Download MUSCULAR SYSTEM

INTRODUCTION
Over 650 muscles make up the muscular
system
 Like the skeletal system, muscles are also
made up of cells, called sarcomeres
 Muscles are made of bundles of muscle fibers
that are held together by connective tissue
 When the muscle fibers are stimulated by
nerves, they contract

When muscles contract they become
short and thick
 Contraction causes movement

Without the muscular system we would
be unable to sit, stand, walk, speak, or
grasp objects
 Blood would not circulate, because there
would be no heartbeat to propel it
through the vessels
 The lungs could not rhythmically empty
and fill, nor could food move through the
digestive tract

FUNCTIONS OF THE SKELETAL
SYSTEM
Movement
 Posture and Body Position
 Support Soft Tissue
 Guard Entrances and Exits
 Involuntary Bodily Processes
 Thermogenesis

 Creation of heat
THREE KINDS OF MUSCLES
Cardiac
 Visceral or smooth
 Skeletal

CARDIAC

Found only in the wall of the heart

Contracts to circulate blood

Is an involuntary muscle
 functions without conscious thought or
control
VISCERAL OR SMOOTH

Found in the internal organs of the body
such as the digestive system,
respiratory system, blood vessels, and
eyes

Contacts to cause movement in these
systems

Also involuntary muscle
SKELETAL

Attached to bones

Causes body movement

Voluntary muscle
 We have control over these actions
FUNCTIONS OF SKELETAL
MUSCLES

Attach to bones to provide voluntary
movement

During contraction, they produce heat
and energy

Help maintain posture

Some protect internal organs
Characteristics of Muscles
 Characterized
by 3 things
1. Contractability: the ability to shorten
2. Excitable (irritable): allows them to
respond to stimulus
3. Elasticity: allows muscles to return to
their original length after being stretched
TENDON

Strong, tough connective tissue cord

Examples: achilles tendon, which
attaches the gastrocnemius muscle on
the calf of the leg to the heel bone
FASCIA

Tough, sheetlike membrane
 Covers everything!!

Covers and protects the tissue

Example: lumbodorsal fascia, which
surrounds the deep muscles of the trunk
and back
MUSCLE ATTACHMENT & FUNCTIONS

Have 3 main areas
 The belly
 Origin: a tendinous connection of the
muscle to a bone
○ usually the bone that is stabilized
 Insertion: a tendinous connection of the
muscle to a bone
○ Usually the bone to be moved
Muscle Attachment & Functions

Muscles are usually arranged in pairs
 Prime mover: causes main motion
 Agonist: opposing the main motion

Other muscles, called synergists, exist
to steady the movement of larger
muscles or to stabilize joint activity
Muscle Attachment & Functions

Muscles are controlled by a motor unit
 Motor unit = motor nerve and all muscle
fibers it stimulates
MUSCLE TONE
Muscles are partially contracted at all
times even though they may not be in
use
 This state of partial contraction is called
muscle tone
 Also described as a state of readiness to
act

LOSS OF MUSCLE TONE

Can occur in severe illness such as paralysis

When muscles are not used for a long period of
time, they can atrophy or waste away
 “Use it or lose it”

Lack of use can also result in a contracture
Muscle Tone

Muscle Atrophy
 Wasting away/loss of muscle tissue
 Results from disease or lack of use
 Immobilization from injury is a common
reason
MUSCLE TONE

Muscle Hypertrophy
 Increase in muscle mass
 Number of fibers to not increase, but the
already present fibers increase in size
 Commonly caused by exercise
 Must be exposed to training stimulus
sufficient to cause overcompensation in the
muscle