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23 Cards in this Set
- Front
- Back
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How do descending sys reg posture?
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1) Tonic excitatory bias 2) opening & closing spinal reflex pathways
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What is the central influence on spinal circuits?
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Long Latency Reflexes (which involve suprspinal & spinal circuits)
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How long are long & short latency reflexes?
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Long = 120msec Short = 50msec
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When are stretch reflexes facilitated?
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When they serve to stabilize posture. (i.e ankle extensor reflex is facilitated when a platform slides back & body sways forward.)
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When are stretch reflexes adapted?
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When they serve to destabize posture
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What is the function of righting reflexes?
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Maintain the top side uppermost (keep head oriented w/ respect to body or orient body in space. Compensate for change of center of gravity.)
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Descibe the tonic neck reflex during running or leaping.
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Dorsifexion of head produces forelimb ext & hindlimb flexion. Ventroflexion of head produces inhibition of forelimb ext & facilitation of hindlimb ext. (fixed attitude in relation to the ground)
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Describe the tonic neck reflex during lateral movement.
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Turning the head to the side of the direction of movement. (facilitate extensors on the same side of dir of movement & inhib flexors on opposite side. Extensor inhib &flex facil on opposite side prepare for 1st step)
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How can tonic neck reflexes be testes?
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Place patient on all fours
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How are the vestibular reflexes demonstrated in decorticate condition?
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Unturned head= arm flexion & leg ext. Turn head to right= flex left arm & leg ext. Turn head to left= flex right arm & leg ext
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What happens to the tonic neck reflex in decerebrate condition?
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Its released: head is dorsiflexed, arms & legs ext
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Where does rhythmic locomotion come from?
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Supraspinal centers; locomotor oscillators in cervical & lumbar enlargements
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How do pattern generators control limbs?
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Individual pattern generators for each limb (doesn't require other generators to function). Generators are coupled during walking.
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What does activation of gamma motoneurons cause? Why?
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Increases muscle spindle discharge during contraction.
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Why are alpha & gamma motoneurons coactive?
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Activation of onlt alpha would cause spindle to unload & reduce their discharge. Makes it difficult to keep measure fo muscle length
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What tracts influence locomation oscillators?
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Reticulospinal, Vestibulospinal, & MLR
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What does stimulation of MLR cause?
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Smooth locomotion in the decerebrate preparation
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How does SC afferents modulate locomotion by influencing the cerebellum?
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Dorsal & Ventra; Spinocerebellar tr are phasically active during loco
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What is the function of VSCT in locomotion?
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Transmitts central program from spinal generator to cerebellum (informs cerebellum about active proceses w/I the locomotion oscillators)
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What is the function of the DSCT in loc?
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Informs the cerebellum about the activity of muscles
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What is refle reversal?
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Stim that exaggerates a reflex is channeled to that muscle groups during the appropriate phase of walking.
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How does basal ganglia lesions affect loco?
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Problems initiating (akinesia), & stopping
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How do cerebellar lesions affect loco?
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Ataxia, dysmetria (range & direc of stepping affected). VSCT is never matched to DSCT)
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