13. Motor Tracts Flashcards by Andrew Niemann

For motor tracts, instead of there being 3 neurons, there are only 2. What are they?

upper motor neuron (UMN)

lower motor neuron (LMN)

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What are two examples of both UMN and LMN?

UMN: Corticospinal and corticobulbar (corticonuclear) tracts
LMN: Peripheral and Cranial Ns

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What is the difference between direct and indirect somatic motor pathways?

direct from cerebral cortex to spinal cord to muscles

indirect includes synapses in BS, basal gang, thalamus, reticular formation and cerebellum

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The corticospinal tract is a direct pathway which controls voluntary motion. UMN arise from cortex and synapse in SC on LMN. What are the two paths?

Medial corticospinal tract (postural)

MAIN: lateral corticospinal tract (90%) - muscles/fine movement

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What is the general overview/pathway of the corticospinal pathway? 8

Cell bodies in cortex
Descends through posterior limb of internal capsule
Continues as lateral corticospinal tract
Passes through midbrain at cerebral peduncles
Through anterior pons
Through pyramids of medulla
Fibers cross in LOWER medulla pyramids
Descend in lateral column of spinal cord and synapase with LMNS

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The primary motor cortex (brodmanns area 4) is in the precentral gyrus. The right side motor strip usually controls?

left side of body and vice versa

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Muscles in the homunculus are represented unequally according to the number of motor units in a muscle. What are examples of areas with more motor units? (5)

vocal cords
tongue
lips
fingers
thumb

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What is the difference between corticospinal and bulbar tracts? Where are they located in the internal capsule?

Corticobulbar is face motor and located in GENU of internal capsule
Corticospinal is arms thorax and legs and located in posterior limb of internal capsule

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When the lateral corticospinal tract descends and crosses at the lower medulla, not all cross. What are the two different tracts called?

medial corticospinal tract (not many-dont cross)

lateral corticospinal tract (cross)

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The lateral corticospinal tract after crossing in lower medulla will descend in the lateral column of the spinal cord and synapse where?

Synapses on LMNs in the VENTRAL horn of spinal cord

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What are the two main blood supplies to the corticospinal tract in the internal capsule?

lenticulostriate A

anterior choroidal A

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What is the main blood supplies to the corticospinal tract in the midbrain?

posterior cerebral A

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What are the two main blood supplies to the corticospinal tract in the medulla?

anterior spinal A via sulcal A

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What are the main blood supply to the corticospinal tract in the pons?

paramedian branches of basilar A

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What are the two main blood supplies to the corticospinal tract in the spinal cord?

Anterior and posterior spinal A

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The 10% of the corticospinal tract that does not cross becomes the medial corticospinal tract and has no clinical significance. What does it control?

postural and proxiaml movements (neck shoulders trunk)

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The corticobulbar/nuclear tract arises from the lateral precentral gyrus, descends and influences muscles innervated by CNs. Which ones? (6) (axons cross)

5,7,8,10,11,12

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The corticobulbar tract follows the same path as the lateral corticospinal tract except for what region?

in cortex, corticobulbar tract descends through the genu of the internal capsule

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In the mid pons, what does the corticobulbar tract give off?

bilateral fibers to trigeminal motor nucleus

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In the lower pons, what does the corticobulbar tract give off?

Bilateral facial forehead, only one side innervates mouth

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In the medulla, what does the corticobulbar tract give off?

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Contralateral fibers to hypoglossal and ambiguus nucleus (CN 9/10/12)

What influence does the corticobulbar tract have on CN XI?

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ipsilateral

Remember, the LMNs are located in the ventral horn of spinal cord and are topographically organized. What are the four sections?

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medial: proximal motor neurons
lateral: distal motor neurons
ventral: extensory motor neurons
dorsal: flexor motor neurons

Indirect pathways are all from UMNs and tonically activate antigravity and axial LMNs (basal firing rate) what are the Medial UMN and Lateral UMN indirect tracts? (4,2)

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medial:  (are within anterior funiculus)
tectospinal
medial reticulospinal
lateral vestibulospinal
medial vestibulospinal
Lateral:
rubrospinal (right next to lateral corticospinal)
lateral reticulospinal

What indirect tract starts in the lateral vestibulospinal nuclei of the PONS, goes to SC and synapses ipsilateral LMNs for posture and limb extensors?

lateral vestibulospinal tract

What indirect tract starts in the MEDULLA in medial vestibular nucleus and goes to SC and gives gravity/accelaration to cerival/T2/3 muscles?

Medial vestibulospinal tract

What indirect tract starts in the PONS in the pontine reticular formation and goes to ventral horn LMNs SC, providing ipsilateral postural and limb extensors?

medial (pontine) reticulospinal tract

What indirect tract starts in the MEDULLA at the medullary reticular formation and goes to SC to facilitate flexor motor neurons and inhibit extensor motor neurons? (inhibits tone)

lateral (medulla) reticulospinal tract

What indirect tract starts in the red nucleus of the MIDBRAIN and crosses before it gets to the pons, and innervates upper limb flexors?

