The Muscular System

Chapter 11

Anatomy and Physiology

Mr. Knowles

Liberty Senior High School

You can’t talk about the physique without a little

physics first!

The Physics of the Muscular System

• Tension- an active force applied to some object that requires energy. Ex. People pulling on a rope, the PULL is the tension.

• When muscle cells contract, they PULL on the connective tissue, tendons.

The Physics of a Physique

• Compression- another active force that PUSHES an object AWAY from the source.

• Resistance- a passive force that OPPOSES movement that depends on weight, shape, friction, etc.

The Laws of Muscle Physics• When the Tension > Resistance =

Movement.• The object is pulled toward the source

of the tension. Muscle cells can ONLY shorten and generate tension, NOT lengthen to generate compression.

Tension and Muscles• The amount of tension a muscle can

generate is related to the number of resting sarcomeres it has. The more sarcomeres the more tension.

• Some muscles contract and pull against tendons or sheets of collagen called –aponeuroses at their ends.

Structure and Function of Muscles

Structure Function• Some work across joints movement.

• Others support soft tissue form slings.

• Still others completely

encircle openings sphincters.

Organization of Skeletal Muscle Fibers

• Muscle fibers form bundles called …???? Fascicles!

• The fibers within a single fascicle are parallel BUT the organization of the fascicles, themselves, can vary.

Four Patterns of Fascicle Organization . . .

• Parallel Muscles

• Convergent Muscles

• Pennate Muscles

• Circular Muscles

Parallel Muscles• The fascicles are parallel to the

long axis of the muscle. Most common type of muscle.

• The muscle is spindle-shaped with a central body (belly) or gaster.

• Example: biceps brachii

Parallel Muscles

Convergent Muscles

• The muscle fibers are based over a broad area, but all the fibers come together at a common attachment site.

• Fibers spread out like a fan• Example: pectoralis major

Convergent Muscles

Pennate Muscles• The fascicles form a common angle

with the tendon.• Contracting pennate (feather) muscles

do not move their tendons as far as parallel but contain more muscle fibers which produces more tension.

Three Types of Pennate Muscles

• Unipennate: extensor digitorum

• Bipennate: rectus femoris

• Multipennate: deltoid

Unipennate: extensor digitorum

Bipennate: rectus femoris

Multipennate: deltoid

Circular Muscles• Fibers are concentrically arranged around

an opening or recess. When the muscle contracts, the diameter of the opening decreases.

• Guard entrances & exits of internal passageways; sphincters.

• Example: orbicularis oris

Circular Muscles

Tension of a Muscle

• Related to the length and number of the resting sarcomeres it has.

• The tension a muscle provides can change through the movement.

• Ex. The biceps brachialis through a curl.

Muscle Work Together• Complex movements require several muscles to

work together for efficiency.• Large limb muscles may not reach maximum

tension until part way through the motion. Need smaller muscles to assist.

• At the start of the movement, smaller muscles produces maximum tension, while the larger muscle produces minimum tension until much later.

General Names of Muscles• Prime Mover or Agonist- a muscle whose

contraction is mainly responsible for the movement. Ex. Biceps.

• Antagonists- are prime movers whose actions oppose a particular agonist. Ex. Triceps to the biceps.

• Synergist- usually smaller muscles that assist the prime mover in performing an action; usually important at the beginning.

Muscle Terms• Every muscle has a beginning- origin and

an end- insertion. The movement produced is the action.

• Origins- remains stationary during the movement; usually proximal to the insertion.

• Insertions- changes its position during the movement.

Muscle Terms

• Action- is the motion produced by the contraction of the muscle(s). Usually across a joint.

Naming Muscles

• Some names refer to fascicle organization:Rectus- “straight,” parallel muscles to the long axis of the body.

• Often combined with a term describing precise location:Rectus abdominis, Rectus femoris.

Naming Muscles

• Directional terms:Transversus or Obliquus- fibers that run at an oblique angle to the long axis of body. Lateralis- lateral muscles.Medialis- more medial muscles.

Naming Muscles

• Location: names may specify a certain region of the body. Ex. Temporalis- head, Brachialis-arm.

• Relative Position: muscles close to the surface-externus, those deeper-internus.

• Structure: biceps- has two heads, triceps- has three , and quadriceps- has four.

Naming Muscles• Shape: Trapezius- trapezoid, Deltoid-

triangular, Orbicularis-circle.• Size: larger muscles- Major, smallest-

Minor, long muscles-Longus.• Action: based on the motion; flexor,

extensor, abductor, adductors.

Other Location Names

• Oris- refers to the mouth.

• Oculi- refers to the eye.

The Muscle Insertion and Origin Activity