Muscle Function and Anatomy Chapter 2 Muscle Architecture

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Muscle Function and Anatomy Chapter 2

Muscle Function and Anatomy Chapter 2

Muscle Architecture

Muscle Architecture

Muscle Architecture n Sections n Deepest section contains two proteins n Myosin (thick) n

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

Muscle Architecture n Myofibrils n Bundles of actin and myosin

Muscle Architecture n Myofibrils n Bundles of actin and myosin

Muscle Architecture n Muscle fiber n Among others things, a muscle fiber contains many

Muscle Architecture n Muscle fiber n Among others things, a muscle fiber contains many groups of myofibrils

Muscle Architecture n Fascicle n A group of muscle fibers.

Muscle Architecture n Fascicle n A group of muscle fibers.

The Whole Muscle

The Whole Muscle

The Whole Muscle

The Whole Muscle

Tendons n Three membranes converge to form a tendon which connects the muscle to

Tendons n Three membranes converge to form a tendon which connects the muscle to the bone

Shape of Muscles and Fiber Arrangement Strap n Parallel muscles (range of motion 1.

Shape of Muscles and Fiber Arrangement Strap n Parallel muscles (range of motion 1. 2. 3. 4. 5. Flat (rectus abdominus) Fusiform (biceps) Strap (sartorius) Radiate (trapezius) Sphincter n Pennate (force) 1. Unipennate (biceps femoris) 2. Bipennate (rectus femoris) 3. Multipennate (deltoid) Sphinter

Muscle Tissue Properties n Irritability or Excitability n …to be stimulated n Contractility n

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

Muscle Terminology n Origin proximal attachment n least moveable end n closest to the

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

Types of Muscle Contraction

Types of Muscle Contraction

Types of Muscle Contraction n Concentric contraction n Length of muscle shortens n Muscle

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

Concentric Lengthens Eccentric

Concentric Lengthens Eccentric

Eccentric Contraction n Used to control agonist and n n n prevent over lengthening

Eccentric Contraction n Used to control agonist and n n n 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 n Agonist n prime mover n Antagonist n action opposite to

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

Agonist and Antagonist Agonist Antagonist

Agonist and Antagonist Agonist Antagonist

TABLE 2. 1 Type of Contraction Isotonic Isometric Concentric Eccentric Agonist muscle No change

TABLE 2. 1 Type of Contraction Isotonic Isometric Concentric Eccentric Agonist muscle No change Shortening Lengthening Antagonist No change Lengthening Shortening Joint angle No change Decrease Increase Direction of body part Against immovable object Against gravity or external force Consistent with gravity or external force Motion Pressure but no motion Causes motion Description Static Dynamic shortening Dynamic lengthening Muscle force v. Resistance F=R F>R F<R

Determination of Muscle Action n Muscle location n Origin and insertion n What joint(s)

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

Joint Actions n What joint does the muscle cross? n Where does the muscle

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