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Muscular System

Muscular System. Origins & Insertions. Origin : Muscle attachment to the more stable bone; often closer to the trunk Reversal of muscle action when origin moves towards insertion Insertion : Muscle attachment to the more movable bone; often distal from the trunk

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Muscular System

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  1. Muscular System

  2. Origins & Insertions • Origin: Muscle attachment to the more stable bone; often closer to the trunk • Reversal of muscle action when origin moves towards insertion • Insertion: Muscle attachment to the more movable bone; often distal from the trunk • Insertion usually moves towards origin • Proximal: closer to the trunk • Distal: farther from the trunk

  3. Muscle Names • Muscle names may fall into one or more of the following categories: • Location • Shape • Action • Number of heads • Attachments (origin & insertion) • Direction of the Fibers • Size of the Muscle

  4. Muscle Fiber Arrangement

  5. Muscle Fiber Arrangement • Parallel Muscle fibers tend to be longer, with a greater ROM potential • Strap: long and thin c fibers running entire length of muscle (sartorius) • Fusiform: spindle shaped (biceps) • Rhomboidal: four-sided, flat shaped (rhomboids) • Triangular: flat & fan-shaped (pec major)

  6. Muscle Fiber Arrangement • Oblique muscle fibers tend to be shorter with greater strength potential, but decreased ROM • Unipennate: one side of a feather (post. tib.) • Bipennate: common feather (rectus femoris) • Multipennate: many tendons c oblique fibers in-between (deltoid)

  7. Functional Characteristics of Muscle Tissue • Five Properties of Muscles: • Normal Resting Length • Irritability • Contractility • Extensibility • Elasticity

  8. Functional Characteristics of Muscle Tissue • Normal Resting Length • Length of muscle when unstimulated

  9. Functional Characteristics of Muscle Tissue • Irritability • Ability of a muscle to respond to a stimulus. A muscle contracts when stimulated, either from a natural stimulus (motor nerve) or artificial stimulus (high volt electrical current)

  10. Functional Characteristics of Muscle Tissue • Contractility • Ability of a muscle to shorten (contract) • A muscle’s length may shorten, lengthen or remain the same length during contraction and stimulation • Isotonic and Isometric • Concentric and Eccentric

  11. Functional Characteristics of Muscle Tissue • Extensibility • The ability of a muscle to stretch or lengthen when a force is applied

  12. Functional Characteristics of Muscle Tissue • Elasticity • The ability of a muscle to recoil or return to normal resting length when the stretching or shortening force is removed

  13. Functional Characteristics of Muscle Tissue “Stretch a muscle and it will lengthen (extensibility). Remove the stretch, and it will return to its normal resting position (elasticity). Stimulate a muscle, and it will respond (irritability) by shortening (contractility).”

  14. Length-Tension Relationship in Muscle Tissue • Tension: The force built up in a muscle • Stretching builds passive tension • Contractile units control active tension

  15. Length-Tension Relationship in Muscle Tissue • Tone: The slight tension that is present in a muscle at all times, even at rest

  16. Length-Tension Relationship in Muscle Tissue • Excursion of a Muscle: The distance from maximum elongation to maximum shortening • A muscle is capable of being shortened to approximately one-half its normal resting length • A muscle can be stretched twice as far as it can be shortened

  17. Active and Passive Insufficiency • Active Insufficiency: Point at which a muscle cannot shorten any farther • Occurs to the agonist • Passive Insufficiency: Point at which a muscle cannot elongate any farther without damage to the muscle fibers • Occurs to the antagonist

  18. Muscle Contractions • Isometric Contractions: Muscle neither lengthens or shortens under load • Isotonic Contractions: • Concentric Contraction • Muscles shorten under load • Eccentric Contraction • Muscles lengthen under load

  19. Roles of Muscles • Agonist: muscle that causes motion • Antagonist: muscle that performs the opposite motion of the agonist • Biceps vs. Triceps • Cocontraction: agonist and antagonist contract together • Stabilizer: makes firm; allows agonist to work more efficiently • Abdominal muscles during a push-up (elbow extensors) • Neutralizer: prevents unwanted motion • Pronator teres neutralizes forearm supination during elbow flexion

  20. Kinetic Chains • Closed Kinetic Chain • Distal segment is fixed; proximal segment moves • Open Kinetic Chain • Distal segment moves; proximal segment is fixed

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