8. Cerebellum Flashcards
cerebellum: functions
- regulation of upper motor neuron activity
- coordinating movement
- matching actual movement w/ intended movement (by detecting and reducing motor error)
motor learning: define
the process of improving motor skills through practice, with long-lasting changes in the capability for responding.
key players: cerebellum and basal nuclei play a major role in such coordination.
where in the hierarchy of volitional motor control does the cerebellum fall?
affects upper motor neurons of the brainstem centers (basic movements and postural control)
cerebellum: location
posteriorly in the brain
inferior to the occipital lobe
dorsal to pons and medulla
what are the 2 components to the cerebellum?
- cerebellar CORTEX
- deep cerebellar nuclei
general organization of the cerebellum: (rule of 3s)
- 3 anatomic subdivisions of cerebellar cortex (sagittal plane)
- 3 anatomic lobes of cerebellar cortex in horizontal plane
- 3 functional subdivisions of the cerebellar corted
- 3 deep cerebellar nuclei
- 3 main fiber tracts (peduncles) for inputs/outputs
- 3 major clinical syndromes
3 anatomic divisions of cerebellar cortex in sagittal plane
- Midline: Vermis and nodulus
- Intermediate: Paravermal region of cerebellar hemisphere
- Lateral: Lateral region of cerebellar hemisphere & flocculus
which anatomic region of the cerebellum contains the NODULUS?
MIDLINE
(part of the vestibulocerebellum)
which anatomic region of the cerebellum contains the VERMIS?
Midline
(part of spinocerebellum)
which anatomic region of the cerebellum contains the FLOCCULUS?
intermediate
(vestibulocerebellum)
locate the VERMIS, NODULUS, and FLOCCULUS in the view from the 4th ventricle
vermis and nodulus: on midline
flocculus laterally
3 anatomic lobes of the cerebellum & locations
- floccolondular: anterior to posterolateral fissue on inferior surface
- anterior lobe: anterior to primary fissue
- posterior: between primary fissue and posterolateral fissure
which fissure separates the 2 anatomic lobes:
anterior lobe and posterior lobe
primary fissure
which fissure separates the following 2 anatomic lobes?
flocculonodular lobe & posterior lobe
posterolateral fissure
3 functional subdivisions of cerebellar cortex
- CEREBROcerebellum
- SPINOcerebellum
- VESTIBULOcerebellum
VESTIBULOcerebellum: structures
flocculolondular lobe (connects w/ vestibular system)
this includes both the flocculus and the nodulus
SPINOcerebellum: structures
vermis and intermediate zone (particularly in anterior lobe), which connects w/ the spinal cord
CEREBROcerebellum
lateral part of cerebellar hemispheres; (particularly in the posterior lobe) which connects w/ the cerebral cortex
function of the subdivision:
VESTIBULOcerebellum
regulates movements to control posture and balance, gaze, and VOR (vestibulo-ocular reflex)
function of the subdivision:
SPINOcerebellum
regulates gross limb movements & gait
function of the subdivision:
CEREBROcerebellum
regulates highly skilled movements, complex spatial and temporal sequences of movement (incl. speech, visually guided coordination of ongoing movement, motor planning)
3 deep cerebellar nuclei (DCN)
- dentate nucleus (laterally)
- interposed nuclei between
- fastigial nucleus (medially)
(DIF)
deep cerebellar nuclei: function
these nuclei are main source of outputs from the cerebellum;
receieve information/input from the cerebellar cortex
where is the dentate nucleus visible in anatomic sections?
