Functional Anatomy Of The Cerebellum

Question 1

The cerebellum functions as a …

Answer 1

Rapid, corrective feedback loop smoothing and coordinating movements

Question 2

The motor plan leaves…

Answer 2

The cortex (intended movement) and goes to the basal nuclei and cerebellum (actual movement)

Question 3

The cerebellum overvie w

Answer 3

Programmes ballistic movements - precise timing and appropriate patterns of skeletal muscle contraction
Compares intended and actual movement
Corrects ongoing movement
Activity occurs subconsciously
Motor learning patterns shift from the conscious to unconscious

Question 4

Information from:

Answer 4

Somatosensory
Visual, auditory, vestibular, proprioceptive

Question 5

Describe the anatomy of the cerebellum

Answer 5

Situated in post cranial fossa and covered superiorly by the tentorium cerebellum
Located dorsal to the pons and medulla
Accounts for 11% of the brain mass
Two cerebellar hemispheres L&R joined medially by the vermis
Internal white matter - arbor vitae
External grey matter folia - transversely arranged gyri
Each hemisphere divided in to 3 lobes by primary and posterolateral fissures

Question 6

What are the 3 lobes of the cerebellum

Answer 6

Anterior
Posterior
Flocculonodular

Question 7

A tier and posterior lobes are dived further into…

Answer 7

Zones
Vernal Zoe - occupies the vermis
Intermediate (paravermal) zone - lies on each side of the vermis, occupying the medial regions of the cerebellar hemispheres
Lateral zone - lies lateral to the intermediate zone

Question 8

What are the cerebellar peduncles

Answer 8

Three paired fibre tracts connect the cerebellum to the brainstem
Superior - connect cerebellum -> midbrain
Middle - connect cerebellum -> post and to the axis of the brainstem
Inferior - connect cerebellum -> medulla

Question 9

Describe the superior peduncles

Answer 9

To the midbrain
Fibres originate from neurons in the deep cerebellar nuclei and communicates with the motor cortex via the midbrain and the Diencephalon (thalamus)

Question 10

Describe the middle peduncles

Answer 10

To the pons
Cerebellum receives info advising it of voluntary motor activities initiated by motor cortex

Question 11

Describe the inferior peduncles

Answer 11

To the medulla
Afferent conveying sensory info from muscle proprioceptors thorughout the body and from the vestibular nuclei of the brainstem (medulla oblongata)

Question 12

What are the 3 major function divisions of the cerebellum

Answer 12

Vestibulocerebellum - composed of the flocculonodular lobe
Spinocerebellum - composed of th vermis and paravermal zone
Cerebrocerebellum - composed of the lateral zones of the cerebellar hemispheres

Question 13

Anterior lobe is responsible for …

Answer 13

The regulation of muscle tone, coordination of skilled voluntary movement

Question 14

Posterior lobe is responsible for…

Answer 14

Planning and initiation of voluntary activity

Question 15

Flocculomodular lobe is responsible for

Answer 15

Maintenance of balance, control of eye movement

Question 16

What are the spinocerebellar tracts

Answer 16

Posterior (dorsal) - enters cerebellum via inf cerebellar peduncle
Anterior (ventral) - enters cerebellum via the superior cerebellar peduncle
Cuneoerebellar tract - enters cerebellum via inf cerebellar peduncle

Question 17

Describe the inferior olivary nuclei

Answer 17

Receives info from cutaneous Afferents, joint afferents and muscle spindles and from here axons pass to the contralateral cerebellar Cortex via the inferior cerebellar peduncle
Wil also receive axons from the sensorimotor cortex directly and indirectly via the red nucleus

Question 18

Describe the deep pontine nuclei

Answer 18

Primary route by which the cerebral cortex communicates with the cerebellum via the basilar pons

Question 19

Describe the reticular formation

Answer 19

Regulates spinal reflexes - provides a key input to the cerebellum that relates to the manner in which reticular neurons regular extensor motor tone at any given time
Several of the nuclei within this receive input from the sensorimotor cortex serving as a relay for cerebral cortical inputs to the cerebellum

Question 20

Describe the Tectum

Answer 20

Cerebellum also receives fibres arising from the sup. And inf. colliculi of the Tectum to provide visual and auditory information respectively
Do so by projecting to the pontine nuclei, which in turn go through the ,idle cerebellar peduncle to the cerebellar cortex

Question 21

Describe the red nucleus

Answer 21

Serves as a relay from the sensorimotor cortex to the spinal cord via the rubrospinal tract
In a similar manner the sensorimotor cortex can provide signals to the cerebellar cortex via the red nucleus

Question 22

Describe the trigeminal system

Answer 22

Secondary proprioceptive fibres associated itch muscle spindle activity of the face and jaw reach the cerebellum through the mesencephalic trigeminal nucleus

Question 23

Describe the vestibular system

Answer 23

Via the ICP to the flocculonodular lobe

Question 24

What fibres does the middle cerebellar peduncle carry

Answer 24

Only afferent fibres

Question 25

Where do inputs go?

Answer 25

Deep cerebellar nuclei

Question 26

What are the deep cerebellar nuclei?

