Cerebellum

Cerebellum

checks the amount, degree, and fluidity of movement that the cerebral cortex gives.

Tentorium Cerebelli

invagination of the meningeal layer of the dura mater that covers and separates the cerebellum from the cerebral cortex.

Vermis

structure that connects and separates the two lobes of the cerebellum.

Cerebellar Cortex

\- gray matter

\- superficial layer

Cerebellar White Matter

inner layer where you can find subcortical gray matter or nuclei.

Gray Matter

\- made of layers

* molecular layer
* purkinje layer
* granular layer

Intercerebellar Nuclei

\- embedded within the white matter

* fastigial nuclei
* globose nuclei
* dentate nuclei
* emboliform nuclei

* Archicerebellum
* Paleocerebellum
* Neocerebellum

divisions of the cerebellum.

Archicerebellum

concerned with equilibrium because of its connection with the vestibular system.

Paleocerebellum

\- found in the anterior portion of the cerebellar hemisphere

\- concerned with stereotyped movements (recognizes distinction in gait or posture)

Neocerebellum

\- biggest part

\- important for coordinated movement

* Anterior Lobe
* Posterior Lobe
* Flocculonodular Lobe

lobes of the cerebellum.

Anterior Lobe

if viewed anteriorly it is v-shaped.

Primary Fissure

divides the anterior lobe from the rest of the lobes.

Posterior Lobe

\- middle lobe

\- lies between the primary fissure an the uvulonodular fissure

Flocculonodular Lobe

situated posterior to the uvulonodular lobe.

Layers of the Cerebellum

their primary function is to transmit neurotransmitters.

* Molecular Layer
* Purkinje Layer
* Granular Layer

layers of the cerebellum

Molecular Layer

\- superficial layer

\- contains stellate (outer) and basket (inner) cells

Stellate and Basket Cells

\- two cells present in the molecular layer

\- receives excitatory input and gives it to the other cells of the cerebellum.

Purkinje Layer

\- primary output of the cerebellar cortex

\- direction of movement: inside to outside

Purkinje Fibers

\- has dendrites that fans towards the cerebellar cortex/molecular layer (1 way transmission)

\- inhibits specific part of the cerebellum

Granular Layer

\- deepest layer of the cerebellum

\- contains parallel fibers

Parallel Fibers

\- unmyelinated

\- runs perpendicular to the purkinje fibers

\- excitatory

Golgi Cell

receives input from parallel and mossy fibers.

Intercerebellar Nuclei

\- clusters of nerve cell bodies embedded in the cerebellum

\- point of interneuron

\- serves as a “stopover” of neurons going in or out of the cerebellum

Dentate Nucleus

the largest of the cerebellar nuclei.

Emboliform Nucleus

is ovoid and is situated medial to the dentate nucleus.

Globose Nucleus

consists of one or more rounded cell groups that lie medial to the emboliform nucleus.

Fastigial Nucleus

lies near the midline in the vermis close to the roof of the fourth ventricle.

Intrinsic Fiber

\- fibers that don’t go out of the cerebellum but connects with other regions of the cerebellum

\- connection of cerebellar hemisphere

Afferent Fibers

\- perceives sensory input to the cerebellum

\- goes through the inferior and middle cerebellar peduncles

Efferent Fibers

responsible for motor output.

Mossy Fibers

\- clusters of small fibers from different parts of the CNS (outside cerebellum) and terminates in the granular cell

\- has different origins (e.g. pons, spinal cord, reticular formation, etc.)

\- termination: granular cells

Climbing Fiber

responsible for bringing information from olivary nucleus to the purkinje fibers (inferior to superior).

Cerebellum

functions:

* coordinating skilled voluntary movements by influencing muscle activity, and controlling equilibrium and muscle tone
* comparator and error correcting mechanism

* Superior Cerebellar Peduncles
* Middle Cerebellar Peduncles
* Inferior Cerebellar Peduncles

peduncles of cerebellum.

Superior Cerebellar Peduncle

peduncle connected to the midbrain.

Middle Cerebellar Peduncle 

peduncle connected to the pons.

Inferior Cerebellar Peduncle 

peduncle connected to the medulla oblongata.

* Cortico-pontocerebellar Pathway
* Cerebro-olivocerebellar Pathway
* Cerebro-reticulocerebellar Pathway

cerebellar afferent pathways.

Cortico-pontocerebellar Pathway

\- from the cerebrum to the pontine nuclei - transverse fibers to the contralateral cerebellar

\- gives afferent information from the cerebrum to the cerebellum to control the movement

Cerebro-olivocerebellar Pathway

\- from the cerebrum to the paired olivary nucleus to the cerebellum

\- subserves both (R) and (L) olivary nucleus

\- the ipsilateral olivary nucleus has fibers projecting to the contralateral cerebellum

Cerebro-reticulocerebellar Pathway

\- from the cerebrum to the reticular formation to the cerebellum

\- subserves ipsilateral cerebellum

* Globose emboliform rubral pathway
* Dentothalamic pathway
* Fastigial reticular pathway
* Fastigial vestibular pathway

cerebellar efferent pathways

Globose Emboliform Rubral Pathway

\- decussates towards the contralateral red nucleus via the superior cerebellar peduncle

\- rubrospinal tract then decussates to the contralteral side. Therefore, GER pathway subserves the ipsilateral side

Dentothalamic Pathway

\- decussates on the contalateral VPL thalamus via the superior cerebellar peduncle

\- for motor activity

Fastigial Reticular Pathway

from the fastigial nuclei to the reticular formation via the inferior cerebellar peduncle to form the reticulospinal tract ipsilaterally.

Fastigial Vestibular Pathway

\- from fastigial nucleus to the vestibular nucleus of both sides via the inferior cerebellar peduncle

\- for vestibulospinal tract; for muscle tone

Multiple Sclerosis

common cause of cerebellar pathology.

Multiple Sclerosis

condition that involves the degeneration of the oligodendrocytes.

Guillain Barre Syndrome

condition that involves the degeneration of the Schwann cells. 

Asthenia

generalized muscle weakness.

Asynergia

loss of ability to associate muscles together for complex movements.

Delayed reaction time

increased time required to initiate voluntary movement.

Dysarthia

disorder of motor component of speech.

Scanning Speech

prolonging of syllable when speaking/ prolonged pausing before speaking.

Dysdiadochokinesia

impaired ability to perform rapid alternating movement.

Dysmetria

inability to judge the distance or range of movement.

Dyssynergia

movement is performed in a sequence of component parts rather than as single smooth action.

Ataxic Gait

\- widen base of support

\- flexed hips and knee (low center of gravity)

\- no arm swinging

\- hesitation on swing phase

Hypotonia

decrease in muscle tone.

Hypermetria

overestimation of distance.

Hypometria

underestimation of distance.

Nystagmus

\- rapid, involuntary, oscillatory, back and forth movement of the eye

\- two reasons:

* cerebellum transfers information to the vestibular nuclei
* cerebellum is responsible for coordination of muscle tone due to extraocular muscle

Rebound Phenomenon

inability to halt forceful movements.

Kinetic Tremor

tremor manifests during movement.

Titubation

rhythmic oscillation of the head (axial extremity).