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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 Chapter 2
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 • Among others things, a muscle fiber contains many groups of myofibrils
Muscle Architecture • Fascicle • A group of muscle fibers.
Tendons • Three membranes converge to form a tendon which connects the muscle to the bone
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
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
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
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
Concentric Concentric Lengthens Lengthens Eccentric Eccentric
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.
ROLE OF MUSCLES • Agonist • prime mover • Antagonist • action opposite to the agonist • Stabilizers • fixate or stabilize the joint • Synergists • assist or guiding
Agonist and Antagonist Agonist Agonist Antagonist Antagonist
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
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?