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

Different Kinds of Muscles Skeletal muscle (voluntary) Smooth (involuntary) Cardiac (involuntary)

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: Trunk rotation

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: Pulls leg inward

Rectus Femoris Location: Front center thigh Function: Straightens knee and bends hip

Vastus Lateralis Location: Front outside part of thigh Function: Straightens knee

Vastus Medialis Location: Front inner part of thigh Function: Straightens knee

Biceps Femoris Location: Back outside thigh Function: Bends knee and straightens hip

Semitendonosus Location: Back inside thigh Function: Bends knee and straightens hip

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