cerebellum

Question 1

primary fissure

Answer 1

gives the anterior and posterior fissures.

Question 2

The posterolateral fissure gives

Answer 2

the posterior and flucondular

Question 3

Vermis

Answer 3

controls proximal and axial trunk tone.

Question 4

Intermediate portion

Answer 4

control

Question 5

Lateral portion

Answer 5

controls the distal muscles and motor planning.

Question 6

Deep cerebellar nuclei

Answer 6

Dentat- largest
Emboliform
globus
fastigial

Dentate receives input from the vermis.
Emboliform and globus- intermediate

Question 7

Microscopic circuit of the cerebellum.

Answer 7

Major input:
climbing fibers and mossy fibers.
Mossy fibers arise from everywhere.
The mossy fibers send excitatory axons to the granule cell layer that send axons of parallel fibers that synapse with the purkinjie fibers as they ascend.

The climbing fibers arise from the contralateral olivary nucleus. one climbing fiber synapse with 10 prukinjie fibers but each pruknjie is excited by one climbing fibers.
They have a modulatory effect on purknjie to reduce the response from the parallel fibers.
Interneurons- basket and stellat.
Basket and stellate are located in the molecular layer.
They modulate by feedback inhibition to increase roselution in time and space.

Question 8

Summary of the cerebellar microcircuit

Answer 8

All cells going up are excitatory: 
1- mossy fibers. 
2- Climbing fibers. 
3- parallel fibers. 
The mossy fiber excites the granule layer that excites the inhibitory purkinie fibers. 

The Climbing fibers excites the inhibitory purknjie fibers directly,

All cells going down are inhibitory: 
1- stallets. 
2- Golgi. 
3- basket. 
4- purknjie fibers.

Question 9

Major outputs of the cerebellum

Answer 9

1- lateral cerebellum- goes to the dentate nucleus –> superior cerebellar peduncle –> to the thalamic fasciulus to the VL then motor and pre-motor cortex.
Few fibers pass to the parvocellular red nucleus then to the infrerior oliver as the central tegmental tract.
2- The intermediate –> interposed nuclei –> superior cerebellar peduncle –> thalamic fasiculus–> to VL and motor –> lateral corticospinal tract.
Few fibers go to magnocellular of red nucleus .
3- Vermis and fluconodular –> superior cerebellar peduncle –> or juxtrarestiform body –> VL–> motor cortex to the anterior corticopspinal tract,.

Question 10

Purkinjie cells

Climbing fibers.

Inhibitor interneurons

Golgi cells

Answer 10

They are the major output to the cerebellum.
They give an inhibitory output to the deep cerebellar nucle

• arise from the contra-lateral inferior olivary complex. They form excitatory synapses.
• Climibing fibers have a stronge modulatory effect on purknjie cells.
• Basket and stellate cells located in the molecular layer and inhibit the purkinjie dendrites and the cell bodies,
• They are located in the granule cell layer. They are excited by parallel fibers in the molecular layer that causes feedback inhibition on the activation of granular cells.

Question 11

excitatory pathways summary

Answer 11

1- Mossy fibers- granules- purkinjie.
2- Climbing fibers- purkinjie fibers.

Mossy fibers, climbing fibers, granule cells are excitatory
Basket, stellate and Golgi cells, purkinjie are all inhibitory

Question 12

cerebellar output pathways.
Lateral- goes to dentate

Intermediate cerebellum- gloobus and the emboliform- interposed. It controls the ongoing movement activities.

Cerebellar vermis controls the proximal and trunk muscles- it projects to the fastigial nucleus.

Fluconodular : vestibule-ocular reflex .

Answer 12

Main output is through the purkijie cells.
The purkinjie will go to the dentate nucleus then to superior cerebellar peduncle then to VL of the thalamus then thalamic fasiculus then to the premotor, motor cortex. The lateral cerebellum goes to the dentate nucleus.
The emboliform, gloobos- to the superior cerebellar peduncle to the VL thalamus then to the lateral corticospinal system.
Fibers from the red nucleus go to the caudal part( magnocellular) which also controls the ruprospinal tract- lateral motor system control.

The output is through partially superior cerebellar peduncle and juxtrarestiform and the unicinate fasciculus- it influence the medial motor system.

The vermis- fastigial nucleus: through superior cerebellar peduncle to the VL to the anterior corticospinal tract.

The vermis fastigial through the juxtrarestiform body to the reticulospinal, and the vestibulospinal pathways.

Question 13

Red nucleus

Answer 13

Has two parts - rostral which is the parvocellular.

The magnocellular which is caudal part- gives the ruprospinal tract.

Question 14

Cerebellar input - main fibers are mossy and climbing fibers.

Answer 14

Cortex input: from frontal/parietal/ temporal and occipital to the corticopontine to the pontine nuclei to the cerebellopontine through the MIDDLE cerebellar peduncle then to the mossy fibers and the rest of the cerebellum.

Second input is SPINOCEREBELLAR:
dorsal spinocerebellar and ventral spinocerebellar
Cuneucerebellar and rostral spinocerebellar.

The ongoing movement of upper and lower extremities are provided by cuneocerebellar and dorsal spinocerebellar tracts.
The advantage is to improve the ongoing movements.
1- the dorsal spinocerebellar- to the gracile funculus, few of the fibers will ascend in the inferior cerebellar peduncle giving mossy fibers to the cerebellar peduncle.
few of the fibers terminate in the nucleus caudalis of clarks that is located in the interemediate zone of the spinal cord from C8 to L2,3.

Cuneocerebellar- provides feedback to the ongoing movement of the upper extremities. they are located in the cuntenus fasiculus that synapse on the external cuneate nucleus in the medulla.

Question 15

Floconudular lobe lesions

Answer 15

can cause saccadic intrusions.
Can cause loss of suppression of the VOR.
Nystagmus that changes direction based on the gaze.