Efferent Motor Pathways - Upper Motor Neurons (10B)

Question 0

Which Brodmann area is associated with the primary motor cortex? What is the name of the large motor neurons found there?

Answer 0

Brodmann area #4 - contains Betz cells

Question 1

Where do upper motor neuron cell bodies originate?

Answer 1

In the precentral gyrus (primary motor cortex)

Question 2

What Brodmann area is associated with both the promotor area and the supplementary motor area?

Answer 2

Brodmann area #6

Question 3

What Brodmann areas are associated with the primary somatosensory cortex?

Answer 3

Areas 3, 1, 2

Question 4

What 2 Brodmann areas are associated with the parietal association cortex?

Answer 4

5 and 7

Question 5

Beginning at the the genu of the internal capsule and moving posteriorly, what is the order of the structures innervated, regarding the somatotropin organization of the corticospinal fibers?

Answer 5

Arm, trunk, leg

*corticobulbar fibers are located nearest the genu

Question 6

In the brainstem, what structure so the corticospinal and corticobulbar structures travel as?

Answer 6

Cerebral peduncle

Question 7

In the cerebral peduncle, where are the fibers headed to lower limbs located? Upper limbs?

Answer 7

Lower limbs = most dorsal-lateral

Upper limbs = most ventral-medial

Question 8

Do corticospinal fibers serving the limbs or trunk travel on the contralateral side once in the cervical spine?

Answer 8

Limbs - these fibers cross over at the pyramids and travel as the lateral tract; those serving axial muscles are found in the anterior (ventral) tract, which doesn’t crossover ver until reaching the spinal level they will leave the cord via ventral root

Question 9

In the lateral corticospinal tract are fibers serving lower limb lateral or medial?

Answer 9

Lateral (same as in posterior limb of internal capsule

Question 10

In the spinal cord grey matter, are fibers encoding flexors found more dorsal or ventral? Extensors?

Answer 10

Flexors - more dorsal (posterior)

Extensors - more ventral (anterior)

Question 11

What two structures are connected by the corticobulbar pathway?

Answer 11

Motor cortex to cranial nerve motor nuclei

Question 12

Which two tracts terminate in the cervical and thoracic spinal cord levels to innervate neck and trunk muscles and control their coordinated movements?

Answer 12

Vestibulospinal tract - provides info from the vestibular formation
Reticulospinal tract - provides info from reticular formation

Question 13

What does the rubrospinal tract participate in?

Answer 13

Involved in the control of arm muscles (travels closely with the lateral corticospinal tract)

Question 14

What is the function of the colliculospinal (tectospinal) tract? In what spinal region does it largely terminate?

Answer 14

Provides info from the superior colliculus to coordinate head movements with eye movements via innervate ion of neck muscles
(Terminates largely in the cervical region of spinal cord)

Question 15

A lesion in the corticospinal tract below the pyramids high in the cervical cord would cause weakness in what and on what side (relative to lesion)?

Answer 15

Arm and leg weakness on side ipsilateral to lesion

Question 16

Weakness in what part of body would be noticed if there was a corticospinal tract lesion below the cervical spine (what side, relative to lesion)?

Answer 16

Weakness in leg only, on side ipsilateral to lesion

Question 17

What deficits would be seen in a corticospinal lesion above the pyramids? What parts of body and what side relative to lesion)?

Answer 17

Weakness of face, upper, and lower limbs - all on the side contralateral to the lesion

Question 18

What is a Babinski sign? Its presence is indicative of damage to what?

Answer 18

It is a primitive extensor plantar response (and extension of the big toe) w/ fanning of the toes in response to stroking the lateral sole of the foot.
*Indicative of upper motor neuron lesion - normally upper motor neurons inhibit the reflex after 3-6 months

Question 19

What does testing of the muscle test reflexes do?

Answer 19

Assess integrity of both upper and lower motor neurons

Question 20

What is clonus?

Answer 20

A muscle stretch reflex that is unchecked and continues to operate through a feedback loop - ex. = repetitive plantar extension of the foot when foot is forcefully flexed upward

Question 21

Is clonus positive in lower or upper motor neuron lesions?

Answer 21

Upper motor neuron lesions

Question 22

Upper motor neuron lesions produce so called _________ motor responses, including clonus and Babinski.

Answer 22

Spastic - feature increased muscle tone andhyperactive muscle stretch reflexes; atrophy, fasciculations not seen

Question 23

Lower motor neuron lesions cause a ________ muscle response, including decreased reflexes.

Answer 23

Flaccid response - decreased muscle tone and decreased reflexes; atrophy and fasciculations are seen also