Anatomy-Cerebellum

Question 1

Afferent and efferent white matter of cerebellum

Answer 1

Arbor vitae

Question 2

What is this region?

Answer 2

Vermis

Question 3

Where do the highlighted structures connect to?

Answer 3

Superior cerebellar peduncle = midbrain. Middle cerebellar peduncle = pons. Inferior cerebellar peduncle = medulla.

Question 4

What is this structure separating?

Answer 4

It is the primary fissure that separates the anterior lobe (rostral) from the posterior lobe (ventral)

Question 5

What is this structure separating?

Answer 5

This is the horizontal fissure that separates superior and inferior aspects of the cerebellum.

Question 6

What is this structure separating?

Answer 6

This is the posterolateral fissure. It separates the vermis (nodulus and flocculus) from the rest of the posterior lobe.

Question 7

What are the subdivisions of the cerebellar cortex?

Answer 7

Vestibulocerebellum (red, vermis). Spinocerebellum (green, medial portions of anterior & posterior lobe). Pontocerebellum (teal, flanking hemispheric regions)

Question 8

Where do the fibers from “the boss of the cerebellum” course?

Answer 8

Vestibulocerebellar fibers project directly into the inferior cerebellar peduncle or to the vestibular nucleus, then on to the inferior cerebellar peduncle.

Question 9

Where do the fibers for unconscious and conscious proprioception go to enter the cerebellum?

Answer 9

Posterior Spinocerebellar tract = dorsal nucleus of clark -> ipsilateral inferior cerebellar peduncle. Cuneocerebellar tract = Accessory cuneate nucleus in medulla -> ipsilateral ICP. Anterior spinocerebellar tract = golgi tendon -> crosses AWC -> crosses at midbrain -> ipsilateral superior cerebellar peduncle

Question 10

Where do fibers from the reticular formation go to in the cerebellum?

Answer 10

Ascending spinal fibers -> Reticular formation nuclei -> Ipsilateral inferior cerebellar peduncle -> spinocerebellum

Question 11

Where do trigeminal fibers go to in the cerebellum?

Answer 11

Spinal Vth nucleus (pain, thermal, light touch) -> inferior cerebellar peduncle, principal sensory nucleus of V (2 pt. discrimination, vibration) -> middle cerebellar peduncle and mesencephalic nucleus of V (unconscious proprioception) -> superior cerebellar peduncle.

Question 12

Where does descending information from the frontal, temporal and occipital cortices?

Answer 12

Pontocerebellar fibers receive cortical information -> contralateral middle cerebellar peduncle -> contralateral pontocerebellum

Question 13

Where does information from the olivary nucleus (spinal, motor cortex and vestibular inputs) project to in the cerebellum?

Answer 13

Olivary nucleus -> Contralateral inferior cerebellar peduncle -> contralateral spinocerebellum, pontocerebellum and vestibulocerebellum

Question 14

How does the cerebellum somatotopically arrange incoming afferent information?

Answer 14

*

Question 15

How do nuclei organize throughout the gray matter of the cerebellum?

Answer 15

Note that the purkinje layer is the receptive dendritic layer and the molecular layer contains many of the synaptic connections with the purkinje layer.

Question 16

What are the different ways cerebellar afferents terminate in the cerebellar cortex?

Answer 16

Mossy fibers (all afferents except inferior olive’s, synapse on granule cell layer, then granule cell layer synapses on purkinje layer) and climbing fibers (inferior olive only, synapse directly on purkinje cells).

Question 17

What structures are located in this region?

Answer 17

Deep cerebellar nuclei: 1) Fastigial 2) Globose 3) Emboliform 4) Dentate.

Question 18

What structures depress the deep cerebellar nuclei?

Answer 18

Excited purkinje cells.

Question 19

What structures bypass the cortical circuitry to excite the deep cerebellar nuclei?

Answer 19

Afferent cerebellar fibers.

Question 20

Which afferent inputs provide the largest range of information for the purkinje cells? Which ones have the greatest influence on Purkinje cells?

Answer 20

Many mossy fibers synapse on single granule cells, thus each granule cell input to a purkinje cell is from lots of information and are used for coordination regulation. The climbing fibers synapse directly on the purkinje cell and thus have the greatest influence and are used for timing, synchronization and learning of motor activities.

Question 21

Where is the only place axons directly exit the cerebellum?

Answer 21

Nodulus & flocculus. This is the region of vestibulocerebellar output. Purkinje cells in the nodulus and flocculus send axons out the ICP that combine with all 4 vestibular nuclei on the ipsilateral side. This influences the lateral and medial vestibulospinal tracts.

Question 22

Functions of the vestibulospinal tract.

Answer 22

Righting reflex, head stabilizing, overriding vestibuloculuar reflex when trying to track moving objects.

Question 23

Efferent cerebellar pathway involved in maintenance of posture, equilibrium and generation of motor patterns in walking.

Answer 23

Vermal purkinje cells -> Fastigial nuclei -> Inferior cerebellar peduncle -> Bilateral vestibular & reticular nuclei -> Medial pathways of vestibulospinal & rubrospinal tract.

Question 24

Efferent cerebellar pathway involved in fine, fractioned movements and correction of on-going movements.

Answer 24

Paravermal pathway. Vermal purkinje cells -> Emboliform & Globose nuclei (interpose nuclei) -> contralateral superior cerebellar peduncle -> contralateral red nucleus (rubrospinal), contralateral VPL of thalamus -> primary motor cortex (corticospinal). Note that the LCST & rubrospinal tracts cross again on their way down so signaling passes down on the ipsilateral side of where the cerebellar signal originated.

Question 25

Efferent cerebellar pathway involved in planning and timing of complex

Answer 25

Pontocerebellar pathway. Vermal purkinje cells -> Dentate nucleus -> Contralateral Red nucleus & Contralateral VPL of thalamus -> Motor cortex & frontal cortex motor planning area -> Rubrospinal tract and Corticospinal tracts on the ipsilateral side from the original cerebellar signal.

Question 26

What regions of the cerebellum are supplied by what arteries?

Answer 26

Note that AICA affects the peduncles and affects pathways exiting and entering the cerebellum.

Question 27

Where would expect a cerebellar lesion to be located if patients present with ataxic gait, titubation (uncontrolled movement of the head), nystagmus or truncal ataxia (inability to maintain seated posture)?

Answer 27

Midline of the cerebellum. Note that this can happen with chronic alcoholism (specific for truncal ataxia), medulloblastomas, MS and cerebral vascular accidents.

Question 28

Where would you expect a cerebellar lesion to be located if patients present with dysmetria (depth perception problems), intention tremor, dysdiadochokinesis (agonist/ antagonist muscle coordination), appendicular ataxia (uncoordinated muscle movement), decomposition of movement or speech disturbances (cadence & fluctuation)?

Answer 28

Hemispheric region of the cerebellum, collective symptoms are called asynergia. Note that the intention tremor is specific for MS. Also note that you never get paralysis of muscles with cerebellar lesions.