The
Muscular
System
How many muscles do you
have in the body?
Approximately 640 muscles!
Muscles make up
approximately 40% of your
body weight
Types of Muscles
Voluntary muscles – muscles you can
control by will or thinking
What is an example?
Involuntary muscles – muscles you cannot
control at will, but work automatically
What is an example?
Different Kinds of Muscles
Skeletal muscle (voluntary)
2. Smooth (involuntary)
3. Cardiac (involuntary)
1.
Skeletal

Striated muscles
 Holds the skeleton together
 Gives the body shape
 Helps with everyday movements
Smooth
 Controlled
by nervous system
automatically
 Examples
of smooth muscles are the walls
of the stomach and intestines, which help
break up food and move it through the
digestive system.
 Smooth muscle is also found in the walls of
blood vessels, where it squeezes the stream
of blood flowing through the vessels to help
maintain blood pressure
Cardiac
 Found
in the heart
 The walls of the heart's chambers
are composed almost entirely of
muscle fibers.
 Its rhythmic, powerful contractions
force blood out of the heart as it
beats.
How does movement occur?
 The
motor cortex sends an electrical
signal through the spinal cord and
peripheral nerves to the muscles, causing
them to contract
 The
motor cortex on the right side of the
brain controls the muscles on the left side
of the body and vice versa
The cerebellum coordinates the muscle
movements ordered by the motor cortex
Movement continued

Sensors in the muscles and joints send
messages back through peripheral nerves to tell
the cerebellum and other parts of the brain where
and how the arm or leg is moving and what
position it's in

Muscles move body parts by contracting and then
relaxing. Your muscles can pull bones, but they
can't push them back to their original position.

They work in pairs of flexors and extensors
What is the longest
muscle?
Sartorius
(Quadricep muscle)
What is the smallest
muscle?
Stapedius
(Inside the ear)
What is the widest
muscle?
External oblique
(Runs around the side of
the upper body)
What is the biggest
muscle?
Gluteus maximus
(In your buttock)
Sternocleidomastoid
 Location:
Side
of the neck
 Function:
Pulls
head back and
rotates head
Pectoralis Major
 Location:
Chest
 Function:
Brings arms
toward chest
Trapezius
 Location:
Upper
back and neck
 Function:
Moves shoulders
up and down
 Notes:
Shrugs
shoulders
Deltoid
 Location:
Surrounds the
shoulder joint
 Function:
Lifts
arm away from
body
Biceps
 Location:
Front
of the upper arm
 Function:
Pulls
lower arm up
(flexion)
Triceps
 Location:
Back of
upper arm
 Function:
Pulls
lower arm down
(extension)
 Notes:
extends
arm back
Latissimus Dorsi
 Location:
Down
the spine and
across the back
 Function:
Pulls
arm toward the
back
External Oblique
 Location:
Outside
part of trunk
 Function:
rotation
Trunk
Rectus Abdominus
 Location:
Center of
stomach
 Function:
Stabilize the
trunk area
Gluteus Medius
 Location:
Hip
area
 Function:
Lift leg
out to the side
Gluteus Maximus
 Location:
Buttocks
 Function:
Straightens hip
 Notes:
Sitting to
standing
Sartorius
 Location:
Inner side of
upper thigh
 Function:
inward
Pulls leg
Rectus Femoris
 Location:
Front
center thigh
 Function:
knee
Straightens
Vastus Lateralis
 Location:
Front
outside part of thigh
 Function:
Straightens knee
Vastus Medialis
 Location:
Front inner
part of thigh
 Function:
knee
Straightens
Biceps Femoris
 Location:
Back
outside thigh
 Function:
knee
Bends
Semitendonosus
 Location:
Back inside
thigh
 Function:
knee
Bends
Gastrocnemius
 Location:
Outside lower
back of leg
 Function:
Raises heel
Soleus
 Location:
Inside back
of lower leg
 Function:
Raises heel
Tibialis Anterior
 Location:
Front of
lower leg
 Function:
Pulls toes up