Rubrospinal tract

What indirect tract that may be rudimentary starts in the superior colliculus in MIDBRAIN and goes to UPPER SC to help with visual reflex? (neck muscles to move to stimulus)

tectospinal tract

In lower motor neuron LMN lesions where the final common pathway is damaged. What are the common symptoms seen? 5

``` Flaccid paralysis Atrophy Hypo/areflexia Hypotonia Fasciculations ```

What is a combination of the loss of corticospinal tract and loss of regulation from indirect brainstem motor control pathways?

Upper motor nucleus (UMN) damage/lesion

What are the common symptoms/signs seen with UMN lesions/damage? (5)

``` No strength Babinski sign (toes pop up) Hypertonia = (SPASTICITY AND RIGIDITY) Hyperreflexia CLONUS Clasp-knife/Pronator drift ```

LMN lesions will have signs on the same side as lesion. How about UMN lesions?

Above lower medulla where crosses (like PCMLS) contralateral side affected Below lower medulla where hasnt crossed, ipsilateral side affected

Spinal cord lesions of the UMN and LMN will show signs where?

UMN: below level of lesion (same as PCMLS) LMN: AT level and down

What UMN lesions is above the red nucleus (could also be due to herniation of brain)?

Decorticate posture/rigidity

What are the common signs of decorticate posture? 4

Fist postion pronation forearms flexion at elbows lower extremity in extension w foot inversion

What UMN lesions is below the red nucleus but leaves reticulospinal and vestibulospinal nuclei in tact?

Decerebrate posture/rigidity

What are the common signs of decerebrate posture? 2

upper extremity pronation and extension | lower extremity extension

If the corticospinal tract CST or PCMLS is lesioned in the cortex, where would the deficits be?

contralateral body

If there was a lesion in the spinal cord of the PCMLS, CST where would the decificits be?

ipsilateral body because fibers haven't crossed

What can be seen with a complete transection of the spinal cord? 5

``` All sensation 2 levels below lesion gone (2 levels because dermatomes overlap) Bladder/bowel control lost spinal shock UMN signs below lesions LMN signs at lesion ```

What can be seen with a hemisection of the spinal cord, also known as Brown-Squard's syndrome? 4

UMN signs on ipsilateral side (CST) LMN signs at level of lesion (Ventral horn) Loss touch and proprioception on ipsilateral side (PCML) Pain and temp from contralateral side (ALS/spinothalamic)

Syringomyelia is formation of cysts within the spinal cord at C4/5 and can enlarge and cause problems. What will be affected first to last? 3

1. Anterior white commissure (pain/temp) = shawl/cape 2. Ventral horn (LMN) 3. Lateral corticospinal tract (UMN)

What is seen with anterior spinal cord syndrome? 4

lateral corticospinal tract (ips), lateral spinothalamic tract (cont cause pain fibers cross immediately), ventral horn (ips) PCMLS will be FINE cause in posterior

What is seen in central cord syndrome, which is much like syringomyelia? 3

AWC = bilateral pain/temp sensory Anterior horn LMN Lateral corticospinal tract UMN

In medial medullary (dejerine) syndrome, the pyramids, medial lemniscus and hypoglossal nucleus is damaged possibly due to Anterior spinal A occlusion. What deficits can be seen?

pyramids: contra UMN ML: contra prop/touch CN XII: protrudes tongue, deviates toward

In lateral medullary (wallenburgs) syndrome, Inferior/medial vestibular nucleus, inferior cerebellar peduncle, spinal trigeminal tract/nucleus and nucleus ambiguus is damaged. What can be seen? (not cerebellar)

Contra loss pain/temp to body spinal trigem: ipsilat loss pain/temp face NA (CN9/10): hoarsness/say ah/ cant swallow

What is seen in central seven palsy?

if there is a lesion in the right cortex-corticobulbar, the left mouth will droop but the forehead will be fine because it is innervated by both facial N

Webers syndrome in the midbrain will affect CST, CBT, and CNIII... what can be seen?

contralateral UMN contra lower face, uvual deviates TOWARD, tongue away LMN down lateral eye, dilated pupil

What destroys somatic motor neurons in UMNs and LMNs resulting in paresis, hyperreflexia, babinskis, atrophy, fasciculations and fibrillations?

Amyotrophic Lateral Scelrosis (ALS) Death see both UMN and LMN symptoms

What involves sensory motor and autonomics, and progresses from distal to proximal. Commonly seen as stocking glove presentation?

Polyneuropathy

13. Motor Tracts Flashcards

(52 cards)