Cerebellum Flashcards
what is the function of the cerebellum?
regulation (improving/correcting) of motor control via upper motor neurons.
Describe the peduncles in terms of input/output from the cerebellum:
superior peduncle provides output to midbrain
middle cerebellar peduncle provides input via pons
inferior provides input and output via medulla and brainstem
fibers from the superior peduncle terminate in which regions:
contralateral red nucleus and thalamus
the primary fissure separates:
anterior and posterior lobes of the cerebellum
the posterolateral fissure separates
the posterior & flocculonodular lobes
What is the significance of the cerebellar tonsil?
lies superior to the foramen magnum; w/ increased intracranial pressure, may herniate down and compress respiratory centers in medulla & spinal cord
describe the role of the flocculonodular lobe:
vestibulocerebellum/archicerebellum: balance, regulation of eye movement, role in VOR
describe the location, divisions and role of the spinocerebellum:
vermis + intermediate areas just lateral to vermis. Role in coordinating muscle tone of axial (vermis) and limbs (intermediate area). input from spinal cord.
describe the input and role of the cerebrocerebellum:
neocerebellum/pontocerebellum: input from contralateral pontine nuclei. Planning and initiating skilled movement + learning of movement
the deep cerebellar nuclei in the white matter of the cerebellum are, from medial to lateral:
fastigial, interposed, dentate
the three layers of the cerebellar cortex are:
molecular, purkinje fibers, granular (out to in)
there are __ types of neurons in the cerebellar cortex. They use ____ as a neurotransmitter. All except ___ are inhibitory. The ___ cell is the only output from the cortex. The most abundant type is ____ with long axons called ___ ____
5;
GABA; granule are excitatory;
Purkinji = output. Abundant = Granule; parallel fibers.
Describe the relationship of the granule cells with purkinje cells:
where do purkinji fibers terminate?
granule cells have long axons that are collectively called parallel fibers. Many parallel fibers synapse on the dendrites of purkinje fibers in the molecular layer of the cerebellar cortex. purkinji fibers synapse in deep cerebellar nuclei (+ some to vestibulocerebellum to vestibular complex)
describe mossy fibers:
one of major inputs to cerebellum. Coming from cerebrum via pons, spinal tracts etc. One mossy fiber contacts thousands of granule cells in the granular layer of the cortex. Excitatory.
what is the course of the climbing fibers? what is their role?
extend from inferior olivary nucleus through inferior peduncle to contact purkinji fibers. ~ 1:1 ratio = highly specific. One of two major sources of input to cerebellar cortex. excitatory. Role is in plasticity - if active at same time as granule cells, those synapses will be diminished.
the entire output of the cerebellar cortex is ____
inhibitory
climbing fibers are activated when:
the outcome is:
expectations for the outcome of a movement or motor action are not met = message of error
outcome: every purkinji fiber synapse w/granule cells activated when climbing fiber is activated will be weakened
contrast short and long term modification of synapses:
short term: phosphorylation of AMPA receptors
long term: internalization of AMPA receptors
describe the input to the vestibulocerebellum/flocculonodular lobe:
from maculae and cristae in ears via vestibular nerve of CNVIII, and complex, via ipsilateral inferior peduncle.
spinocerebellar input:
input = from spinocerebellar tracts monitoring muscle tone/stretch (cuneo from arms external cuneate nucleus, dorsal from legs, Clarke's nucleus) + visual information. enters via inferior peduncle output = reg muscle tone and adjustment of movement.
somatotopic organization of spinocerebellum:
vermis = trunk
intermediate areas = limbs
spinocerebellar output from vermis:
vermis > fastigial nuclei >
- vestibular nuclei & reticular formation > reticulospinal tracts for control of axial muscles inc head/neck &
- Thalamus > motor cortex to control facial muscles/tongue
describe spinocerebellar output from intermediate areas:
spinocerebellum controls ____ (ipsi/contrlateral) side of body:
intermediate area > interposed nuclei > superior cerebellar peduncle > decussate in caudal midbrain >
1. VL of thalamus > corticospinal tracts > control limb muscles
2. contralateral red nucleus > rubrospinal tract (decussates again )
double-crossing = Controls ipsilateral side of body
Cerebrocerebellum function:
fine-tuning of highly skilled, voluntary movement; planning and initiating of movement
input to the cerebrocerebellum is via:
cerebral cortex > pontine nucleus > middle cerebral peduncle
output from cerebrocerebellum:
> dentate nucleus > superior cerebellar peduncle >
1. VL of thalamus > motor and pre-motor cortices (via dentatothalamic fibers)
& 2. parvocellular region of Red nucleus via dentatorubral fibers > inferior olivary nucleus > climbing fibers to cerebellar cortex
what is the triangle of Molleret:
connection from dentate nucleus to superior cerebellar peduncle to inferior olivary nucleus and back to cerebral cortex. damage > incoordination