located w/in white matter, deep to cerebellar cortex
3 main fiber tracts (PEDUNCLES) for inputs/outputs
and their location
- superior
- middle
- inferior
Found in lateral boundaries of the FOURTH VENTRICLE
fourth ventricle in relation to peduncles, pons, medulla
floor of 4th ventricle is diamond shaped depression
- found on dorsal surface of pons and medulla
- bordered by superior, middle, and inferior cerebellar peduncles (which form the roof of the 4th ventricle)
main function of the:
superior cerebellar peduncle
- connects cerebellum to midbrain
- contains mainly OUTPUT fibers
main function of the:
middle cerebellar peduncle
- connects cerebellum to pons
- contains only input fibers
main function of the:
inferior cerebellar peduncle
- connects cerebellum to spinal cord
- contains BOTH input/output fibers
inputs and input routes
(w/ middle cerebellar peduncle)
cerebral cortical areas project to pontine nuclei –> pontine nuclei axons cross the midline and ( via the middle cerebellar peduncle) enter the cerebellum
input route w/ inferior cerebellar peduncle
inferior cerebral peduncle contains *MAINLY axons from the:
- contralateral inferior olive, and
- ipsilateral spinal cord
- ipsilateral vestibular nuclei:
cell types in the cerebellar cortex and function
- granule (only excitatory cells in cerebellar cortex)
- purkinje (inhibitory; ONLY output cells of cerebellum)
2 types of input to PURKINJE cells
- (direct input) climbing fibers from inferior olive
- (indirect input via granule cell parallel fibers), mossy fibers from pontine nuclei, spinal cord, vestibular nuclei
describe direct input to PURKINJE cells
(climbing fiber input to purkinje cells)
- single climbing fiber enwraps Purkinje cell dendrites
- makes multiple excitatory synapses
- generates powerful purkinje cell activation –> evoking atypical action potential (complex spike)
describe indirect input to purkinje cells
(granule cells input to purkinje cells)
- granule cell axons ascend and bifurcate into parallel fibers
- each parallel fiber synapses only once on a purkinje cell
- synchronous firing of many parallel fibers are needed toa ctivate purkinje cell –> generating typical action potential
neuronal activity w/in cerebellar cortex:
simple spike activity (describe)
- high at rest
- incresaes w/ SENSORY INPUT and MOVEMENT
- signals info about sensory stimuli/movements
- INHIBITED during acquistion of new movements
neuronal activity w/in cerebellar cortex:
complex spike activity (describe)
- low at rest
- influences responsiveness of Purkinje cell to parallel fiber input
- appears to signal movement error
- increases during acquisition of new movements
- returns to low levels when new movement becomes coordinated
inputs of deep cerebellar nuclei (DCN)
- excitatory input from collateral branches of climbing and mossy fibers
- inhibitory input from Purkinje cells in cerebellar cortex
outputs of deep cerebellar nuclei (DCN)
DCN are the main source of outputs from the cerebellum to upper motor neurons in brainstem centers (reticular formation, superior colliculus) and in the motor cortex via the thalamus
targets of cerebellar output
(controversial)
match cerebellar cortex w/ deep cerebellar nuclei:
cerebrocerebellum
dentate nucleus
(premotor cortex/ motor planning)
match cerebellar cortex w/ deep cerebellar nuclei:
SPINOcerebellum
interposed and fastigial nuclei
(motor execution; motor cortex/brainstem)
match cerebellar cortex w/ deep cerebellar nuclei:
VESTIBULOcerebellum
vestibular nuclei
(balance and vestibuloocular regulation/ lower motor neurons in spinal cord and brainstem)
all pathways leaving cerebellum project to… where?
upper motor neurons
which lobe is responsible for the following functions:
- learning and coordination of complex, skilled movements
- extensive reciprocal connections w/ cerebral cortex
posterior lobe
input/output, and path of posterior lobe
- INPUTS: corticopontine input to cerebellum from MIDDLE CEREBRAL PEDUNCLE
- OUTPUT: projects to dentate nucleus, whose axons exit cerebellum via superior peduncle to motor thalamus –> motor thalamus projects to motor cortex (mainly to premotor cortex for control of motor planning)
which lobe has the following functions?
- coordination of limb movements (particularly of lower extremity)
- extensive reciprocal connections w/ spinal cord
anterior lobe
inputs/output pathway of anterior lobe
- INPUTS: from mechanoreceptors and proprioceptors
- OUTPUTS: projects to fastigial and interposed nuclei –> whose axons exit cerebellum via SUPERIOR and INFERIOR cerebellar peduncles –> project to motor thalamus –> projects to motor cortex (mainly to motor cortex for control of motor execution)
CC: posterior lobe syndrome
- ATAXIA - loos of coordination of voluntary movements
- HYPOTONIA - dec muscle tone
- DYSMETRIA - inability to control ROM
- DYSDIADOCHOKINESIA - inability to perform rapid alternating movements
- TREMOR - intension tremor from disruption of normal agonist/antagonist contractions
- Disrupted or explosive speech
CC: anterior lobe syndrome
- ATAXIA - loss of coordination of voluntary movements, mainly of lower limbs
- HYPOTONIA - dec. muscle tone
- GAIT INSTABILITY
Which lobe is responsible for the following functions:
- coordination of axial (paraxial) muscles, movements involved in maintaining upright stance and balance, and eye movements to maintain direction of gaze
- reciprocal connections w/ vestibular nuclei
flocculonodular lobe
inputs/outputs of flocculonodular lobe
- INPUTS: direct input from vestibular apparatus
- OUTPUTS: projects to fastigial and vestibular nuclei –> vestibular axons project to spinal cord and to cranial nerve nuclei controlling extraocular muscles
CC: Floculonodular lobe syndrome
- INABILITY TO MAINTAIN BALANCE
- ATAXIA - loss of coordination of movements in axial muscles (truncal ataxia)
- GAIT INSTABILITY
