regulates movements of ipsilateral extremity
  • Globose nucleus
  • Regulates movements of ipsilateral extremity
  • Fastigial nucleus
  • Regulates body posture
  • Is related to the flocculo nodular lobe

10
Dentate Nucleus
Dentate Nucleus
Pontine Projections
Superior Cerebellar Peduncle
Pons
11
Somatotopic Organization
  • Tactile information
  • Ipsilateral anterior lobule
  • Bilateral paramedian lobules
  • Cerebral Cortex and Cerebellum have similar
    representations
  • Motor representation
  • Same area as sensory mapping
  • May have auditory and visual processing

12
Transverse Cerebellar Regions
  • Floccular nodular lobe (Archicerebellum )
  • Oldest, related to vestibular part of VIII
  • Regulates equilibrium through vestibulospinal
    tract
  • Anterior lobe (Paleocerebellum)
  • Rostral to Primary Fissure
  • General Sensory Receptors
  • Concerned with muscle tone and walking
  • Posterior lobe (Neocerebellum)
  • Newest and Largest, Receives afferent projections
    from contralateral sensorimotor cortex
  • Projects to contralateral motor cortex
  • Functions in coordination of fine and skilled
    movements

13
Longitudinal Cerebellar Regions
  • Vermis
  • Contributes to body posture
  • Paravermal region
  • Regulates movements of ipsilateral extremities
    (e.g. walking)
  • Lateral Zone
  • Regulates skilled movements of ipsilateral
    extremity (e.g. tying your shoe)

14
Cerebellar Connection
  • Three Peduncles
  • Inferior afferent mediate sensorimotor input
    to the cerebellum
  • Middle afferent same as above
  • Superior efferent transmit output from the
    cerebellum to the brainstem and on to the
    thalamus, motor cortex, and spinal cord
  • Varied afferents to Cerebellum
  • spinal cord
  • brainstem
  • motor cortex
  • AfferenetEfferent Ratio 401
  • For each going from cerebellum to body, 40 coming
    in

15
Afferent Pathways (Inferior)
  • Vestibulocerebellar Tract
  • Info From Semicircular Canals Through Inferior
    Peduncle
  • Maintains Upright Posture
  • Dorsal Spinocerebellar Tract
  • Info From Reticular Nuclei (involved in
    regulation of sleep, respiration, heartbeat,
    etc.)
  • Unconscious Proprioception From Muscle Spindles,
    Golgi Tendons and Tactile Receptors

16
Afferent Pathways (Inferior 2)
  • Reticulocerebellar Tract
  • Info From Cerebral Cortices, Spinal Cord,
    Vestibular Complex, and Red Nucleus
  • Olivocerebellar Tract
  • Info From Spinal Cord Through Olivary N to
    Contralateral Cerebellar Hemisphere
  • Source of Climbing Fibers for Direct Input to
    Cerebellum
  • Cuneocerebellar Tract
  • Mediate Proprioception From Upper Limbs and Neck

17
Afferent and Efferent Projections
Thalamus
Red nucleus
Superior Cerebellar Peduncle
Middle Cerebellar Peduncle (pontocerebellar
fibers)
Inferior Cerebellar Nucleus (olivocerebellar
fibers)
18
Afferent Pathways (Middle)
  • Info From Pontine Nuclei From Opposite Cerebral
    Cortex, Visual and Auditory Inputs
  • To Opposite Cerebellar Hemisphere

19
Efferent Pathways
  • Arise From Cerebellar Nuclei
  • Dentate nucleus
  • Emboliform nucleus
  • Globose Nucleus
  • Through Superior Cerebellar Peduncle to
  • Red Nucleus (Brainstem)
  • Thalamus
  • Motor Cortex

20
Cerebellar Cortex
  • Structured in Three Parallel Layers
  • Molecular
  • Purkinje
  • Connecting Surface and Deep Cerebellar Nuclei
  • Source of All Efferent Fibers
  • Cerebellar Cortex
  • Granular
  • Have Mossy Fiber Axons to Purkinje Axons

21
Clinical Considerations
  • Signs of Dysfunction
  • Impaired Muscle Synergy
  • Reduced Muscle Tone
  • Evident in Skilled Tasks
  • Ataxia
  • Lack of Order and Coordination in Activities
  • Slow Movement (Bradykinesia)
  • Mild Muscular Weakness (Asthenia)
  • Asynergia
  • Speech difficulties (Ataxic Dysarthria)
  • affects respiration, phonation, resonance and
    articulation, but most pronounced in articulation
    and prosody.

22
Clinical Considerations 2
  • Dysdiadochokinesia
  • Clumsiness in Alternating Movements
  • Tapping, Speech Sound
  • Dysarthria
  • Ataxic Dysarthria
  • Scanning Speech
  • Slurred and Disjointed Speech
  • Dysmetria
  • Error in Judgment of Range and Distance of Target
  • Undershooting or Overshooting

23
Clinical Considerations 3
  • Intentional Tremor
  • Accessory Movement During Volitional Task
  • vs. Parkinsons Disease Where Tremor Lessens
    During Volitional Movement
  • Hypotonia
  • Reduced Resistance to Passive Stretch
  • Rebounding
  • Inability to Predict Movement
  • Cannot Hold Back Movement
  • Disequilibrium
  • Unsteady Gait, Body Wavering

24
Cerebellar Pathologies
  • Cerebrovascular Accident (CVA)
  • Thrombotic, embolic or hemorrhagic
  • Vertebrobasilar Artery
  • Toxicity
  • Chronic Alcoholism
  • Progressive Cerebellar Degeneration
  • Friedrich's Ataxia Autosomal Recessive Heredity
    Degenerative Condition
  • Combined Sensory and Motor Dysfunctions
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