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  1. Internal torque
    the maximal internal torque potential is equal to the product of (1) the muscle force generated parallel to a plane and, (2) the length of the internal moment arm available to the muscle
  2. Spatial orientation of a muscle's line of force determines...
    its effectiveness for producing an action
  3. Horizontal vs Vertical forces
    • For a muscle to contribute all its force potential toward axial oration, its overall line of force must be directed solely in the horizontal direction.
    • For a muscle to contribute all its force potential toward either lateral flexion or flexion, its overall line of force must directed vertically
    • For all force potential, line of force must be in that plane
    • More of the total muscle mass of the trunk is biased vertically than horizontally.
  4. Activation within the axial skeleton
    • Bilateral: usually produces pure flexion or extension of the axial skeleton
    • Unilateral: tends to produce flexion or extension of the axial skeleton
  5. The action of a muscle within the axial skeleton depends on...
    the relative degree of fixation or stabilization of the attachments of the muscle
  6. axial skeleton assumed _____ end less contrained and moves over ____ end
    • superior
    • inferior
  7. Influence of Gravity. Action of muscle is ____, rotating body against gravity or some other external resistance
  8. Muscles of Posterior Trunk - Superifical
    • trapezius
    • latissimus dosi
    • rhomboids
    • levator scapula
    • serratus anterior
  9. Muscles of Posterior Trunk - intermediate
    • serratus posterior superior
    • serratus posterior inferior
  10. Muscles of Posterior Trunk - deep
    • erector spinae
    • tranversospinal
    • short segmental
  11. From superficial to deep, the deep muscles fiber length progressively gets..
  12. Erector spinae
    • - spinalis - lumborum, thoracis, cervicis
    • - longissimus - thoracis, cervicis, capitis
    • - iliocostalis - thoracis, cervicis, capitis

    **has a common tendon that anchors it to the axial skeleton by several direct or indirect attachments
  13. The erector spinal muscles cross a considerable distance along the axial skeleton. This anatomic feature suggests a design more suited for control of ___ movements of the entire axial skeleton that for control of ___ movements at individual intervertebral junctions.
    • gross
    • finer
  14. Erector spinae - bilateral vs unilateral contraction
    • bilateral contraction: extends trunk, neck, or head, can APT, accentuate lumbar lordosis (iliacus taut), or both
    • unilateral contraction: iliocostalis (laterally located): lateral flexors; longissimus and iliocostalis (cranial component) assist ipsilateral axial rotation; iliocostalis lumboum: assists slightly with ipsilateral axial rotation
  15. Forces Generated while Carrying Load
    • Ventral positioning of eyes and arms, external loads frequently carried or manipulated in front of body
    • lumbar extensor muscles (erector spinae) required to produce large internal forces in response
    • poor mechanical advantage (internal moment arm: external moment arm
  16. Transversospinal muscles
    immediately deep to erector spinae -- from TP of one vertebrae to spinous process of superior vertebrae

    • -semispinalis - superifical
    • - multifidi - intermediate
    • - rotatores - deep
  17. transversospinal fiber arrangment
    • most fibers aligned cranial-medial direction
    • vary in length and number of intervertebral junctions they cross
  18. semispinalis
    • thoracis
    • cervicis*
    • capitis*
    • *largest posterior neck muscles
  19. multifidi
    • originate TP and insert SP2-4 segments above
    • most developed LS
    • approach SP at nearing R angles - maximally converts force into a torque
    • essential source of extension torque and stability
    • excessive force (active contraction or protective spasm) - exaggerated lordosis
  20. rotatores
    • Best developed thoracic region
    • Brevis: spans 1 intervertebral junction
    • Longus: spans 2 intervertebral junctions
  21. Contraction - unilateral vs bilateral
    • • Relatively fine, controlled movements (compared to erector spinae)
    • • Contract Bilaterally: extend axial skeleton
    • • Greater developed either end of skeleton
    • – Cranially: semispinalis cervicis and capitis
    • – Caudally: multifidi

    • Contractunilaterally:
    • – Laterally flex spine (limited)
    • – More oblique assist with contralateral rotation
    • • Secondary axial rotators
    • • Leverage relatively poor due to proximity to vertebral column (compared to obliquus externus)
    • • Line of force more vertical than horizontal
    • – Greater potential for extension than rotation
  22. Short segmental group
    • Interspinalisand intertransversarus
    • – Each crosses 1 intervertebral junction
    • – Most developed cervical region
    • • Fine control of head and neck are critical

    • • Multiple pairs of short fibers extending entire vertebral column
    • • Highly segmented nature contributes to fine control
    • • Rich source of segmental sensory feedback
    • – Helps coordinate position of head and neck with visual and auditory systems
  23. interspinalis
    • – Located on either side of and often blend with interspinous ligament
    • – Favorable leverage for extension torque
    • • Relatively small due to small muscle size
  24. intertransversarus
    • – Located b/t adjacent TP
    • – Unilateral contraction, laterally flexes vertebral column
    • • Small
    • • Important source intervertebral stability
Card Set:
2011-10-09 19:51:14
spine muscles

tuesday quiz
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