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Muscle Function and Anatomy

Muscle Function and Anatomy. Chapter 2. Muscle Architecture. Muscle Architecture. Sections Deepest section contains two proteins Myosin (thick) Actin (thin) Myosin is surrounded by actin. Muscle Architecture. Myofibrils Bundles of actin and myosin. Muscle Architecture. Muscle fiber

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Muscle Function and Anatomy

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  1. Muscle Function and Anatomy Chapter 2

  2. Muscle Architecture

  3. Muscle Architecture • Sections • Deepest section contains two proteins • Myosin (thick) • Actin (thin) • Myosin is surrounded by actin

  4. Muscle Architecture • Myofibrils • Bundles of actin and myosin

  5. Muscle Architecture • Muscle fiber • Among others things, a muscle fiber contains many groups of myofibrils

  6. Muscle Architecture • Fascicle • A group of muscle fibers.

  7. The Whole Muscle

  8. The Whole Muscle

  9. Tendons • Three membranes converge to form a tendon which connects the muscle to the bone

  10. Shape of Muscles and Fiber Arrangement Strap • Parallel muscles (range of motion • Flat (rectus abdominus) • Fusiform (biceps) • Strap (sartorius) • Radiate (trapezius) • Sphincter • Pennate (force) • Unipennate (biceps femoris) • Bipennate (rectus femoris) • Multipennate (deltoid) Sphinter

  11. Muscle Tissue Properties • Irritability or Excitability • …to be stimulated • Contractility • …to contract (shorten) • Extensibility • …to be stretched • Elasticity • …return to original position after being stretched

  12. Muscle Terminology • Origin • proximal attachment • least moveable end • closest to the midline of the body • Insertion • distal attachment • most moveable end • furthest from the midline of the body • Action • The movement at the joint when the muscle(s) contract

  13. Types of Muscle Contraction

  14. Types of Muscle Contraction • Concentric contraction • Length of muscle shortens • Muscle force is greater than the resistance • If lifting 50 pounds and the muscle generates more than 50 pounds the muscle with shorten and move the weight. • Static or Isometric contraction • No change in muscle length • Muscle force is equal to the resistance • Lifting 50 pounds and the muscle generates 50 pounds of force • Eccentric contraction • Muscle lengthens • Muscle force is less than the resistance • Lowering 50 pounds and the muscle generates less than 50 pounds

  15. Concentric Concentric Lengthens Lengthens Eccentric Eccentric

  16. Eccentric Contraction • Used to control agonist and prevent over lengthening of the antagonist. • Example: triceps lowers dumbbell while biceps ’controls’ the triceps activity (action). • Causes more damage than other types • Greater repair required… • …producing a stronger muscle • Also, results in more muscle soreness.

  17. ROLE OF MUSCLES • Agonist • prime mover • Antagonist • action opposite to the agonist • Stabilizers • fixate or stabilize the joint • Synergists • assist or guiding

  18. Agonist and Antagonist Agonist Agonist Antagonist Antagonist

  19. Determination of Muscle Action • Muscle location • Origin and insertion • What joint(s) it crosses • Planes and their actions • Most muscle can not perform opposite actions (e.g. flexion AND extension) • Line of pull • Muscles only pull on bones, they do not push bones! • Insertion is pulled towards the origin

  20. Joint Actions • What joint does the muscle cross? • Where does the muscle cross the joint e.g. anterior, lateral, etc. • If the insertion end of the muscle is pulled towards the origin end, what action would result at the joint?

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