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27 Cards in this Set
- Front
- Back
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Components of motor systems
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– ventral horn of SC, lower motor neurons of brainstem, upper motor neurons; cerebellum, basal ganglia, and brainstem derived upper motor neuron pathways important for motor function
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General motor pathway
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premotor/supplementary cortex -> motor cortex (pyramidal layer) -> SC (via corticospinal tract) and brainstem (via corticobulbar tract) ->striated muscle (LMN)
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Lower Motor Neurons
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Alpha ,motor neuron
Gamma motor neuron |
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alpha motor neurons characteristics
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large
in ventral horn innervate extrafusal muscle fibers (generate force) Type 1 Type 2b Type 2A |
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Gamma motor neurons characterisitics
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small, innervate intrafusal muscle fibers (detect stretch) of the muscle spindle, slower than alpha motor neurons
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autoimmune disease affecting NMJ, characterized by weakness of skeletal muscles due to circulating Ab that react with and block nicotinic ACh receptors in the postsynaptic membrane of the NMJ
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Myasthenia gravis
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Type I characteristics
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– slow twitch, sustained, red fibers – thin, lots of mitochondria, contract weakly and slowly, able to sustain long contractions, oxidative
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- Type IIB characterisitcs
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– fast twitch, fatigable, white fibers – larger, few mitoch, contract in brief powerful twitches
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- Type IIA characterisitcs
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fast twitch, fatigue resistant, intermediate fibers – moderate amount of force, sustained for moderate amount of time
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LMN Lesions
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diminished/absent tendon-jerk reflexes, flaccid paralysis, decreased resistance to passive movement, progressive atrophy, fibrillation potentials caused by random contraction of deinnervated muscles, sprouting neuronal branches at nodes of Ranvier and motor end plates
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UMN Lesions
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muscles, sprouting neuronal branches at nodes of Ranvier and motor end plates
6) UMN Lesions – absent/weak voluntary movements of affected muscles and lower face, absence of profound atrophy of muscles, spastic paralysis (continous reflex occurance), exaggerated tendon reflexes, positive Babinsky sign, superficial reflexes absent (abdominal, cremasteric) |
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Medial vestibulospinal tract goes from
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medial and inferior vestibular nuclei, descend with MLF, controls neck musculature
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b. Lateral vestibulospinal tract goes from
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from ipsilateral lateral vestibular nucleus, controls maintenance of upright posture (excessive activity ->decerebrate rigidity)
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b. Lateral (medullary) reticulospinal tract
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postural adjustment and balance maintance, alternative route for mediation of voluntary movement (ie: someone pushes you over but you catch yourself)
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Premotor cortex (preparation to move is
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bilateral coordination
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coordination of tactile and visual aspects of reaching and guiding movements
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Posterior parietal motor
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voluntary, precise, speedy, skilled movements
15) From agranule layer (Betz cells in layer V) – about equally from motor, premotor and supplementary motor, and parietal cortices |
Corticospinal tract
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Fine motor control pathway
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16) Cortex -> posterior limb of IC -> cerebral peduncle -> basilar pons-> pyramid (90% cross) -> lateral corticospinal tract in lateral funiculus -> alpha motor neurons in ventral horn
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Postural control pathway
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17) Cortex -> posterior limb of IC -> cerebral peduncle -> basilar pons ->pyramid (10% don’t cross) -> ventral corticospinal tract in ventral funiculus -> alpha motor neurons in ventral horn
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18) Lesion ABOVE decussation in medulla leads to
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contralateral paralysis
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Lesion BELOW decussation in medulla leads to
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ipsilateral paralysis
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Corticobulbar tract
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controls muscles of head, neck, and face
21) Cortex -> genu of IC ->cranial nuclei (bilateral innervations to 4,5,6,12 and nucleus ambiguous -9,10; ipsilataral innervations to 11) |
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Facial nucleus innveration of the face
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contralateral innervations of upper face, unilateral innervation of contralat lower face
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Lesion of facial nucleus
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paralysis of contralateral lower face
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ACA occlusion
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voluntary motor paralysis of leg (supplies superior area of motor cortex)
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25) MCA occlusion
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contralateral spastic hemiplegia/hemiparalysis of upper and lower extremities and positive Babinski sign (supplies rest of motor cortex and lenticulostriate branches supply IC
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Locomotor Generator: activated by
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descending fibers which terminate in reticular formation. It generates work in concert with vestibular system to initiate movement without any conscious input
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