Neuroanatomy Lab (Week 3)

Question 1

Folia

Answer 1

Folds created by sheet of tissue of the cerebellar cortex

Sheet is much thinner than cerebral cortex, so folds (folia) are much smaller

Question 2

Vermis

Answer 2

Midline structure of cerebellum (surrounded by cerebellar hemispheres)

Most obvious on ventral surface, where most closely resembles a worm

Question 3

Flocculus

Answer 3

On ventral aspect of cerebellum, immediately caudal to middle cerebellar peduncle and in cerebellopontine angle

Question 4

Three lobes of the cerebellum

Answer 4

Anterior lobe

Primary fissure separates anterior and posterior lobes

Posterior lobe

Posterolateral fissure separates posterior and flocculonodular lobe

Flocculonodular lobe

Question 5

Longitudinal divisions of cerebellum and their deep cerebellar nuclei

Answer 5

Vermis –> fastigial nucleus

Intermediate zone –> nucleus interpositus

Lateral hemispheres –> dentate nucleus

Question 6

Where are the deep cerebellar nuclei?

Answer 6

Embedded in the white matter beneath cerebellar cortex

Question 7

What projects to the vestibular nuclei?

Answer 7

Direct projections from:

Flocculus

Anterior lobe

Posterior lobe

Question 8

Afferents to cerebellar cortex

Answer 8

Vestibular inputs to flocculus and vermis

Spinal cord to intermediate zones and vermis

Cerebral cortex to lateral hemispheres (thru pontine nuclei), but also to intermediate zone for limb movement and vermis for trunk movements

Inferior olivary nucleus

Question 9

Function of longitudinal parts of cerebellum

Answer 9

Vermis: coordination of trunk movements and postural adjustments

Intermediate lobe: adjusting limb movements

Lateral hemispheres: planning movements and motor learning

Question 10

Peduncles connect cerebellum to which part of brainstem?

Answer 10

Inferior cerebellar peduncle (restiform body) to medulla

Middle cerebellar peduncle (brachium pontis) to pons

Superior cerebellar peduncle (brachium conjuctivum) to midbrain

Question 11

Peduncles are formed by which fibers?

Answer 11

Inferior cerebellar peduncle is fibers from spinal cord and medulla

Middle cerebellar peduncle is fibers from pons

Superior cerebellar peduncle is fibers inupt from cerebellum and outputs to red nucleus and motor regions of thalamus (from thalamus to cerebral cortex)

Question 12

Inputs to the cerebellum

Answer 12

There are many inputs to the cerebellum but 2 major sources are cerebral cortex and spinal cord, and the pathways are:

1) Corticopontine (cortex to pons) and pontocerebellar (pons to cerebellum) pathways
2) Clark’s column and spinocerebellar pathways
3) Other inputs

Question 13

Corticopontine and pontocerebellar pathways

Answer 13

Fibers from cerebral cortex (travel with corticospinal tract) terminate in the pontine nuclei of the pons –> fibers from pontine nuclei cross midline and pass thru middle cerebellar peduncle –> cerebellar cortex

Function of cerebellum associated with this pathway is taking info from the cerebral cortex and detecting differences between intended and actual movement

Question 14

Clark’s column and spinocerebellar pathways

Answer 14

Proprioceptive fibers from lower limb travel in spinal cord to Clarke’s nucleus (column of cells in dorsal horn of spinal cord in thoracic segments) –> fibers ascend to cerebellum via dorsal spinocerebellar tract –> enter cerebellum via inferior cerebellar peduncle

Proprioceptive fibers from upper limb project to lateral cuneate nucleus –> cerebellum and thalamus

Question 15

Other inputs to the cerebellum

Answer 15

Inferior olivary nucleus (climbing fibers)

Vestibular nuclei

Reticular formation

Question 16

Outputs of the cerebellum

Answer 16

Almost all output is directed to deep cerebellar nuclei (then to cerebral motor cortex via thalamus, spinal cord via red nucleus, and vestibular nuclei)

Also output directly to vestibular nuclei (in medulla)

Question 17

Circuitry of lateral cerebellar hemisphere and intermediate zone to see cerebellum regulates motor function on IPSILATERAL side

Answer 17

Two crossings allow cerebellum to have ipsilateral control of motor function

Connections of cerebellar hemisphere: [cerebral cortex –> down to pontine nuclei –> CROSS –>] cerebellar hemisphere –> up to dentate nucleus (deep cerebellar nuclei) –> CROSS –> red nucleus –> thalamus –> cerebral cortex –> down –> CROSS –> spinal cord –> muscles

Connections of cerebellar intermediate zone: [cerebral cortex –> down to pontine nuclei –> CROSS –>] cerebellar intermediate zone –> nucleus interpositus (deep cerebellar nuclei) –> CROSS –> red nucleus –> thalamus –> cerebral cortex –> down –> CROSS –> spinal cord –> muscles

Question 18

Clinical signs when flocculonodular lobe (vestibulocerebellum) damaged

Answer 18

Poblems with balance –> broad-based, staggering gait

Eye movements affected

Makes sense because afferents to flocculonodular lobe from vestibular nuclei

Question 19

Clinical signs when midline vermis and intermediate zones (spinocerebellum) damaged

Answer 19

Postural instability, general incoordination, ataxia, leg movements primarily affected

Called anterior lobe syndrome which makse sense because the anterior lobe is mainly in the middle (small!)

Makes sense because outputs to spinal cord and cerebral cortex; vermis is trunk movement/postural adjustments and intermediate zone is limb movement

Question 20

Clinical signs when lateral cerebellar hemispheres (cerebrocerebellum) damaged

Answer 20

Limb ataxia, hypotonia, intention tremor

Called neocerebellar syndrome because cerebral hemispheres were last to develop

Makes sense because cerebellar hemispheres receive input from cerebral cortex

Question 21

Inputs and outputs of vestibular nuclei

Answer 21

Vestibular part of CN VIII and cerebellum –> vestibular nuclei (in dorsolateral portion of medulla) –> spinal cord (via lateral vestibulospinal tract) and cranial nerve nuclei for eye movements (via MLF)

Vestibular system contributes to maintenance of balance and equilibrium