Mechanics of Movement

Muscle Structure Review Muscle fiber = muscle cell Muscle fiber = muscle cell Fibers lined up = direction of pull Fibers lined up = direction of pull Tendon attaches to bone Tendon attaches to bone Muscle pulls on bone Muscle pulls on bone

Muscle Origin and Insertion Origin Origin – Proximal – Fixed Insertion Insertion – Distal – Moves (usually!!) (usually!!)

What is the origin? Origin- is the point where the muscle attaches to a stationary bone.

What is the insertion? Insertion- is the point where the muscle attaches to the moving bone.

Muscle Physics Length of muscle is proportional to ability to shorten (strain) Length of muscle is proportional to ability to shorten (strain) – Number of sarcomeres in series gives shortening ability Short, fat muscles Short, fat muscles – Lots of force – Less shortening range Long, skinny muscles Long, skinny muscles – Less force – More shortening range

Muscular movement of bones Generally skeletal muscles are attached to one end of a bone, stretch across a joint, and are fastened to the end of another bone. Generally skeletal muscles are attached to one end of a bone, stretch across a joint, and are fastened to the end of another bone.

Muscular movement of bones Muscles are attached to bones to form lever systems to create movement Muscles are attached to bones to form lever systems to create movement

Types of fascicle arrangements Affects length and cross section of muscle Affects length and cross section of muscle Thus affects force and shortening properties of muscle Thus affects force and shortening properties of muscle

MUSCLES & LEVERS  LEVER – simple machine for making work easier Three factors influence a lever: Three factors influence a lever: 1. Load – to be moved 2. Effort – needed to move the load 3. Fulcrum – point of balance

Muscle movement across joints is like lever system

First-class lever

Second-class lever

Third-class lever

Muscles attach to bone by tough connective tissue called what?

Tendons Tendons

Movement of the limbs

Muscles work in pairs to move a limb Muscles work in pairs to move a limb 1) Agonist1) Agonist 2) Antagonist2) Antagonist

Agonist "prime movers" "prime movers" responsible for generating a specific movement through its own contraction responsible for generating a specific movement through its own contraction

Antagonist acts in opposition to the specific movement generated by the agonist acts in opposition to the specific movement generated by the agonist responsible for returning a limb to its initial position. responsible for returning a limb to its initial position.

Stabilization and Control Around Joint AgonistMain MoverE.g. biceps AntagonistOpposite motionE.g. triceps SynergistAids agonistE.g. brachialis  Antagonist often “fires” or contracts or is stimulated simultaneously with agonist to stabilize around joint during movement  NOTE: Muscle “contraction” or stimulus to “fire” does not always result in muscle shortening

Agonist/Antagonist