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Motor speech lecture 7
Motor pathways
31
Science
Graduate
10/04/2010

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Term
The motor system is essential to...
Definition
normal reflexes; maintaining muscle tone & posture; and planning, initiating, & controlling voluntary movements
Term
system components of the motor system
Definition
cortex/efferent connections; basal ganglia; cerebellum, motor nuclei in brainstem (cranial & spinal)/efferent tracts; striated muscle
Term
pyramidal tract
Definition
direct motor system; two primary nerve tracts that together form part of the upper motor neuron system.
Term
name the two tracts of the upper motor neuron system
Definition
corticobulbar and corticospinal
Term
corticobulbar tracts
Definition
carries information directly from the cortex to the cranial nerves
Term
corticospinal tracts
Definition
carries information directly from the cortex to the spinal nerves
Term
what are upper motor neurons?
Definition
neurons controlled by the cortex, cerebellum & basal ganglia that regulate LMNs or final common pathway.
Term
What is the direct connection between the cortex & final common pathway?
Definition
Cortex primarily facilitate finely controlled, discrete movements (through UMN)
Term
____% of fibers decussate at the medulla
Definition
90
Term
UMN in the corticospinal tract innervates...
Definition
LMN on the opposite side of the body
Term
Describe pyramical tract destination of the corticobulbar tract.
Definition
most speech UMNs bilaterally innervate LMNs; technically, many tracts first run through the reticular system before terminating with the actual LMN nuclei
Term
What is the function of the pyramidal tract?
Definition
voluntary motor functions- conciously controlled, skilled, discrete, rapid movements
Term
what are the effects of pyramidal tract lesions?
Definition
loss or reduced skilled movements; usually not as bad at LMN lesions; for corticospinal lesions, weakness on opposite side of the body; reflexes usually not lost.
Term
whatr are the effects of corticobulbar tract lesions?
Definition
effects on speech are minor; some tongue weakness, contralateral lower facial weakness;
Term
unilateral UMN lesions of the corticobulbar tract have what effect on speech?
Definition
very mild speech dysarthria
Term
Bilateral UMN lesions of the corticobulbar tract have what effect on speech?
Definition
spastic dysarthria (very spastic)
Term
What are the components of the indirect motor system?
Definition
corticoreticular tracts, corticorubral tracts, Reticular formation; vestibular nuclei; red nucleus
Term
corticoreticular tracts
Definition
from cortex to reticular formations in the brainstem that intermingle with CS and CB tracts.
Term
corticorubral tracts
Definition
from cortex to red nucleus --coordinates muscle tone body position and gait.
Term
reticular formation
Definition
ill-defined neuronal system scattered throughout the brainstem; "seat of consciousness"; mediates ascending sensory information; helps integrate sensory-motor functions; complex effects on LMNs
Term
vestibular nuclei
Definition
located in the floor of 4th ventricle in Pons and medullar; received sensory information from ear and cerebellum; contribute to muscle tone, esp in spinal and reflex mechanism; role in speech is uncertain
Term
Red nucleus
Definition
found in the brainstem; has both sensory & motor functions; speech role is unclear; has a major role with flexor muslces in the limbs.
Term
What are the functions of the indirect motor system?
Definition
regulates reflexes; helps maintain postures, muscle tone, provides neuromuscular framework for Pyramidal Tract to accomplish skilled discrete actions.
Term
what roll does the indirect motor system play in speech function?
Definition
ensure specific speech movements occur without constant or variable interference with their speed, range & direction.
Term
decorticate posturing of the indirect system
Definition
corticoreticular tracts above midbrain produce increased extensor tone in legs and increased flexor tone in arms.
Term
what is extensor tone?
Definition
legs extended; resist bending
Term
What is flexor tone in arms?
Definition
arms flexed; resist extension
Term
What is decerebrate posturing?
Definition
lesions below the midbrain produce extensor tone increase in both arms and legs (resist bending)
Term
flaccidity
Definition
lesions below the medulla or cranial nerves result in loss of all descending input to muscles suppled by spinal system
Term
spasticity
Definition
When cortical controls are completely cut of ABOVE BRAINSTEM, reticular formation goes unchecked; extensor muscles become hyperexcited.
Term
UMN lesions of the indrect system affect ...
Definition
both direct & indirect systems; usually spasticity; increased muscle stretch reflexes; direct skilled movements lost; indirect control lost
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