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What is the function of LMN?
produce muscle actions for reflexes and muscle tone
carry out UMN commands for voluntary movements and postural adjustments
What are some distinctive signs of a LMN lesion?
1) weakness of all movements (voluntary & automatic)
2) Diminished reflexes
3) Decreased muscle tone
What does the UMN consist of?
Direct and Indirect activation pathways
AKA pyramidal and extrapyramidal
What is the Direct Activation Pathway (pyramidal) and Indirect Pathway (extrapyramidal) Origin?
What is the Direct Activation Pathway and Indirect Activation Pathway destination?
cranial and spinal nerve nuclei
What is the function of the Direct Activation Pathway (Pyramidal)?
What are some distinctive signs of pyramidal lesions?
loss of skilled movement
decreased muscle tone
What is the function of the Indirect Activation Pathway or Extrapyramidal pathway?
control posture, tone, & movements supportive of voluntary movement
What are some distinctive signs of lesions to the extrapyramidal or indirect activation pathway?
hyperactive stretch reflexes
increased muscle tone
extended legs with resistance to bending (decorticate posturing)
excitation of all extensor muscles (decerebrate posturing)
The direct and indirect activation pathways, as well as the control circuits, are all part of the _______
What is NOT included in the UMN system?
The UMN system does NOT include the basal ganglia and cerebellar control circuits
Where does the direct activation pathway originate?
primary motor cortex (AKA, precentral gyrus, motor strip, or Brodmann's area 4)
What are the focal points of the pyramidal tract for speech?
primary motor cortex
supplementary motor area
On the premotor cortex, where are the cell bodies that innervate muscles of the face, including tongue, larynx, palate, jaw, face located?
lowest portion of the premotor cortex
What direct activation pathway innervation is bilateral?
CN 5 - Trigeminal
CN 7 Upper Face only
CN 9 - Glossopharyngeal
CN 10- Vagus
CN 11- Accessory
What is the function of the basal ganglia control circuit for speech?
regulation of slower components of speech for postural support, such as in articulation.
regulates muscle tone, movements associated with goal directed activities, such as arm swing during walking, automatic activities, such as chewing and walking, postural adjustments, learning new movements
What are the effects of damage to the basal ganglia control circuits?
Hypokinesia- disease of substantia nigra - inefficient dopamine
Affects segmental-phonemic linguistic speech
Hyperkinesia- excessive dopamine - involuntary movement, excessive unpredictable tone
What is the function of the cerebellar control circuit?
includes cerebellum structures
flocculonodular lobe-balance and orientation of head, regulates posture, gait, and trucal tone
Posterior lobe- coordinating skilled sequenced voluntary muscle activity
What is the function affecting speech of the cerebellar control circuit?
programming and coordinating more rapid speech movements
interprets feedback from speech muscles, tendons and joints to smooth speech production
What does damage to the the cerebellar control circuit cause?
depends on lobe that is effected
flocculonodular lobe-inability to stand or sit, swaying or falling, disturbances in gait, nystagmus
anterior lobe-gait ataxia
posterior lobe- limb ataxia, hypotonia, intention tremor, incoordination
What is the role of the basal ganglia and cerebellar control circuits?
speech programming and control
What is the function of corticobulbar pathway?
Involved in control of facial and jaw musculature, swallowing and tongue movements.
supplies CRANIAL LMNs
No major crossing
UMNs cross at the level of CNs they supply
What is the function of corticospinal pathway?
fine voluntary motor control of the limbs.
controls voluntary body posture adjustments.
What structures are in the extrapyramidal system?
cerebral cortex, Basal ganglia, thalamus, cerebellum, brainstem reticular formation, red nucleus, vestibular nuclei
Which of the following is associated with unilateral damage to the speech mechanism?
unilateral motor neuron damage
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