Answer 26

Separated from the cerebellar cortex by the white tater are underlying, deep, cerebellar nuclei whic are represented bi laterally. Moving laterally to medially: Dentate nucleus Emboliform Globose Fastigal (Don’t Eat Greasy Food)

Question 27

Dentate nuclei

Answer 27

Project contralaterally though the superior cerebellar peduncle to neurons in the contralateral thalamus and from thalamus to motor cortex Function: influence planning and initiation of voluntary movement

Question 28

Emboliform and Globose nuclei

Answer 28

Project mainly to the contralateral red nuclei and a small group is projected to the motor cortex Function: Red nuclei -> rubrospinal tract control of proximal limb muscles

Question 29

Fastigial nuclei

Answer 29

Project to the vestibular nuclei and to the pontine and medullary reticular formation Function: vestibulospinal and reticulospinal tracts

Question 30

Overview of cerebellar output/efferent

Answer 30

Cerebellar cortex ->deep nuclei _ ->thalamus -> cerebral cortex -> vestibular nuceli -> inferior olive -> red nucleus

Question 31

Cerebellar cytoarchitecture

Answer 31

Each folium - cortex and deep white matter (projections of Purkinje cell fibres to deep cerebellar nuclei) 3 layered cortex

Question 32

What are the 3 layers of the cortex

Answer 32

Molecular Purkinje Granule

Question 33

Describe the granular cell layer

Answer 33

Granule cells are abundant within this layer Contains 3-5 dendrites arranged in a claw like appearance Receive mossy fibre afferents. Axons travel to the molecular layer where they branch in a T junction to form the parallel fibres. Golgi cells are also found in the granular layer and their processes radiate to all other cell layers. They are inhibitory GABA-ergic interneurons and their cell body is usually located close to the Purkinje cell layer. Golgi cells synapse with granule cells and mossy fibres.

Question 34

Describe the Purkinje cell layer

Answer 34

Is one cell thick and contains the Purkinje cell The Purkinje neuron is the largest cell in the cerebellar cortex. Dendrites emerge from its neck and thick dendritic trees are directed into the molecular layer They receive excitatory input from granule cells via parallel fibres and climbing fibres. The axons of the Purkinje terminate in one of the deep cerebellar nuclei. Purkinje cells located in the vermal region project to the fastigial nucleus, Purkinje cells located in the hemispheres project to the dentate nucleus Purkinje cells located in the paravermal region project to the interposed nuclei. Purkinje cells are inhibitory

Question 35

Describe the molecular cell layer

Answer 35

contains the dendrites of Purkinje cells, parallel fibres (axons of granule cells) and two other cell types, basket and stellate cells. Basket and stellate cells are inhibitory GABA-ergic cells that synapse with Purkinje cells. Receive input from parallel and climbing fibres.

Question 36

What are mossy fibres

Answer 36

All cerebral afferents originating from all sources except the inferior olivary nuclear complex Include afferents from the spinal cord, posterior column nuclei, trigeminal system, pontine ad vestibular nuclei Synapse with Golgi cells and granule cell dendrites Are excitatory fibres that utilise glutamate as their NT

Question 37

Describe climbing fibres

Answer 37

Arise from the inf olivary nucleus and ascend thorugh the granular and Purkinje cell layers to reach the molecular layer Each individual fibre forms and excitatory synapse with one Purkinje cell This one to one relationship is key in motor learning Climbing fibres are excitatory and use aspartate as their NT

Question 38

Both mossy and climbing fibres…

Answer 38

Excite their target neurons in the cerebellar cortex but also provide excitatory collaterals to the deep cerebellar nuclei

Question 39

How does micro-cuitry work? Climbing fibres…

Answer 39

Excite the purkinje cells

Question 40

How does micro-cuitry work? Mossy fibres…

Answer 40

Excite the granule cells

Question 41

How does micro-cuitry work? Granule cells….

Answer 41

Make excitatory contact with the purkinje cells

Question 42

How does micro-cuitry work? Purkinje cells

Answer 42

Tonic inhibition on the activity of the neurons of the cerebellar nuclei -> all excitatory inputs converted to he inhibition -> removing the excitatory influence of the cerebellar inputs (erasing)

Question 43

All output from the cerebellar cortex is through the …… which is ……. Yet the output as a whole is….

Answer 43

Purkinje cell which is inhibitory to the deep cerebellar nuclei yet the output from the cerebellum as a whole is excitatory

Question 44

Climbing fibres and mossy fibres send….. which results in……

Answer 44

Send collaterals to the deep cerebellar nuclei which results in immediate activation of the cerebellar nuceli

Question 45

Activation of deep cerebellar nuclei is followed by

Answer 45

Inhibiton mediated by the Purkinje cell

Question 46

Purkinje cell activation is mediated by the action of the …

Answer 46

Golgi cells on the parallel fibres

Question 47

Excitation of the purkinje cell by the parallel fibres is …

Answer 47

Short

Question 48

When the excitation of the ……… ceases there is an increase in deep cerebellar nuclei excitation

Answer 48

Purkinje cell

Question 49

Release of inhibition known as

Answer 49

Disinhibition

Question 50

Signals transmitted to the deep cerebellar nuclei to its target neurons in the brain stem/thalamus after mossy or climbing fibres consists of….

Answer 50

Initial activation then inhibition followed by disinhibition

Question 51

This pattern of discharge becomes the

Answer 51

Coded message transmitted from the cerebellum to its distal targets