lecture 30 - motor systems: cerebellum Flashcards
what is truncal/gait ataxia?
- wide-based, unsteady, “drunken sailor” gait
- difficulty standing, sitting
what is appendicular ataxia?
- dysmetria (improper measuring of distance in muscular acts)
- intention tremor
- dysdiqdochokinesia (difficulty preforming rapid, alternating movements)
what is an intention tremor?
involuntary, rhythmic muscle contractions that occur during a purposeful, voluntary movement
discuss the gross anatomy of the cerebellum
- 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
describe the flocculonodular lobe of the cerebellum
-located at the ant. most portion of posterior lobe
(above posterolateral fissure)
-composed of nodulus & flocculus
describe the vermis
the unpaired, median portion of the cerebellum that connects the two hemispheres
what are the deep cerebellar nuclei? (from lateral to medial)
- dentate
- emboliform
- globose
- fastigial
what is the interpositus nucleus?
some humans don’t have distinct emboliform and globose nuclie, they instead have one fused interpositus nucleus
describe the basic cerebellar circut
- 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
describe the cerebellar climbinf fibres in more detail
where do they come from and what is their role
- they origionate from the inferior olivary nucleus
- the help train cerebellar circuit during motor learning
what are the cortical layers of the cerebellum from superficial to deep?
- molecular
- purkinje cell (output)
- granule cell
- white matter
what is unique to the granule cells in the cerebellum
- 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
what are the functions of the cerebrocerebellum?
motor planning and selection
which specific areas of the cerebellum are involved in motor planning and selection?
lateral part of the hemispheres
describe the motor planning and selection pathway
motor areas of the cerebral cortex –> pontine nuclei –> climbing/mossy fibres –> cerebellar cortex/dentate nucleus –> ventrolateral thalamus –> motor areas of the cortex/red nucleus
what are the functions of the spinocerebellum?
sensory feedback control and motor coordination
whic specific areas of the cerebellum are involved in sensory feedback control and motor coordination?
- intermediate part of the hemispheres (limbs)
- vermis (axial)
describe the sensory feedback control and motor coordination pathway
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)
describe the pathway for spinal feedback from the lower limb
- via ventral spinocerebellar tract:
- ventral commissure –> superior cerebellar peduncle
describe the pathway for afferent feedback from the lower limb
- via dorsal spinocerebellar tract:
- proprioceptive and cutaneous afferents –> clarke’s column –> inferior cerebellar peduncle
describe the pathway for spinal feedback from the upper limb
- via rostral spinocerebellar tract: little known about this pathway
- enters through inferior and superior peduncles
describe the pathway for afferent feedback from the upper limb
- via cuneocerebellar tract:
- proprioceptive and cutaneous afferents –> fasciculus cuneatus –> external cuneate nucleus –> inferior cerebellar peduncle
describe the location of leg, arm, head and auditory/visual information in the vermis/the intermediate hemispheres from anterior to posterior
- ant. lobe: leg, arm, head
- stem of vermis: auditory/visual info
- post: head, arm, leg
which tract is associated with the arms?
rostral spinocerebellar
which tract is associated with the legs?
ventral spinocerebellar
which peripheral afferents tract is associated with the arms?
cuneocerebellar
which peripheral afferents tract is associated with the legs?
dorsal spinocerebellar
what are the functions of the vestibulocerebellum?
- control, balance and equilibrium
- vestibulo-ocular reflex
- smooth pursuit eye movements
what is the vestibulo-ocular reflex?
a gaze stabilizing reflex: ensures stable vision
which areas of the cerebellum are involved in the vestibulocerebellar functions?
flocculonodular lobe
describe the vestibulocerebellar pathway
vestibular apparatus –> climbing/mossy fibres –> cortex/vestibular nuceli –> vestibulospinal tract, medial longitudinal fasciculus
the main cerebellar input/output pathways are related to the:
cerebellar peduncles
describe the superior cerebellar peduncle pathway
- input: sc (ventral and rostral spinocerebellar)
- output: thalamus, red nucleus, tectum
describe the middle cerebellar peduncle pathway
input: pontine nuclei
describe the inferior cerebellar peduncle pathway
- input: vestibular nuclei, sc (dorsal and rostral spinocerebllar and cuneocerebellar), clinbing fibre from inferior olive
- output: vestibular nuceli, reticualr formation, medial longitudinal fasciculus
which vessels supply the cerebellum?
- superior cerebellar artery (top)
- AICA (outside point on ant., middle on post.)
- PICA (bottom, bit of vermis)
what can occur as a result of cerebellar lesions
- ataxia (covered above)
- eye movement abnormalities
- speech difficulties (irregular rate/volume, slurred)
list possible eye movement abnormalities w respect to cerebellar lesions
- 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
