Exam #2: Motor Systems II Flashcards Preview

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Flashcards in Exam #2: Motor Systems II Deck (32):

What is the corticotectal tract?

Fibers that originate from the visual association cortex & descend into the tectum of the midbrian


Where do the corticotectal fibers terminate?

- Oculomotor Accessory Nuclei located near the oculomotor
- Superior Colliculus


Where do the axons of the oculomotor accessory nuclei project? What is their function?

To the nuclei of CN III, IV, & VI--producing reflex movement of the eyes

*****Occurs via the Medial Lemniscus


What is the general function of superior colliculus?

Reflex center of the midbrain for visual stimuli


What is the tectospinal tract?

These are projects from the superior colliculus in the midbrain to the spinal cord


What is the function of the tectospinal tract?

These projections from the superior colliculus produce reflex movements of the head & trunk in the direction of a startling stimulus


What is the pyramidal system?

This system consists of two tracts:
1) Corticonuclear tract (terminate in cranial nerves)
2) Corticospinal tract (terminate in spinal cord)
- Lateral corticospinal tract
- Anterior corticospinal tract


What is the function of the pyramidal system?

Conscious voluntary control of movement


What tracts are involved in the involuntary control of motor activity?

1) Reticulospinal
2) Vestibulospinal

****This is the system that coordinates subconscious/ background muscle tone, posture, & balance


What is the antiquated term for the system that maintains background muscle tone, posture, & balance?



What is the general function of the 1) Reticulospinal and
2) Vestibulospinal tracts?

Generation of subconscious muscle activity that modulates:
1) Muscle tone
2) Posture
3) Balance

*The pyramidal system superimposes its voluntary movement on this system; these systems work together


Outline the corticorubral tract

Corticorubral tract terminates in the red nucleus of the midbrain

*****Note that these axons can become intermingled with the corticospinal tract as they descend into the red nucleus of the midbrain


Outline the rubrospinal tract.

Arises from the red nucleus of the midbrain and descends into the spinal tract


What is the function of the corticorubral tract/ rubrospinal tract?

Stimulation of the extensor muscles of the upper limb i.e. hand and digit

****More important in lower primates but in humans, clinically fairly insignificant


Outline is corticoreticular tract. What are the reticulospinral tracts?

Arises from the cortex & descends via the carona radiata/ internal capsule into the reticular formation
- Reticulospinal tracts are the axons that descend from the reticular formation into the spinal cord


Where do the reticulospinal tract fibers terminate in the spinal cord? What is their function

Gamma motor neurons that synapse with the intrafusal fibers of the gamma loop
- Function in maintaining MUSCLE TONE

******Note that there are two divisions of the reticulospinal tract:
1) Medial (Pontine) reticulospinal tract (RST)
2) Lateral (Medullary) reticulospinal tract (RST)


What is the function of the Medial (Pontine) RST?

Stimulation of the paravertebral muscles & limb extensors

*****Thus, Medial Pontine RST= STANDING


What is the function of the Lateral (Medullary) RST?

Inhibition of paravertebral & limb extensor muscles

*****Thus, opposite of Medial Pontine RST: LYING DOWN


What are the two vestibulospinal tracts?

Generally, these tracts run from the vestibular nuclei of the pons to the spinal cord. There are two tracts:
1) Lateral VST
2) Medial VST


What is the function of the Lateral VST?

Stimulation of the paravertebral & proximal limb extensors

I.e. this has the SAME function as the Medial (Pontine) RST--STANDING


What is the function of the Medial VST?

This is a short tract that is involved in maintain the erect posture of the head


What CNS structure is central to maintaining balance? What is the pathway?


****Cerebellum-->Thalamus--> Motor cortex


Draw the spinal cord and label the location of the different descending motor pathways.

N/A Figure 5-9


What is the function of the anteromedial group of descending motor pathways?

Gross movement of axial & proximal limb musculature to maintain balance


What is the function of the lateral group of descending motor tracts?

Voluntary control of distal muscles in the hands i.e. controlling precise movements of the fingers


What is Brown-Sequard Syndrome?

This is a constellation of symptoms that occurs following hemisection (half) of the spinal cord


What are the manifestations of Brown-Sequard Syndrome?

1) UMN lesion signs ipsilateral
2) LMN lesion signs ipsilateral
3) Loss of reflex activity ipsilateral at the level of the lesion
4) Loss of fine touch ipsilateral
5) Loss of pain & temperature CONTRALATERAL


What is poliomyelitis? What part of the spinal cord is affected?

Viral destruction of neural tissue, specifically the cells of the ventral horn


What is Combined Systems Disease?

B12 def leading to damage of heavily myelinated axons located:
- Lateral corticospinal tract


Describe the arterial supply to the spinal cord.

Posterior 1/3= posterior spinal arteries (DC/ML)

Anterior 2/3= anterior spinal artery


What part of the spinal cord is most susceptible to interruption of blood flow?

Cervical b/c there is less anastamosis with the radicular arteries


What are the radicular arteries?

Blood vessels that supply the nerve roots of the spinal nerves

****Also, note that the radicular arteries anastaomse with the anterior & posterior spinal arteries