Cortico Bulbar, and other pathways Flashcards

1
Q

an infarction of the posterior limb of the internal capsule damages the

A

corticospinal and corticobulbar fibers, and somatosensory systems

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2
Q

damage to corticospinal tract in infarction of internal capsule causes

A

contralateral upper motor neuron syndrome

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3
Q

infarction of internal capsule and damage to somatosensory causes

A

contralateral sensation losses

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4
Q

damage to corticobulbar fibers that project to hypoglossal nucleus causes

A

contralateral deviation of the tongue during protrusion

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5
Q

damage to corticobulbar fibers projecting to the contralateral paramedian PPRF in the caudal pons causes

A

deviation of both eyes towards the lesion

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6
Q

PPRF receives

A

bilaterally equal tonic innervation

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7
Q

bilateral equal tonic innervation makes it possible to

A

look straight forward

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8
Q

if PPRF is lost the tonic innervation

A

of the other side is unopposed causing deviation of eyes towards the side of the damaged upper motor neuron

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9
Q

damage to the corticobulbar fibers innervating the facila nucleus causes

A

contralateral facial paralysis

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10
Q

the upper facial nucleus receives

A

bilateral innervation from the ventrolateral primary motor cortex

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11
Q

the lower facial nucleus receives

A

contralatera projections so in a unilateral central facial lesion the patient will still be able to wrinke the forehead

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12
Q

in a peripheral facial lesion,

A

the facial nerve itself is damaged and both upper and lower facial muscles are paralyzed

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13
Q

Red Nucleus is located in the

A

middle portion of the midbrain

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14
Q

Red nucleus receives

A

exicitatory connections from the ipsilateral motor cortex and from the contralateral cerebellar nuclei.

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15
Q

end of the rubrospinal tract

A

excitatory synapes of alpha and gamma motor neurons

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16
Q

route of the rubrospinal tract

A

axons of the red nuclear efferents decussate in the midbrain. Rubrospinal axons descend through the lateral brainstem and anterior horn of spinal cord and end on alpha and gamma motor neurons.

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17
Q

most rubrospinal fibers innervate

A

neurons of arm muscles

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18
Q

each red nucleus primarily facilitates

A

voluntary flexion of the muscles of the contralateral arm.

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19
Q

rubral influences on lower limb

A

minimal

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20
Q

start of medullary(lateral) Reticulospinal tract

A

reticular neclei in the medula which receive bilateral cortical input from corticoreticulofibers and somatosensory projections through the spinoreticular tract

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21
Q

lateral medullary Reticulo Spinal nuclei receives

A

Bilateral cortical input from the cortico reticulofibers and somatosensery projections from the spinoreticular tract

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22
Q

the spinoreticular tract is collaterals of

A

the anterolateral system

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23
Q

medullary RS tract ends on

A

interneurons that excite alpha and gamma motor neurons

24
Q

meduallary RS tract route

A

descends bilaterally through the lateral spinal cord

25
Q

most Medullary RS fibers facilitate

A

contraction of the flexor muscles of the limbs

26
Q

Pontine(medial) RS tract start

A

reticular nuclei in the pons

27
Q

Pontine RS nuclei receives

A

bilateral cortical input through corticoreticular fibers, they also receive somatosensory from spinoreticular tract.

28
Q

Pontine RS ends on the

A

interneurons that excited mainly GAMMA motor neurons

29
Q

pontine RS tract route

A

descends ipsilaterally through the medulla and VENTRAL anterior horn of spinal cord

30
Q

Pontine RS tract predominantly affect

A

gamma motor neurons of axial and limb extensor muscles

31
Q

Spinoreticular tract starts at

A

the pain and temperature receptors

32
Q

the SR tract ends on

A

the reticular nuclei in the pons and medulla

33
Q

the SR tract relays

A

sensory info(pain, temp and pressure) from one side of the body to the contralateral reticular nuclei.

34
Q

SR tract influence on pontine reticular nuclei may facilitate

A

contraction of the extensory muscles of the ipsilateral limb and tunk. (postural adjustment may place wieght on the foot not subject to potentially threatening stimuli)

35
Q

Lateral VS tract starts in

A

the lateral vestibular nucleus

36
Q

Lateral VS recieves

A

input from vestiublar organs and cerebellum

37
Q

Lateral VS ends on

A

excitatory interneurons that excite ALPHA motor neurons

38
Q

Lateral VS Route

A

axons descend ipislateral through medulla and the anterior horn of the spinal cord

39
Q

Lateral VS facilitates

A

regulation of muscular responses necessary for balance. motor nuerons of the axial and limb extensors(anti-grav muscles)

40
Q

Medial VS tract starts

A

in the medial vestibular nucleus

41
Q

Medial VS tract receives

A

input from the vestibular organs and the cerebellum

42
Q

Medial VS tract ends

A

on synapes of ALPHA motor neurons at the cervical and upper thoracic levels.

43
Q

Medial VS tract route

A

axons descend ipsilateraly into the spinal cord and run as the caudal exstension of the medial longitudinal fasciulus

44
Q

Medial VS facilitates

A

muscular contraction of the neck in close coordination with movements of the eyes. Many neurons release glycine to inhibit the alpha neurons

45
Q

when extrafusal muscles of the muscle contract

A

the muscle spindle loses tension and becomes slack

46
Q

when the muscle spindle is slack it is unable to

A

measure subsequent muscular stretch

47
Q

the gamma motor neuron typically innervates

A

the contractile ends of the intrafusal fibers that shorten the muscle spindle to ensure that spindle is always responsive to muscular stretch

48
Q

in myotatic reflex the 1a afferent excites

A

the alpha motor neurons serving the same muscle

49
Q

descending fibers of the Lateral CS tract, Rubrospinal and RS tract coactivate motor neurons during

A

voluntary movement

50
Q

the pontine or medial RS tract has a major excitatory influence on

A

the gamma motor neurons and can activate the muscle contraction by the gamma loop.

51
Q

gamma motor neurons stimulate the

A

muscle spindles and this indrectly stimulates the alpha motor neurons via the 1a fivers forming the afferent limb of the reflex arc

52
Q

Decorticate posturing

A

lesion rostral to the red nucleus impairs corticobulbar and coticospinal fibers, this causes flexion of the upper limbs and extension of the lower limbs

53
Q

Decorticate posturing and what happens to the different tracts

A

corticospinal tract- interrupted, imparied flexion corticobulbar tract- interrupted, paralysis of cranial nerves rubrospinal tract- intact flexion of arms medullary RS tract- intact, flexion of extremities pontine RS tract- intact extension of extremeties vestibulo spinal tracts- intact extension of extremeties

54
Q

Arms during decorticate posturing

A

flexor input from rubrospinal tract is still present so there is strong flexor innervation which is much greater than extensor imput of pontine reticulospinal tract

55
Q

legs during decorticateposturing

A

rubrospinal has no impact so the extensor innervation is more relevant so the limbs are extended

56
Q

Decerebrate posturing

A

lesion at or caudal to the red nucleus imparis cortico spinal, corticobulbar, rurbrospinal fibers, patent extends both upper and lower limbs

57
Q

during decerebrate posturing only medullary RS tract

A

promotes flexion which is overcome by innervation of the pontine RS and VS tracts.