development of the nervous system: cellular & molecular...
TRANSCRIPT
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Cerebellum
Steven McLoon
Department of Neuroscience
University of Minnesota
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Friday’s lecture is by
the other Dr. McLoon!
Please attend the lecture live if you can!
Course News
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• The cerebellum has approximately half of all the neurons in the central
nervous system.
• The cerebellum receives information from all sensory and motor systems.
Anatomy of the Cerebellum
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Anatomy of the Cerebellum
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• Three anatomical lobes based on fissures:
• Anterior lobe
• Posterior lobe
• Flocculonodular lobe
Anatomy of the Cerebellum
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• Two vertical grooves divide the cerebellum
into the vermis and two hemispheres.
Anatomy of the Cerebellum
vermis
hemisphere
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• The cerebellar cortex has a series of folia that run
from side to side (similar to gyri of the cerebral cortex).
Anatomy of the Cerebellum
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Ventral surface of the cerebellum
• Superior, middle and inferior cerebellar peduncles attach the cerebellum
to the midbrain, pons and medulla respectively on both sides; they are
the only routes for axons into and out of the cerebellum.
Anatomy of the Cerebellum
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• Cerebellum has two cell groups:
• Cerebellar cortex
• Deep cerebellar nuclei
Anatomy of the Cerebellum
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• Three pairs of cerebellar nuclei:
• Fastigial nucleus (medial)
• Interposed nuclei
• Dentate nucleus (lateral)
• The main output of the
cerebellum is via the deep
cerebellar nuclei.
Anatomy of the Cerebellum
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Neuro-Circuitry of the Cerebellum
• The circuitry of cerebellar cortex is
remarkably the same across the entire
cerebellum.
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• The neurons include granule cells that
synapse with Purkinje cells via parallel
fibers (granule cell axons) that run
parallel with the folia.
Neuro-Circuitry of the Cerebellum
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• The cerebellar cortex has a series of folia that run
from side to side (similar to gyri of cerebral cortex).
Anatomy of the Cerebellum
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• The neurons include granule cells that
synapse with Purkinje cells via parallel
fibers (granule cell axons) that run
parallel with the folia.
Neuro-Circuitry of the Cerebellum
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• The dendritic tree of each Purkinje
cells is in a single flat plane
perpendicular to the long axis of the
folia.
Neuro-Circuitry of the Cerebellum
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• Cerebellum has two inputs:
• Mossy fibers from many parts of the
CNS to the granule cells..
Neuro-Circuitry of the Cerebellum
• Climbing fibers from
the inferior olivary
nucleus to the
Purkinje cells.
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climbing fiber
Purkinje cell
Neuro-Circuitry of the Cerebellum
• Each Purkinje cell receives input from a single climbing fiber and from
thousands of granule cell axons.
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• Inferior olivary nucleus is in the
upper medulla.
ventral dorsal
dorsal
ventral
Neuro-Circuitry of the Cerebellum
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• The inferior olivary nucleus
participates in a feedback loop with
cerebellum and red nucleus.
Neuro-Circuitry of the Cerebellum
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• Purkinje cells are the output of the
cerebellar cortex, and they send their
axons to the deep cerebellar nuclei.
Neuro-Circuitry of the Cerebellum
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• Other types of interneurons integrate
across folia.
Neuro-Circuitry of the Cerebellum
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Function of the Cerebellum
• Cerebellum has three main functional domains:
• Spinocerebellum (blue)
• Cerebrocerebellum (brown)
• Vestibulocerebellum (red)
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Function of the Cerebellum
Spinocerebellum:
• Main input is from spinocerebellar tracts
& tracts from cranial nerve sensory
nuclei, which carry proprioceptive
information.
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Function of the Cerebellum
Spinocerebellum:
• The input is somatotopically organized.
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Function of the Cerebellum
Spinocerebellum:
• Processed in vermis & intermediate
hemispheres of cerebellar cortex.
• Output is to interposed nuclei; then to
the red nucleus.
• Red nucleus projects to spinal cord &
cranial nerve nuclei via rubrospinal tract.
• Coordinates movements; makes mid-
course corrections; maintains posture
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Ian Waterman, at age 19, had a virus that
destroyed his proprioceptive system.
Immediately after his illness, he was unable to
walk or do most any motor task.
He learned to walk and do other motor tasks
using only vision to monitor a movement.
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Cerebrocerebellum:
• Main input is from cerebral cortex via
the pontine nuclei.
• Pontine nuclei send axons to the
contralateral side of the cerebellum
via the middle cerebellar peduncle.
Function of the Cerebellum
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Function of the Cerebellum
Cerebrocerebellum:
• Processed in lateral hemispheres.
• Output is to dentate nucleus; then to
ventrolateral nucleus of the thalamus;
then to cortex.
• Coordinates movement planning and
learned movements.
Also involved in cognitive functions.
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Function of the Cerebellum
Vestibulocerebellum:
• Main input is from vestibular nuclei and
vestibular nerve.
• Processed in flocculonodular lobe.
• Output is to the fastigial nucleus and
directly to vestibular nuclei.
• Vestibular nuclei send axons to spinal
cord & cranial nerve motor nuclei.
• Maintains balance and coordinates
head & eye movements.
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Function of the Cerebellum
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Function of the Cerebellum
Important functions of the cerebellum:
• Movement synergy (coordinate multiple muscles and muscle groups)
• Maintain appropriate muscle tension and speed of movement
• Maintain balance and posture (largely through extensor muscles)
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Three common symptoms of cerebellar pathology:
• Ataxia – inaccuracy in speed, force and distance of movements (i.e.
uncoordinated); often under or over reach for an object; staggering and
lurching walk
• Tremor – involuntary movement most pronounced when trying to perform
an accurate movement
• Nystagmus – rapid involuntary movements of the eyes
Cerebellar Pathology
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Cerebellar Pathology
• Cerebellar problems are typically due to strokes, tumors or a neuro-
degenerative disease (often genetically based).
• Unilateral cerebellar pathology results mainly in ipsilateral motor
problems.