Efferent Motor Pathways - Upper Motor Neurons (10B) Flashcards Preview

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Flashcards in Efferent Motor Pathways - Upper Motor Neurons (10B) Deck (24)
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Where do upper motor neuron cell bodies originate?

In the precentral gyrus (primary motor cortex)


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

Brodmann area #4 - contains Betz cells


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

Brodmann area #6


What Brodmann areas are associated with the primary somatosensory cortex?

Areas 3, 1, 2


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

# 5 and 7


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?

Arm, trunk, leg

*corticobulbar fibers are located nearest the genu


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

Cerebral peduncle


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

Lower limbs = most dorsal-lateral
Upper limbs = most ventral-medial


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

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


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

Lateral (same as in posterior limb of internal capsule


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

Flexors - more dorsal (posterior)
Extensors - more ventral (anterior)


What two structures are connected by the corticobulbar pathway?

Motor cortex to cranial nerve motor nuclei


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

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


What does the rubrospinal tract participate in?

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


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

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)


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)?

Arm and leg weakness on side ipsilateral to lesion


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)?

Weakness in leg only, on side ipsilateral to lesion


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

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


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

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


What does testing of the muscle test reflexes do?

Assess integrity of both upper and lower motor neurons


What is clonus?

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


Is clonus positive in lower or upper motor neuron lesions?

Upper motor neuron lesions


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

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


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

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