63 terms


Cerebellum Overview
Coordination and stability of body parts in both static & dynamic conditions

Comparison of intention with performance of motor actions

Toning (adjusts status of muscles to ensure sufficient accuracy & stability for accomplishing discrete/skilled motor tasks)
Cerebellar Functions
Muscle Tone
Stretch Reflex
Motor Planning
Execution of Movement
Lobes of the Cerebellar Cortex
ANTERIOR - Rostral to the Primary Fissure
POSTERIOR - Region between the Primary and Posterolateral Fissures
FLOCCULONODULAR - Structures Ventral to the Posterolateral Fissures
There are 10 (I-X)
Small Gyri on the tips of each Lobule
Rounded structures on the Inferior Surface Cerebellum flanking the Nodulus
C-shaped Midline structure of the Cerebellum that separates the Hemispheres
Surroundings of the Cerebellum
BRAINSTEM - Connected Ventrally via Cerebellar Peduncles
4TH VENTRICLE - Forms the Dorsal Roof of the 4th Ventricle and Cerebral Aqueduct
SUBARACHNOID SPACE- Filled with CSF and surrounds the rest of the Cerebellum
Cerebellar Peduncles
SUPERIOR - Connects Cerebellum to the Midbrain
MIDDLE - Connects Cerebellum to the Pons
INFERIOR - Connects Cerebellum to the Medulla
Blood Supply to the Cerebellum
Supplied by Three Pairs of Arteries arising from the Basilar/Vertebral Artery: PICA, AICA and SCA
PICA & Cerebellum
Arises form the Vertebral Arteries

SUPPLIES: Dorsolateral Medulla, Inferior Vermis and Caudal Hemispheres and Tonsils
AICA & Cerebellum
Arises from Proximal Basilar Artery and gives out Internal Auditory Arteries to the Inner Ears

SUPPLIES: Flocculus and Adjacent Area
SCA & Cerebellum
Arises from Distal Basilar Artery

SUPPLIES: Rostroventral and Dorsolateral Hemispheres, Rostral and Ventral Vermis, Deep Nuclei, Paravermis, Peduncles and Tectum of Lower Midbrain
Three Parts of Cerebellum (In Terms of Phylogenesis)
Archicerebellum - Parts, Development and Functions
INCLUDES: Flocculus, Nodulus and Lingula
DEVELOPMENT: Developed in parallel to the Vestibular Organs
FUNCTIONS: Equilibrium, Stance and Gaze Control

Paleocerebellum - Parts, Development and Functions
INCLUDES - Anterior Vermis, Pyramids and Uvula
DEVELOPMENT: Developed in parallel to the Vertebral Spine
FUNCTION: Propulsive and Trunk and Limb Movements

Neocerebellum - Parts, Development and Functions
INCLUDES - Hemispheres and Middle Vermis
DEVELOPMENT: Developed in parallel to the Cerebral Neocortex
FUNCTION: Fining tuning and coordination of movement, including fingers and toes

Higher Animals
Layers of Cerebellar Folium (Cortex)
Molecular Layer
Purkinje Cell Layer
Granule Cell Layer
Molecular Layer - Layer, Cell Types
LAYER: Outer
CELL TYPES: Stellate and Basket Cells (Inhibitory), Purkinje Cell and Golgi Cell Dendrites, Parallel Fibers of Granule Cells
Purkinje Cell Layer - Layer, Cell Types
LAYER: Middle
CELL TYPES: One layer of Purkinje Cells
Granule Cell Layer - Layer, Cell Types
LAYER: Inner
CELL TYPES: Granule Cells (Excitatory), Golgi Cells (Inhibitory) and Glomeruli

This layer contains more neurons than the entire Cerebral Cortex
White Matter of Cerebellar Folium
Located underneath the Granule Cell Layer
Cell Types of Cerebellar Cortex (Just a Hot Pic)
Purkinje Cells
DENDRITES - Molecular Layer, receive input from Climbing Fibers and Parallel Fibers
CELL BODY - Purkinje Cell Layer
AXONS - Only cell type to project through the Granule Cell Layer and act as Efferent signals from the Cerebellum (IMPORTANT)
Cerebellar Output (Important)
Is composed completely of Purkinje Cell Axons that use GABA as transmitter; therefore Cerebellar Output is Inhibitory
Granule Cells
Project axons from the Granule Layer to the Molecular Layer which then form the PARALLEL FIBERS.

