Cortico Bulbar, and other pathways

Question 1

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

Answer 1

corticospinal and corticobulbar fibers, and somatosensory systems

Question 2

damage to corticospinal tract in infarction of internal capsule causes

Answer 2

contralateral upper motor neuron syndrome

Question 3

infarction of internal capsule and damage to somatosensory causes

Answer 3

contralateral sensation losses

Question 4

damage to corticobulbar fibers that project to hypoglossal nucleus causes

Answer 4

contralateral deviation of the tongue during protrusion

Question 5

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

Answer 5

deviation of both eyes towards the lesion

Question 6

PPRF receives

Answer 6

bilaterally equal tonic innervation

Question 7

bilateral equal tonic innervation makes it possible to

Answer 7

look straight forward

Question 8

if PPRF is lost the tonic innervation

Answer 8

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

Question 9

damage to the corticobulbar fibers innervating the facila nucleus causes

Answer 9

contralateral facial paralysis

Question 10

the upper facial nucleus receives

Answer 10

bilateral innervation from the ventrolateral primary motor cortex

Question 11

the lower facial nucleus receives

Answer 11

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

Question 12

in a peripheral facial lesion,

Answer 12

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

Question 13

Red Nucleus is located in the

Answer 13

middle portion of the midbrain

Question 14

Red nucleus receives

Answer 14

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

Question 15

end of the rubrospinal tract

Answer 15

excitatory synapes of alpha and gamma motor neurons

Question 16

route of the rubrospinal tract

Answer 16

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.

Question 17

most rubrospinal fibers innervate

Answer 17

neurons of arm muscles

Question 18

each red nucleus primarily facilitates

Answer 18

voluntary flexion of the muscles of the contralateral arm.

Question 19

rubral influences on lower limb

Answer 19

minimal

Question 20

start of medullary(lateral) Reticulospinal tract

Answer 20

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

Question 21

lateral medullary Reticulo Spinal nuclei receives

Answer 21

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

Question 22

the spinoreticular tract is collaterals of

Answer 22

the anterolateral system

Question 23

medullary RS tract ends on

Answer 23

interneurons that excite alpha and gamma motor neurons

Question 24

meduallary RS tract route

Answer 24

descends bilaterally through the lateral spinal cord

Question 25

most Medullary RS fibers facilitate

Answer 25

contraction of the flexor muscles of the limbs

Question 26

Pontine(medial) RS tract start

Answer 26

reticular nuclei in the pons

Question 27

Pontine RS nuclei receives

Answer 27

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

Question 28

Pontine RS ends on the

Answer 28

interneurons that excited mainly GAMMA motor neurons

Question 29

pontine RS tract route

Answer 29

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

Question 30

Pontine RS tract predominantly affect

Answer 30

gamma motor neurons of axial and limb extensor muscles

Question 31

Spinoreticular tract starts at

Answer 31

the pain and temperature receptors

Question 32

the SR tract ends on

Answer 32

the reticular nuclei in the pons and medulla

Question 33

the SR tract relays

Answer 33

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

Question 34

SR tract influence on pontine reticular nuclei may facilitate

Answer 34

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)

Question 35

Lateral VS tract starts in

Answer 35

the lateral vestibular nucleus

Question 36

Lateral VS recieves

Answer 36

input from vestiublar organs and cerebellum

Question 37

Lateral VS ends on

Answer 37

excitatory interneurons that excite ALPHA motor neurons

Question 38

Lateral VS Route

Answer 38

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

Question 39

Lateral VS facilitates

Answer 39

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

Question 40

Medial VS tract starts

Answer 40

in the medial vestibular nucleus

Question 41

Medial VS tract receives

Answer 41

input from the vestibular organs and the cerebellum

Question 42

Medial VS tract ends

Answer 42

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

Question 43

Medial VS tract route

Answer 43

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

Question 44

Medial VS facilitates

Answer 44

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

Question 45

when extrafusal muscles of the muscle contract

Answer 45

the muscle spindle loses tension and becomes slack

Question 46

when the muscle spindle is slack it is unable to

Answer 46

measure subsequent muscular stretch

Question 47

the gamma motor neuron typically innervates

Answer 47

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

Question 48

in myotatic reflex the 1a afferent excites

Answer 48

the alpha motor neurons serving the same muscle

Question 49

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

Answer 49

voluntary movement

Question 50

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

Answer 50

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

Question 51

gamma motor neurons stimulate the

Answer 51

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

Question 52

Decorticate posturing

Answer 52

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

Question 53

Decorticate posturing and what happens to the different tracts

Answer 53

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

Question 54

Arms during decorticate posturing

Answer 54

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

Question 55

legs during decorticateposturing

Answer 55

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

Question 56

Decerebrate posturing

Answer 56

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

Question 57

during decerebrate posturing only medullary RS tract

Answer 57

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