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 deeperinternus.
• Structure: biceps- has two heads,
triceps- has three , and quadriceps- has
four.
Naming Muscles
• Shape: Trapezius- trapezoid,
Deltoid-triangular, Orbiculariscircle.
• Size: larger muscles- Major,
smallest- Minor, long musclesLongus.
• 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