Descending Pathways 2 (section 3)

Question 0

Activity of the LVST and MVST are important in support of the body against what?

Answer 0

Against Gravity

Maintenance of upright posture

Question 1

What are the two vestibulospinal tracts?

Answer 1

Lateral Vestibulospinal tract (LVST)

Medial Vestibulospinal tract (MVST)

Question 2

What is the ascending output from vestibular nuclei that aids in coordination of eye and head movements in the vestibulococular reflex

Answer 2

Medial Longitudianl fasciculus (MLF)

Question 3

What cranial nerves does the medial longitudinal fasciculus associate with

Answer 3

CN III
CN IV
CN VI

Question 4

Where do the cell bodies arise from in the Lateral vestibulospinal tract

Answer 4

Lateral vestibular nucleus (Deiter’s nucleus)

Question 5

How does the Lateral Vestibulospinal tract descend?

Answer 5

Uncrossed

Question 6

Function of Lateral Vestibulospinal tract

Answer 6

1. Facilitate extensor alpha and gamma motor neurons of the Lower Extremities
2. Flexors of the upper extremities

Question 7

What is the primary antigravity pathway?

Answer 7

Lateral vestibulospinal tract (LVST)

Question 8

Where do the cell bodies of the medial vestibulospinal tract arise from

Answer 8

Medial vestibular nucleus

Question 9

Where do fibers of the Medial Vestibulospinal tract primarily terminate?

Answer 9

in the cervical and upper thoracic levels

Question 10

Primary function of the MVST?

Answer 10

Inhibit upper extremity extensors

Facilitate Flexors

Question 11

Cell bodies in Tectospinal tract arise where?

Answer 11

The Superior Colliculus of the midbrain tectum

Question 12

Where does the Tectospinal tract run along with the medial vestibulospinal tract?

Answer 12

In the Upper Cervical spinal cord

Question 13

What tract has fibers that terminate in the upper four cervical segments of the spinal cord

Answer 13

Tectospinal tract

Question 14

Function of the Tectospinal tract

Answer 14

Mediate reflex postural movements of the head and neck in response to NOVEL visual stimuli

Question 15

T or F, Muscles are supplied by only one ventral root

Answer 15

False, Muscles are supplied by SEVERAL ventral roots

Example (biceps = C5-C6)

Question 16

Paresis

Answer 16

only one or two ventral roots are damaged

Question 17

Paralysis

Answer 17

Results if all roots innervating a particular muscle are destroyed

Question 18

Lesions above the C3 level can cause what type of problem?

Answer 18

Diaphragm can be denervated and leave the patient ventilator-dependent

Question 19

S2, S3 and S4 innervate what structures?

Answer 19

Bladder and bowel control

Question 20

Alpha motor neurons have what fiber diameter?

Answer 20

12-20 microns

Question 21

Gamma motor neurons have what fiber diameter

Answer 21

2-10 microns

Question 22

Alpha motor neurons have what conduction velocity

Answer 22

15-120 m/sec

Question 23

Gamma motor neurons conduction velocity (m/sec)

Answer 23

10-45 m/sec

Question 24

Function of alpha motor neurons

Answer 24

Innervates extrafusal skeletal muscle fibers

Question 25

Are alpha motor neurons myelinated?

Answer 25

Heavily myelinated

Question 26

Gamma motor neuron function

Answer 26

Innervates intrafusal muscle fibers of muscle spindle

Question 27

Are gamma motor neurons myelinated?

Answer 27

Yes myelinated

Question 28

Aut. pre-ganglionic B fibers diameter?

Answer 28

~ 3 microns

Question 29

Aut. Post-ganglionic C fibers diameter

Answer 29

~ 1

Question 30

Aut. Pre-ganglionic B fibers conduction velocity

Answer 30

3-15 m/sec

Question 31

Aut. Post-ganglionic C fibers

Answer 31

2 m/sec

Question 32

Function of C fibers

Answer 32

Post-ganglionic autonomic fibers

Question 33

Myelination of C fibers

Answer 33

Unmyelinated

Question 34

Function of B fibers

Answer 34

Pre-ganglionic autonomic fibers

Question 35

Myelination of B fibers

Answer 35

Lightly myelinated