Cerebellum

Question 1

The cerebellum is situated:

Answer 1

posterior cranial fosa, separated from the cerebrum by a fibrous membrane (tentorium cerebelli)

Question 2

It has two hemispheres (right and left) divided by:

Answer 2

vermis

Question 3

Separated by two fissures:

Answer 3

o Primary fissure→ Separates anterior and posterior
lobes
o Posterolateral fissure→ Separates posterior and
floculonodular lobes

Question 4

Grey matter (cell bodies) is found in:

Answer 4

the folia (folds) of the cortex and in the deep cerebellar nuclei
o Dentate nucleus
o Emboliform nucleus
o Globose nucleus
o Fastigial nucleus

Question 5

White matter (myelinated axons) are found in :

Answer 5

arbor vitae

Question 6

vermal and paravermal areas function:

Answer 6

o Vermal area receives sensory information from the
trunk, neck and most of the head
o Paravermal area receives sensory information from the limbs and the lateral head

Question 7

Cerebrocerebellum :

Answer 7

Found in the lateral hemispheres of the cerebellum Contains the dentate nucleus
o Co-ordinates muscles and plans future movements

Question 8

Vestibulocerebellum :

Answer 8

Found in the floculonodular lobe
Contains the fastigial nucleus
Maintains balance

Question 9

Functions of the cerebellum :

Answer 9

Balance
Muscle Tone
Co-ordination of movements
Motor Learning

Question 10

Main job of cerebellum :

Answer 10

The cerebellum’s main job is that of neural sharpening (the fine tuning of the motor response→ Most important stimulus is taken care of first)
This is achieved by regulating Deep Cerebelar Nuclear firing through an intricrate circuitry involving two types of afferent fibers

Climbing Fibers
Carry proprioceptive muscle information from the inferior olives through the inferior cerebellar peduncle
Involved in motor learning
Release aspartate (stimulatory neurotransmitter)
Enter the cerebellum and synapse directly onto both:
o Deep Cerebellar Nuclei→ Overall stimulatory effect o Purkinje Cells→ Overall Inhibitory effect

Mossy Fibers
Carry sensory information from all over the body via various pathways (see below)
Carry motor command information from the pontine nuclei through the middle cerebellar peduncles Release glutamate (stimulatory neurotransmitter)
Enter the cerebellum and synapse onto both:
o Deep Cerebellar Nuclei→ Overall stimulatory effect o Granule Cells→ Mixed effect
Granule cells send axons to the molecular layer where they synapse onto:
o Stellate + Basket cells→ Overall stimulatory effect Through inhibition of Purkinje cells
o Purkinje fibers→ Overall inhibitory effect
Mossy cells and granule cells can also synapse onto Golgi cells. These inhibit granule cells, further regulating the system

Question 11

SUPERIOR CEREBELLAR PEDUNCLES efferent fibers :

Answer 11

Dentothalamic
From dentate nucleus to:
o Contralateral thalamus
o Thalamus sends information to cortex

Dento-rubro-thalamic
From dentate nucleus to:
o Contralateral red nucleus
o Red nucleus sends informtation to:
Thalamus → Cortex
Contralateral rubrospinal tract→ activates flexor
muscles

Cerebellovestibular
Purkinje fibers directly to vestibular nuclear complex o Sends motor fibers to extensor muscles through
vestibulospinal tract
o Activates contralateral medial longitudinal
fasciculus (connects CN III, IV + VI for eye co- ordination)

Question 12

SUPERIOR CEREBELLAR PEDUNCLES afferent fibers :

Answer 12

Ventral spinocerebellar tract
Carries proprioceptive information of joints, tendons and ligaments from below L2/L3 to the cerebellum
o Aids movement co-ordination and balance

Rostral cerebellar tract
Carries proprioceptive information of joints, tendons and ligaments from cervical spine and upper limbs to the cerebellum
o Aids movement co-ordination and balance

Tectocerebellar tract
Carries visual and auditory information from the tectum (superior and inferior colliculi)
o Allows quick responses to visual and auditory stimuli

Question 13

MIDDLE CEREBELLAR PEDUNCLES fibers :

Answer 13

Corticopontocerebellar fibers (afferent)
Transmits original motor plan from the contralateral cortex through the pontine nuclei
o Allows for:
Motor learning
Future movement planning

Question 14

INFERIOR CEREBELLAR PEDUNCLES
Afferent fibers (into the cerebellum)

Answer 14

Dorsal spinocerebellar tract
Carries proprioceptive information of spindle fibers from spinal levels C8-L2/L3 to the cerebellum
o Aids movement co-ordination and balance

Cuneocerebellar tract
Carries proprioceptive information of spindle fibers from cervical spine and upper limbs
o Aids movement co-ordination and balance

Vestibulocerebellar tract
Carries information about acceleration from the inner ear (passes through vestibular nuclear complex)
o Aids with maintaining balance and equilibrium

Olivocerebellar tract
Carries information about movement timing and proprioception from the contralateral inferior olives to the cerebellum
Become climbing fibers
o Thought to be involved in motor learning

Reticulocerebellar tract
Carries all sensory information from the reticular formation to the cerebellum

Question 15

INFERIOR CEREBELLAR PEDUNCLES
Efferent fibers (out of the cerebellum)

Answer 15

Cerebelloreticular
Carries motor information from the cerebellum to the
reticular formation
o Medullary Tract→ Flexion of muscles o Pontine Tract→ Extension of muscles

Cerebellovestibular
Purkinje fibers directly to vestibular nuclear complex o Sends motor fibers to extensor muscles through
vestibulospinal tract
o Activates contralateral medial longitudinal
fasciculus (connects CN III, IV + VI for eye co- ordination)

Question 16

Cerebellum is supplied by three pairs of cerebellar arteries

Answer 16

Superior cerebellar artery – branch of basilar artery, supplies the superior surface of the cerebellum

Anterior inferior cerebellar artery – branch of basilar artery, supplies the anterior part of the inferior surface of the cerebellum

Posterior inferior cerebellar artery – branch of vertebral artery, supplies the posterior part of the inferior surface of the cerebellum