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22 Cards in this Set
- Front
- Back
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Descending Pathway
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-work: monosynaptically (directly) or interneurons (indirect, majority) on alpha & gamma motor neurons of the ventral horn of the spinal cord
-both excitatory/inhibitory to other motor neurons |
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Lower Vs. Upper Motor Neuron
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LMN: alpha & gamma motor neurons/axons
-innervate extrrafusal muscle (alpha) & intrafusal muscle (gamma, spindle) -also include CN UMN: -"pyramidal system"- corticospinal tract (pyramid of medulla) -"extrapyramidal system"-rubiospinal, reticulospinal, vestibulospinal |
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Lateral Corticospinal Tract
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Origin: Primary motor cortex & frontal/parietal areas
Decussation: pyramidal Termination levels: entire cord (primarily cervical & lumbrosacral enlargement) Fxn: mvmt of contralateral limbs (executive motor planning ex: writing) |
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Lateral Corticospinal Tract Pathway
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UMN: primary motor cortex-->corona radiata (midbrain)-->internal capsule-->descend via cerebral peduncle (midbrain)-->pons-->medulla (85-90% fibers decussate to pyramids of medulla-->fibers continue down all levels of SC synapse at interneurons or ventral horn
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Anterior Corticospinal Tract
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Origin: primary motor cortex & supplementary motor area
No Decussation Termination Level: cervical & upper thoracic cord Fxn: synapse bilaterally, trunk musculature (girdle & axial) |
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Anterior Corticospinal Tract Pathway
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Cortex--> interna capsule --> midrain (cerebral peduncle)-->anterior pons-->medullary pyramid *DOESN'T cross*-->anterior column of SC synapses bilaterally: ventral horn or interneurons (mainly at thoracic)
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Rubrospinal Tract Pathway
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Origin: red nucleus (midbrain)
Decussation: ventral tegmental (midbrain) as they exit red nucleus Termination Levels: cervical cord Fxn: mvmt contralateral limbs (skilled dextrous mvmt UE) |
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Rubrospinal Tract
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Cerebral Cortex & Cerebellum-->Red Nucleus (midbrain)-->cross ventral tegmental deccesation-->Rubro's fibers run anterior to the lateral corticospinal tract in the lateral funiculus of the SC-->fibers terminate at all levels, but mostly cervical
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Reticulospinal Tract
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Origin: Pontine (medial) & Medullary (lateral) reticular formation
NO Decussation Termination levels: entire SC Fxn: automatice posture & gait-related mvmt |
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Reticulospinal Tract Pathway
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2 reticular formation regions (pons & medulla)-->pontine (medial) & medullary (lateral) reticulospinal tract:
-medullary: descends both crossed/uncrossed in anterior funiculus of SC--> inhibit LE extensors & facilitate flexors (reduce muscle tone) Pontine: descends mostly in ant. funiculus SC-->facilitates LE extensors (increase muscle tone) |
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Tectospinal Tract
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Origin: Superior Colliculus
Decussation: dorsal tegemental decussation in midbrain Termination Levels: Cervical Cord Fxn: Coordination of head/eye mvmt |
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Tectospinal Tract Pathway
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Cell bodies in Superior Colliculus (midbrain tectum)-->fibers cross in tegmentum (midbrain)-->enter descending portion of MLF-->run along medial vestibulospinal tract-->most terminate in cervical (interneurons)-->mediate reflex postural mvmt of head & neck in response to novel visual stimuli
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Vestibulospinal (medial and lateral)
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Origin: m-med/inf vestibular nuclei ; l-lat vestibular nuclei
No Deccusation Termin. Levels: m-cervical & upper thoracic ; l-entire cord Fxn: m-position of head & neck ; l-balance (support body against gravity, maintenance of upright posture) |
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Vestibulospinal Tract Pathway
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lateral:
lateral vestibular nucleus (deiter's nucleus)-->descends uncrossed in anterior funiculus-->terminate all levels-->primary anti-gravity pathway Medial: medial vestibular nucleus--> descends descending portion of MLF-->terminate on motor neurons in cervical & upper thoracic levels |
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Corticobulbar Tract Pathway
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fibers arise from face region of motor cortex-->descend corona radiata, internal capsule-->project/synapse w/ motor nuclei of CN in brainstem
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Corticobulbar Tract
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-CNs: III, IV, V, VI, VII, IX, X, XI & XII
-all cross except facial is bilateral Does not cross at decussation (crossed when needed) |
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Medial Longitundial Fascilculus
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-only motor ascending pathway
-arise from medialvestubular nucleus -ascend to synapse on motor nuclei of III, IV, VI (eye mvmt) -control vestibular ocular reflex (eye adjust to head mvmt) |
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LMN in SC
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-soma in ventral horn
-exit ventral root -synapse on NMJ (Ach) |
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LMN in Brainstem
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-soma in CN nucleus
-exit CN -Innervate muscle |
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LMN
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-form columns that may extend 1-2 segments of SC or whole pons, medulla,ect
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alpha-motor neuron
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-muscle mvmt
-skeletal muscle contraction -CN & ventral horn motor neurons to muscle (extrafusal skeletal) -larger in diameter, very fast signal |
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gamma-motor neuron
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-muscle spindle (stretch receptor for muscle)
-intrafusal muscle fibers of spindle -increase/decrease sensitivity for adjustment (if not firing, less sensative to stretch, if firing higher sensativity to stretch -smaller diameter & slower velocity |
