Download The Muscular System

The Muscular System
Functions

Stabilize joints with their tendons

Produce movement

Produce heat to maintain body
temperature

muscle – an organ that can relax,
contract, and provide force to move
your body parts.
Muscle Types

Voluntary – muscles you can control


hand, arm, leg, face…
Involuntary – muscles you cannot
consciously control
Continuously work all day
 heart, peristalsis, eyes…

Working Levers

The action of muscles, bones, and
joints working together is very similar
to a simple machine
Bones = rods
 Joints = fulcrum
 Muscle contraction/relaxation = force

3 Classes of Levers

1st class – the fulcrum lies between
the effort force and the load

2nd class – the load lies between the
fulcrum and the effort force

3rd class – the effort force is between
the fulcrum and the load
1st Class Lever
2nd Class Lever
3rd Class Lever
Skeletal Muscle

Muscles that move bone
Voluntary muscles that are striated
(striped)
 Contract quickly and tire more easily


Tendons – thick bands of tissue that
connect bones to muscles

Ligaments connect bone to bone to
form a joint
Skeletal Muscle
Cardiac Muscle

Found only in the heart
Striated, involuntary
 Contracts 70 times per minute

Smooth Muscle

Found in internal organs
Intestines, bladder, blood vessels…
 Nonstriated, involuntary muscles that
slowly contract and relax

Working Muscles

Pairs of skeletal muscles work
together


When one muscle pair contracts, and the
other one relaxes, or returns to original
length
Muscles always pull, they never push
When muscles are used they increase
in size (and sometimes number)
 However, when muscles are not used
they can shrink

Remember…
Muscles require energy to contract
and relax
 Blood carries energy filled molecules
to your muscle cells, then the stored
chemical energy is released


When a muscle uses all of its energy,
it becomes tired, and blood supplies
more energy-rich molecules to your
muscles while they are at rest