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Descending Pathways
Desc. Pathway PPT
Question | Answer |
---|---|
Reticulospinal Tract | RF= scattered cell groups Pons- axons to SC as pontine reticulospinal tract Medulla-axons to SC as medullary reticulospinal tract Both tracts neurons enter AHC, influences AMN/GMN, thus voluntary mvmts/reflexes Desc. ANS- hypothalamus control SNS/PNS |
Tectospinal Tract | From sup. colliculus/pre-tectal area above sup. colliculus Cross & desc close to MLF Neurons end in upper cervical AHCs |
Function of Tectospinal tract | Reflex postural adjustments related to visual stimuli; Fibers associated with SNS in lateral gray- pupillary reflex in response to darkness |
Rubrospinal Tract | In midbrain tegmentum- level of superior colliculus Cross & descend to SC |
Function of Rubrospinal Tract | Not entirely sure, may facilitate flexors & inhibit extensors |
Vestibulospinal Tract | Lateral vestibular nucleus->axons->lateral VST descend uncrossed through medulla & SC Internns to AHCs inhibit flexors, facilitate extensors to maintain balance Medial VST- only to C-spine, crossed, neck/head position mm |
Raphe Nuclei (RF) | Influence transmission of incoming sensory signals, motor responsiveness Influence pn transmission from peripheral nn, pre-ganglionic ANS & somatic motor nns |
Spinal & Ceruleus Spinal Projections | No mvmt, produce general excitatory/inhibitory effects that influence motor neuron response of CST to reflex-producing inputs (sleep-wake cycles & emotional changes) |
MLF- Descending in SC | pontine (medial) RST & medial VST; Supplies upper cervical; SC- MLF contains tectospinal tract (doesn't in the BS); Modulates reflex mvmts of head/neck in response to visual/vestibular stimuli |
MLF-Ascending in BS | fibers interconnect vestibular & extraocular nuclei; coordination of eye mvmt, integration of head/eye mvmts |
Lateral BS System | Fibers from contralateral red nucleus to SC via rubrospinal tract; Fibers from ventrolateral contralateral pontine & meduallary tegmentum via lateral columns of SC; ends in AHCs & DHCs |
Function of the Lateral BS System | Fine mvmts, discrete mvmt patterns; Facilitates flexors, inhibits extensors |
Ventromedial BS system | from nucleus of Cajal, sup. colliculus, mesencephalic, opntine & meduallary RF, & vestibular nuclei; Terminate in AHCs of axial/girdle mm |
Function of Ventromedial BS system | Maintenance of erect posture; integrate mvmts of body/limbs & progression mvmts of limbs; Facilitate extensors, inhibit flexors |
Lateral Reticulospinal Functions | Regulate ANS neurons in intermediolateral cell column |
Propriospinal Paths | from dorsal & ventral horn neurons, travel in white matter; link segments of SC to integrate local reflexes to coordinate body mvmts & visceral fxn |