Muscle Function and Anatomy

Function of Muscle

Motion of joints Movement of body fluids - pump blood,

peristalsis Regulation of body fluids - bladder Body stability Heat production - 85%

Muscle Architecture

How Are Muscles Built?

In circular sections Deepest section

contains two proteins Myosin Actin

Myosin is surrounded by actin

Myofibrils

Bundles of actin and myosin

Muscle Fiber

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

Fascicle A group of muscle fibers bundled

together.

The Whole Muscle

The Whole Muscle

Muscle Membranes

Tendons All 3 membranes converge to form a tendon

which connects the muscle to the bone

Muscle Fiber Arrangement p. 25

Pennate muscles Greater cross sectional area – greater force

(strength) production

Parallel muscles Longer muscles – greater range of motion

Parallel muscles1. Flat (rectus abdominus)2. Fusiform (biceps)3. Strap (sartorius)4. Radiate (trapezius)5. Spincter Pennate1. Unipennate (biceps

femoris)2. Bipennate (rectus femoris)3. Multipennate (deltoid)

Muscle Fiber Arrangement

Strap

Types of Muscle Contraction p. 28

Isometric (Static) Isotonic (Dynamic)

Concentric Eccentric

Types of Muscle Contraction

Concentric contraction - If muscle force is greater than the resistance

Static or Isometric contraction - If muscle force is equal to the resistance

Eccentric contraction - If muscle force is less than the resistance

Lengthens Lengthens

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.

TABLE 2.1 Type of Contraction

Isometric

Isotonic

Concentric Eccentric

Agonist muscle No change Shortening Lengthening

Antagonist No change Lengthening Shortening

Joint angle No change In direction of force In direction of external resistance

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 Causes motion

Description Static Dynamic shortening Dynamic lengthening

Muscle force v. Resistance

F = R F > R F < R

Speed Equal to resistance Faster than the inertia of the resistance

Slower than the speed of gravity or applied inertial forces

Acceleration or Deceleration

Zero A D

Symbol = + -

ROLE OF MUSCLES

Agonist – prime mover Antagonist – have an action opposite to

the agonist Stabilizers – fixate or stabilize the joint Synergists – assist or guiding Neutralizers – counteract or neutralize

movements

Agonist and Antagonist

Types of Muscle Fibers

Fast twitch Slow twitch

Questions?