Term
| What are the two major functional groups of the brainstem descending pathways? |
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Definition
1. Medial systems (posture)
2. Lateral systems (fine dextrous movements) |
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Term
| What are the two tracts in the medial system (the brainstem descending pathway)? |
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Definition
1. Vestibulospinal tract
2. Reticulospinal tract |
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Term
| Describe the vestibulospinal tract (the brainstem descending pathway) |
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Definition
Originate in vestibular nuclei and project to spinal cord
-Uncrossed (ipsilateral)
-Mainly excites extensors and inhibits
flexors |
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Term
| Describe the reticulospinal tract (the brainstem descending pathway) |
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Definition
-Originate in medullary and pontine reticular formation and project to spinal cord
-Mainly uncrossed
-Pontine reticulospinal tract mainly excites extensors and inhibits flexors, and medullary reticulospinal tract mainly excites flexors and inhibits extensors |
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Term
| What are the two tracts in the lateral system (the brainstem descending pathway)? |
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Definition
1. Corticospinal tract
2. Rubrospinal tract |
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Term
| Describe the corticospinal tract (the brainstem descending pathway) |
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Definition
-Originates in cerebral cortex
and projects to spinal cord
-Crossed (85%)
-Mainly excites flexors in distal limbs and digits, and inhibits extensors. |
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Term
| Describe the rubrospinal tract (the brainstem descending pathway) |
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Definition
-Originates from red nucleus in midbrain and projects to spinal cord
-Crossed
-Mainly excites flexors in proximal limbs and hands, and inhibits extensors |
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Term
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Definition
| Any area that, when stimulated, produces some sort of movement |
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Term
| What is the difference between the primary motor cortex and the premotor cortex? |
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Definition
The primary motor cortex produces focal movements under low intensity
Premotor cortex requires high intensity and moves groups of muscles |
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Term
| Describe the frontal eye fields. Are they in the motor cortex? |
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Definition
| Although considered to be motor cortex, do not connect with the primary motor cortex; instead, they project to regions controlling saccadic eye movements |
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Term
| How is the primary cortex organized? |
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Definition
Stomatopically, with the leg on the medial surface and the face more inferior
Larger areas for fingers and mouth, for finer movements |
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Term
| Is the primary motor cortex contralateral? |
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Definition
| Yes, but it normally influences unilateral movements. The contralateral input is more of a "backup" control for distal limbs in the event of lesion. |
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Term
| Define fractionated movements |
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Definition
The finely controlled, dexterous movements across a single joint, which permit the detailed coordinated movements of our fingers and hands.
Executed by the primary motor cortex |
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Term
| What is the role of the supplementary motor cortex (aka medial premotor cortex)? |
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Definition
| To coordinate bilateral movements on both sides of the body, adjust posture needed for a movement, and to mentally rehearse movements |
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Term
| What is the role of the lateral premotor cortex? |
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Definition
| Coordinating unilateral movements, performing correct movements related to the environment (ex. catching a ball), adjust posture as needed |
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Term
| How are the supplementary motor cortex and lateral premotor cortex organized? |
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Definition
| Stomatopically, but less so than the primary motor cortex |
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Term
| What is the role of the cingulate motor cortex? |
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Definition
| Not understood, but may have functions similar to the supplementary motor cortex or can be involved in showing emotion with the limbic system |
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Term
| What is the role of the frontal eye field |
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Definition
| To control voluntary conjugate saccadic eye movements (the fast eye movements) |
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Term
| Describe stimulation/lesion results in the frontal eye field |
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Definition
| Stimulation of the frontal eye field on one side causes saccadic eye movements toward the opposite side; a lesion produces eye deviation toward the side of the lesion. |
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Term
| What two regions of the cortex do not ultimately project to alpha motor neurons, but do influence movements? |
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Definition
| Somatosensory cortex, posterior parietal lobe |
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Term
| What is the role of the somatosensory cortex in movement? |
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Definition
Receives somatosensory input and relays this information to the complementary motor region
Descending output influences sensory input; can modulate sensory input to a level appropriate for an occasion. |
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Term
| What is the role of the posterior parietal lobe in movement? |
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Definition
| Coordinates visual (spatial) information with movement (the dorsal "where" pathway) |
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Term
| In the corticospinal tract, from where do the fibers originate? |
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Definition
30% primary motor cortex
30% premotor areas
40% somatosensory cortex |
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Term
| Define lower motor neuron |
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Definition
| Spinal motoneurons or nerves, or cranial nerve motor neurons |
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Term
| Define upper motor neuron |
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Definition
Refers to corticospinal neurons or other descending neurons above
spinal cord |
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Term
| What are signs of damage to lower motor neurons? |
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Definition
1. Decreased muscle tone
2. Muscle atrophy
3. Muscle fasciculations or fibrillations of single fibers
4. Absence of tendon reflexes
5. No Babinski sign |
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Term
| What are signs of damage to upper motor neurons? |
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Definition
1. Decreased muscle tone (hypotonia) initially, becoming increased muscle tone (hypertonia, spasticity) with time
2. Rarely have muscle atrophy
3. Affects groups of muscles instead of a single muscle
4. Enhanced stretch reflexes (hyperreflexia)
5. Babinski sign present |
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Term
| What is the Babinski sign? |
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Definition
Extensor plantar response
Normal response: stroke lateral aspect of foot with sharp object causes flexion of toes
Damage to pyramids (corticospinal tract): Big toe invariably extends, and other toes frequently fan out. |
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