Receive excitatory inputs from Mossy Fibers

They are excitatory neurons (Glutamate)
Golgi Cells
Cell bodies are located in the Granule Cell Layer and Dendrites in the Molecular Layer. These Dendrites are excited by Granule Cells, and resulting Axonal projection functions to INHIBIT the Granule Cells within the Molecular Layer.

(Feedback Inhibition, GABA)
Stellate and Basket Cells
Interneurons within the Moelcular Layer.

Excited by Parallel fibers and form Inhibitory Synpases on the Dendrites of Purkinje Cells within the Molecular Layer.
Mossy Fibers
90% of Afferent Fibers to the Cerebellum, ALL ARE EXCITATORY

Spinal Cord, Vestibular Nerve, Pontine Nuclei → Form Glomeruli that synapse on Granule Cell Bodies/Dendrites of Granular Layer
Climbing Fibers
10% of Afferent Fibers to the Cerebellum

Contralateral Inferior Olivary Nucleus → 10 Purkinje Cell Dendrites of Molecular Layer

ALL FIBERS ARE EXCITATORY, but have stronger power than Mossy Fibers.

Involved in "Error Detection & Correction"
Parallel Fibers
Axons of the Granule Cells that are in the Molecular Layer. They receive Excitatory Input from Mossy Fibers and have several outputs:

PURKINJE CELLS - Each fiber activates several
STELLATE AND BASKET - Inhibitory Interneurons activated by Parallel Fibers

*This means that of all the Purkinje Cell activated by Parallel Fibers, only some remain activated, while the rest are inhibited by Stellate/Basket
Aminergic Afferents
Modulatory fibers from:

RAPHE NUCLEI - Use Serotonin (5-HT)
LOCUS CERULEUS - Use Norepinephrine (NE)

Both have terminations in almost all layers
A bulbous expansion of distal Mossy Fibers that form Excitatory synapses on Granule Cell Dendrites within the Granular Layer.

These Dendrites are also under Inhibitory influences from Golgi Cells, however, that curb the excitement.
Deep, Paired Nuclei of Cerebellum
Fastigial, Interposed (Globose & Eboliform), Dentate, Vestibular
Fastigial Nuclei
Associated with the Vestibular Cerebellum and Spinocerebellum

FUNCTION: Antigravity & postural maintenance in standing & walking (axial muscles), modulation of saccade & smooth pursuit
Interposed Nuclei
Consists of Globose and Emoliform Nuclei

Associated with Spinocerebellum

FUNCTION: Modulation of stretch reflex (distal muscles)
Dentate Nuclei
Largest Cerebellar Nuclei

Associated with Cereberocerebellum

FUNCTION: Initiation & control (fine toning) of volitional motor activities (programming & planning)
Vestibular Nuclei
Located in the Medulla but descendant from the Cerebellum

Associated with Vestibulocerebellum

FUNCTION: Static & dynamic stabilization of gaze & posture
Inferior Cerebellar Peduncle (ICP)
All fibers are incoming EXCEPT the Cerebellobulbar Tract, which are output fibers from the Cerebellum to the ipsilateral Vestibular Nuclei

Incoming Fibers:
-Primary Vestibular Afferents
-Vestibulocerebellar Projection
-Olivocerebellar Tract
-Dorsal Spinovestibular Tracts
-Afferents from Brainstem Reticular Formation
Dorsal Spinovestibular Tracts
Fastest conducting system in the entire CNS that concerns inputs from Muscle Spindles

From Clarke's Nucleus & Accessary Cuneate Nucleus
Middle Cerebellar Peduncle (MCP)
All fibers are incoming from Contralateral Pontine Nuclei to Neocerebellar Cortices
Superior Cerebellar Peduncle (SCP)
All fibers are outgoing EXCEPT the Spinocerebellar Tract carrying information from Golgi Tendon Organs to Vermis
-ONLY tract that enters cerebellum via SCP

Contains all Cerebellar output fibers except Cerebellobulbar Tract
Feedback Loops of Cerebellum
Cerebellum-Cerebellum Loop (Triangle of Guillian-Mollaret, Cerebellum-SC Loop) & Cerebrum-Cerebellum Loop

Triangle of Guillian-Mollaret Loop
Purkinje Cells of Cerebellum → Dentate Nucleus → Decussation to Contralateral Red Nucleus of Midbrain → Inferior Olivary Complex (via Central Tegmental Tract) → Decussation of Climbing Fibers (Back to Purkinje Fibers)

