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19 Cards in this Set

  • Front
  • Back
basal ganglia output
from globus pallidus internus and substantia nigra
modulation of basal ganglia output
GPi/SNr send fibers to VL/VA and to mibrain tegmentum PPTg for modulation of reticular activity
where does VA and VL areas of thalamus project in the cerebral cortex
VA projects to pre-motor cortex (area 6)
VL projects to primary motor cortex (area 4)
area 6 provides the "GO" signal
Cortico-rubrospinal tract
Originates from cortex (mainly from the motor cortex--area 4 and 6)
Descends IPSILATERALLY in the internal capsule
Terminate on red nucleus
Neurons in red nucleus CROSS midline and form rubrospinal tract
Tract descends to spinal cord and terminate on alpha neurons
Pathway is biased
Alpha flexorsà excitatory
Alpha extensorsà inhibitory
Involved in rthymic movements like swing arms when walking
Corticoreticular fibers
Has nothing to do w/ movements
Act on postural involuntary reflexes; maintains muscle tone
Originates IPSILATERAL cerebral hemisphereà descends BILATERALLY to reticular core
Terminate mainly in reticular nucleus (medial 2/3) of medulla and pons
Reticular nucleus then give rise to lateral (medullary) reticulospinal tractà from medulla
Reticular nucleus then give rise to anterior (pontine) reticulospinal tractà from pons
Both tract descends to spinal cord and act mostly on gamma extensors
ARST excites gamma extensors
LRST inhibits gamma extensors
Both tracts has central autonomic fibers for control of visceral functions
Cerebellar modulation of motor centers
correction of movement via
cortico-ponto-cerebellar system
cortico-rubro-olivo-cerebellar system
input to cerebellum
Orginates from frontal, parietal, temporal and occipital cortices
Frontopontine fibers pass in IPSILATERAL anterior limb of internal capsule, occupy media 1/5 of crus cerebri, terminate in basilar pontine gray
Parieto/temporo/occipito-pontine fibers pass in IPSILATERAL posterior limb of internal capsule; occupy lateral 1/5 of crus cerebri, terminate in basilar pontine gray
From pontine gray, fibers CROSS MIDLINE, follows middle cerebellar peduncle, terminate in CONTRALATERAL cerebellar cortex and deep cerebellar nuclei
Function: correction of movements generated by the cerebral cortex by the cerebellum
cortico-rubro-olivo-cerebellar system
"input to cerebellum"
Fibers from frontal cortexà terminates in IPSILATERAL red nucleusà fibers from red nucleus (TEGMENTAL TRACT) goes to IPSILATERAL inferior olivary nucleusà fibers from inferior olivary nucleus send axons to CONTRALATERAL cerebellum via inferior cerebellar peduncle
Olivocerebellar fibers terminate as climbing fibers in all areas of CONTRALATERAL cerebellar cortex and deep cerebellar nuclei
function of cortico-ponto-cerebellar fibers
planning, initiation adn maintenance of discrete, skilled motor activity
function of cortico-olivo-cerbellar
associated motor activity; associated w/ circuitry of basal ganglia
cerebellar "output" system to motor centers
Dentato-rubro-thalamic system
Cerebellar "output" (feedback)
Major output
Arises from lateral three deep cerebellar nuclei (dentate, emboliform, globose)
Fibers leave cerebellum by superior cerebellar peduncle; CROSS the midline in caudal midbrain, ascend to upper midbrain and thalamic levels, terminates in red nucleus (mostly fibers from globose and emboliform) and in VL of thalamus (mostly from dentate)
Excitatory to red nucleus and VL thalamus
Cerebello-vestibulo-reticulo-spinal system
cerebellar "output"
Arises from medial parts of cerebellar cortex, flocculo-nodular lobe, and fastigial nuclei
Fibers go to vestibular nuclei or to medial reticular core of medulla and ponsà both send fibers to descending pathways via vestibulospinal and reticulospinal tracts
Modulates postural reflexes and muscle tone; antigravity muscles
function of rubrospinal tract
facilitates alpha flexors and inhibit alpha extensors
mediates the swing phase of walking--rhythmic movements
function of lateral and anterior reticulospinal tracts
lateral--inhibits gamma extensors
anterior--excites gamma extensors
function of tectospinal fibers and MLF
inhibit gamma extensors of neck and upper back muscles
function of vestibulo-spinal fibers
facilitate alpha extensors
function of cortiospinal fibers
faciliate and inhibit both flexors and extensors, but it biased
faciliation is towards flexors of upper limb and extensors of lower limb
Decerebrate rigidity
Cortico-reticular fibers inhibit anterior reticulospinal tract which facilitates gamma extensors; so lesion to cortico-reticular fibers will “disinhibit” ARST and results in hyperextension
Cortico-reticular fibers also activates lateral reticulospinal tract which inhibit gamma extensors; so lesion to cortico-reticular fibers will also result in hyperexention