Lab 7 Structures

Question 1

what are the 2 spinal cord targets of the ventral gray matter?

Answer 1

• lateral motorneurons (MNs) and interneurons (INs)
• medial motorneurons (MNs) and interneurons (INs)

Question 2

where do dorsolateral spinal cord pathways terminate? movement type?

Answer 2

• terminate/synapse on lateral MNs and INs
• serving single limb movements

Question 3

where do ventromedial spinal cord pathways terminate? movement type?

Answer 3

• terminate/synapse on medial MNs and INs
• serving axial/proximal limb girdle muscles
• info shared with medial MNs/INs on one side is shared with opposite side

Question 4

what is the function of the lateral corticospinal tract?

Answer 4

• serves limb muscles
• enables fractionation of movement (fine motor control/coordinated movement) of fingers, hands, UE
• modulate sensory info

Question 5

origin of 1st neuron

CST

Answer 5

• precentral gyrus (motor/premotor: 60%)
• postcentral gyrus: 40%

Question 6

projections of 1st neuron

CST

Answer 6

cerebral white matter, internal capsule, cerebral peduncles through ventral pons/medulla as “pyramids”

Question 7

crossing of 1st neuron

CST

Answer 7

pyramidal decussation of lower medulla (90% of fibers cross to become lateral CST in spinal cord)

Question 8

termination of 1st neuron

CST

Answer 8

• lateral MN/IN of ventral horn of spinal cord
• some to dorsal horn neurons/intermediate gray
• connects to outgoing alpha motor neuron

Question 9

where do the ventral corticospinal tract fibers come from?

Answer 9

10% of lateral corticospinal tract fibers that do not cross at pyramidal decussation but stay ipsilateral

Question 10

where does ventral corticospinal tract synapse?

Answer 10

medial MNs and INs (shares info with MN/IN on contralateral side)

uncrossed

Question 11

what does ventral corticospinal tract serve?

Answer 11

serves bilateral axial/trunk muscles

Question 12

what is the function of the rubrospinal tract?

Answer 12

• facilitate MN that innervate large mucle movements/fine motor control of UE
• primarily serves cervical regions (greater influence on flexor muscles/inhibits extensors muscles)

Question 13

where does red nucleus receive major input from?

Answer 13

primary/premotor areas

Question 14

origin of 1st neuron

RuST

Answer 14

arises from Red nucleus located in midbrain

Question 15

projections of 1st neuron

RuST

Answer 15

passes through contralateral midbrain, pons, medulla on its way to cervical levels of spinal cord

Question 16

crossing of 1st neuron

RuST

Answer 16

fibers cross immediately upon exiting Red nucleus

Question 17

termination of 1st neuron

RuST

Answer 17

terminates on lateral MNs/INs of ventral horn at primarily cervical spinal levels

Question 18

what is the function of the vestibulospinal tract?

Answer 18

convey impulses from labyrinth

Question 19

how many/what are the tracts that comprise vestibulospinal tract?

Answer 19

• medial
• lateral

Question 20

what is the function of the medial vestibulospinal tract?

Answer 20

• activates LMN associated with spinal accessory nerve
• rotating/lifting of head and shoulder blade
• movements appropriate for orientation of individual during altered posture/balance

Question 21

origin of 1st neuron

medial VST

Answer 21

medial vestibular nucleus

Question 22

projections of 1st neuron

medial VST

Answer 22

exits medial vestibular nucleus and descends in white matter pathway → medial longitduinal fasciculus (MLF)

Question 23

crossing of 1st neuron

medial VST

Answer 23

primary tract does NOT cross

Question 24

termination of 1st neuron

medial VST

Answer 24

terminates on ipsilateral medial MN/IN of ventral horn primarily at cervical levels

Question 25

what is the function of the lateral vestibulospinal tract?

Answer 25

* important for maintenance of upright posture/balance via excitation of antigravity/extensor muscles * mainly of trunk/ipsilateral limb girdle muscles

Question 26

origin of 1st neuron | lateral VST

Answer 26

lateral vestibular nucleus

Question 27

projections of 1st neuron | lateral VST

Answer 27

exits nucleus/descends in white matter pathway

Question 28

crossing of 1st neuron | lateral VST

Answer 28

primary tract does NOT cross

Question 29

termination of 1st neuron | lateral VST

Answer 29

terminates on ipsilateral medial MN/IN of ventral horn primarily at all spinal levels

Question 30

what is the function of the reticulospinal tract?

Answer 30

* coordinates trunk/proximal muscle response during limb movement via balancing actions between extensors and flexors * lateral RST → role in suppressing extensor activity * medial RST → role in facilitating extensor activity

Question 31

what are propriospinal tracts?

Answer 31

* interneurons forming white matter pathway surrounding perimeter of ventral horn * relay/shares info across a few (short) or many (long) spinal segments * cell body in 1 spinal segment and axon terminating in another spinal segment

Question 32

what is the function of short propriospinal tract neurons?

Answer 32

* connect neighboring segments * travel dorsolaterally * tend to communicate between lateral motor neurons (info from descending LCST and RuST)

Question 33

what is the function of long propriospinal tract neurons?

Answer 33

* travel longer distances to remote spinal segments * travel ventromedially * tend to communicate between medial motor neurons (info from VST, RST-like)

Question 34

what is the corticobulbar tract?

Answer 34

collectively refers to any descending CN related motor axons from cerebral cortex traveling to respective contralateral nuclei which in turn gives rise to respective cranial nerves

Question 35

path of corticobulbar tract

Answer 35

lateral aspect of motor cortex (precentral gyrus) and association areas → CN nuclei of contralateral brainstem

Question 36

what is the function of the motor component of the descending trigeminal pathway?

Answer 36

smaller component of trigeminothalamic tract which innervates skeletal muscle (muscles of mastication)

Question 37

what is the path of the descending motor trigeminal pathway?

Answer 37

motor fibers from motor nucleus of V → foramen ovale → skull → supply muscles of mastication

Question 38

label descending pathways

Answer 38