Neuroscience

Front 1

basal ganglia output

Back 1

from globus pallidus internus and substantia nigra

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modulation of basal ganglia output

Back 2

GPi/SNr send fibers to VL/VA and to mibrain tegmentum PPTg for modulation of reticular activity

Front 3

where does VA and VL areas of thalamus project in the cerebral cortex

Back 3

VA projects to pre-motor cortex (area 6)
VL projects to primary motor cortex (area 4)
area 6 provides the "GO" signal

Front 4

Cortico-rubrospinal tract

Back 4

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

Front 5

Corticoreticular fibers

Back 5

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

Front 6

Cerebellar modulation of motor centers

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correction of movement via
cortico-ponto-cerebellar system
cortico-rubro-olivo-cerebellar system

Front 7

CORTICO-PONTO-CEREBELLAR SYSTEM
input to cerebellum

Back 7

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

Front 8

cortico-rubro-olivo-cerebellar system
"input to cerebellum"

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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

Front 9

function of cortico-ponto-cerebellar fibers

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planning, initiation adn maintenance of discrete, skilled motor activity

Front 10

function of cortico-olivo-cerbellar

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associated motor activity; associated w/ circuitry of basal ganglia

Front 11

cerebellar "output" system to motor centers

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dentato-rubro-thalamic
cerebello-vestibulo-reticulo-spinal

Front 12

Dentato-rubro-thalamic system
Cerebellar "output" (feedback)

Back 12

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

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Cerebello-vestibulo-reticulo-spinal system
cerebellar "output"

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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

Front 14

function of rubrospinal tract

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facilitates alpha flexors and inhibit alpha extensors
mediates the swing phase of walking--rhythmic movements

Front 15

function of lateral and anterior reticulospinal tracts

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antagonists
lateral--inhibits gamma extensors
anterior--excites gamma extensors

Front 16

function of tectospinal fibers and MLF

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inhibit gamma extensors of neck and upper back muscles

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function of vestibulo-spinal fibers

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facilitate alpha extensors

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function of cortiospinal fibers

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faciliate and inhibit both flexors and extensors, but it biased
faciliation is towards flexors of upper limb and extensors of lower limb

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Decerebrate rigidity

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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