lecture 30 - motor systems: cerebellum

Question 1

what is truncal/gait ataxia?

Answer 1

• wide-based, unsteady, “drunken sailor” gait

- difficulty standing, sitting

Question 2

what is appendicular ataxia?

Answer 2

• dysmetria (improper measuring of distance in muscular acts)
• intention tremor
• dysdiqdochokinesia (difficulty preforming rapid, alternating movements)

Question 3

what is an intention tremor?

Answer 3

involuntary, rhythmic muscle contractions that occur during a purposeful, voluntary movement

Question 4

discuss the gross anatomy of the cerebellum

Answer 4

• 3 lobes: anterior, posterior and flocculonodular
• 2 fissures: primary and posterolateral
• individual gyrus are called folia
• 2 intermediate and 2 lateral lateral parts (divided by posterolateral fissure) of the 2 cerebellar hemispheres
• vermis
• superior, middle, inferior cerebellar preduncles

Question 5

describe the flocculonodular lobe of the cerebellum

Answer 5

-located at the ant. most portion of posterior lobe
(above posterolateral fissure)
-composed of nodulus & flocculus

Question 6

describe the vermis

Answer 6

the unpaired, median portion of the cerebellum that connects the two hemispheres

Question 7

what are the deep cerebellar nuclei? (from lateral to medial)

Answer 7

• dentate
• emboliform
• globose
• fastigial

Question 8

what is the interpositus nucleus?

Answer 8

some humans don’t have distinct emboliform and globose nuclie, they instead have one fused interpositus nucleus

Question 9

describe the basic cerebellar circut

Answer 9

• cerebellar inputs from the climbing and mossy fibres act on the cortex as well as the deep cerebellar and vestibular nuclei, which send the cerebellar outputs
• the cerebral cortex also has downstream inhibitory affects on the deep cerebllar/vestibular nuclei

Question 10

describe the cerebellar climbinf fibres in more detail

where do they come from and what is their role

Answer 10

• they origionate from the inferior olivary nucleus

- the help train cerebellar circuit during motor learning

Question 11

what are the cortical layers of the cerebellum from superficial to deep?

Answer 11

• molecular
• purkinje cell (output)
• granule cell
• white matter

Question 12

what is unique to the granule cells in the cerebellum

Answer 12

• they give rise to specialized axons called “parallel fibers” that ascend to the molecular layer of the cerebellar cortex that relay information to the purkinje cells
• i.e., they’re also involved in input

Question 13

what are the functions of the cerebrocerebellum?

Answer 13

motor planning and selection

Question 14

which specific areas of the cerebellum are involved in motor planning and selection?

Answer 14

lateral part of the hemispheres

Question 15

describe the motor planning and selection pathway

Answer 15

motor areas of the cerebral cortex –> pontine nuclei –> climbing/mossy fibres –> cerebellar cortex/dentate nucleus –> ventrolateral thalamus –> motor areas of the cortex/red nucleus

Question 16

what are the functions of the spinocerebellum?

Answer 16

sensory feedback control and motor coordination

Question 17

whic specific areas of the cerebellum are involved in sensory feedback control and motor coordination?

Answer 17

• intermediate part of the hemispheres (limbs)

- vermis (axial)

Question 18

describe the sensory feedback control and motor coordination pathway

Answer 18

somatosensory afferents, sc, motor cortex –> climbing/mossy fibres –> cortex/ interpositus nuclei (int part)/fastigial nuclei (vermis) –> motor cortex/red nucleus (int part)/motor cortex/vestibular nuclei/reticular formation (vermis)

Question 19

describe the pathway for spinal feedback from the lower limb

Answer 19

• via ventral spinocerebellar tract:

- ventral commissure –> superior cerebellar peduncle

Question 20

describe the pathway for afferent feedback from the lower limb

Answer 20

• via dorsal spinocerebellar tract:

- proprioceptive and cutaneous afferents –> clarke’s column –> inferior cerebellar peduncle

Question 21

describe the pathway for spinal feedback from the upper limb

Answer 21

• via rostral spinocerebellar tract: little known about this pathway
• enters through inferior and superior peduncles

Question 22

describe the pathway for afferent feedback from the upper limb

Answer 22

• via cuneocerebellar tract:
• proprioceptive and cutaneous afferents –> fasciculus cuneatus –> external cuneate nucleus –> inferior cerebellar peduncle

Question 23

describe the location of leg, arm, head and auditory/visual information in the vermis/the intermediate hemispheres from anterior to posterior

Answer 23

• ant. lobe: leg, arm, head
• stem of vermis: auditory/visual info
• post: head, arm, leg

Question 24

which tract is associated with the arms?

Answer 24

rostral spinocerebellar

Question 25

which tract is associated with the legs?

Answer 25

ventral spinocerebellar

Question 26

which peripheral afferents tract is associated with the arms?

Answer 26

cuneocerebellar

Question 27

which peripheral afferents tract is associated with the legs?

Answer 27

dorsal spinocerebellar

Question 28

what are the functions of the vestibulocerebellum?

Answer 28

- control, balance and equilibrium - vestibulo-ocular reflex - smooth pursuit eye movements

Question 29

what is the vestibulo-ocular reflex?

Answer 29

a gaze stabilizing reflex: ensures stable vision

Question 30

which areas of the cerebellum are involved in the vestibulocerebellar functions?

Answer 30

flocculonodular lobe

Question 31

describe the vestibulocerebellar pathway

Answer 31

vestibular apparatus --> climbing/mossy fibres --> cortex/vestibular nuceli --> vestibulospinal tract, medial longitudinal fasciculus

Question 32

the main cerebellar input/output pathways are related to the:

Answer 32

cerebellar peduncles

Question 33

describe the superior cerebellar peduncle pathway

Answer 33

- input: sc (ventral and rostral spinocerebellar) | - output: thalamus, red nucleus, tectum

Question 34

describe the middle cerebellar peduncle pathway

Answer 34

input: pontine nuclei

Question 35

describe the inferior cerebellar peduncle pathway

Answer 35

- input: vestibular nuclei, sc (dorsal and rostral spinocerebllar and cuneocerebellar), clinbing fibre from inferior olive - output: vestibular nuceli, reticualr formation, medial longitudinal fasciculus

Question 36

which vessels supply the cerebellum?

Answer 36

- superior cerebellar artery (top) - AICA (outside point on ant., middle on post.) - PICA (bottom, bit of vermis)

Question 37

what can occur as a result of cerebellar lesions

Answer 37

- ataxia (covered above) - eye movement abnormalities - speech difficulties (irregular rate/volume, slurred)

Question 38

list possible eye movement abnormalities w respect to cerebellar lesions

Answer 38

- ocular dysmetria (involves the constant under- or over-shooting of the eyes when attempting to focus gaze on somethin) - nystagmus (involuntary rhythmic side-to-side, up and down or circular motion of the eyes) - impaired vestibulo-ocular reflex