Feedback Loop terminates in the same portion of the Cerebellum as where it began
Cerebellum-Spinal Cord Loop
Purkinje Cells of Cerebellum → Dentate Nucleus → Decussation to Contralateral Red Nucleus of Midbrain → Brainstem (via Rubrospinal Tract) → Decussation to the Contralateral Spinal Cord → Cerebellum

Feedback Loop terminates in the same portion of the Cerebellum as where it began
Purkinje Cells of the Cerebellum → Dentate Nucleus → Decussation to Contralateral Thalamus → Cerebral Cortex → Pons via Cerebrobulbar Tract → Decussation to Cerebellum

Feedback Loop terminates in the same portion of the Cerebellum as where it began
Cerebellar Double Crossings (Important)
All loops have Double Decussations, so that when you have a Cerebellar Lesion, all symptoms will be localized IPSILATERALLY.
Functional Parts of the Cerebellum
Vestibulocerebellum Territory
Includes Nodulus and Bilateral Flocculi
Vestibulocerebellum Phylogenesis, Inputs, Outputs, Functions and Lesion
PHYLOGENESIS: Archicerebellum

INPUTS: Primary & secondary vestibular inbuts

OUTPUTS: Purkinje Cells → Bilateral vestibular nuclei, contralateral cerebellum, brainstem reticular formation

FUNCTIONS: Maintenance of equilibrium, gaze stabilization, posture control

LESION: Distorted equilibrium (astasia, abasia, ataxia, nystagmus, tendency of falling)
Spinocerebellum Territory
Includes Vermis and Intermediate Hemispheres
Spinocerebellum Phylogenesis, Inputs, Outputs, Functions and Lesion
PHYLOGENESIS: Paleocerebellum

INPUTS: Dorsal & ventral spinocerebellar tracts, cuneocerebellar tracts (Ia fibers from Golgi organs & muscle spindles)
-Others: auditory, visual, vestibular, cerebral

-Purkinje Cells (Vermis) → Fastigial Nucleuss* → Lateral vestibular nucleus, contralateral ventrolateral thalamus & brainstem reticular formation
-Purkinje Cells (Paravermian Hemispheres) → Interposed Nucleii* → Contralateral red nucleus & Contralateral ventrolateral thalamus

FUNCTIONS: Axial & proximal muscle tone; control stretch reflexes

LESION: IPSILATERAL truncal & limb ataxia, gait disturbance, scanning speech
Cerebrocerebellum Territory
Lateral Cerebellar Hemispheres
Cerebrocerebellum Phylogenesis, Inputs, Outputs, Functions and Lesion
PHYLOGENESIS: Neocerebellum

INPUTS: Corticopontocerebellar Tract, Olivocerebellar Tract (climbing fibers)

OUTPUTS: Dentatorubrothalamic Tract

FUNCTIONS: Receives cerebral planning about voluntary movement in advance, compares planned * actual motion, and modulates pyramidal & extrapyramidal actions to ensure the precision & smoothness of complex motion

LESION: DISTAL ataxia, dysmetria, asynergia, dysdiadochokinesia, intention tremor, hypotonia, delay in initiation of motor task, inability to estimate weight
Cerebellar Lesion Symptoms
Dizziness (Vertiginous or Non-Vertiginous)
Impiared Eye Control
Gait Disturbance
Difficulty in Coordination
Illusive Perception of Motion. Results from a mismatch of predicted pattern of movement to the real status

Mismatch may occur at any level of the peripheral & central vestibular systems, while the vestibular nucleus is the fundamental structure involved
Cerebellar Lesion Signs
Abnormal Stance
Eye jerks- many different types

Many show fast & slow beating phases (direction of fast phase is used to name direction of nystagmus)
A difficulty in performing a voluntary/involuntary motor task in a coordinated manner

Caused by defected execution of intended motor action with abnormalities in direction, speed, stability & accuracy
Vestibulocerebellum Signs and Symptoms
Functions - Functions - Signs & Symptoms
Spinocerebellum Signs and Symptoms
Functions - Functions - Signs & Symptoms
Cerebrocerebellum Signs and Symptoms
Functions - Functions - Signs & Symptoms
Causes of Cerebellar Lesions
Congenital Malformations
Idiopathic and Hereditary Diseases
Trauma and Vascular Lesions
Metabolic, Endocrine, and Nutritional Disorders
Inflammatory and Autoimmune Diseases
Non-neurological Causes