The muscular system allows the body to move through the contraction and relaxation of muscles. There are over 600 muscles in the human body that work with the skeletal system. Muscles are categorized into three types - skeletal, smooth, and cardiac muscles - with skeletal muscles being voluntary and responsible for movement of the bones, while smooth and cardiac muscles are involuntary. Muscles contract when one muscle contracts while its opposing muscle relaxes, allowing movement, and muscles require energy to contract before needing rest.

1. MUSCULAR SYSTEM
7 SCIENCE: Wed. Nov. 2

2. What does the
muscular system do?
• Muscular system allows you
to move and your muscles
give your body shape
• Works with the skeletal system
• Do you know how many muscles are found in your
body?
– There are more than 600 muscles in your body
• Did you know that the number of muscles in your body
does not increase but the SIZE of the cell increases
instead
– If you do not do a lot of exercise with your muscles, your
muscles may become smaller and weak

3. What is a muscle?
• An organ that relaxes and contracts to allow
your body to move
• TWO types:
– Voluntary
• Arms and legs
– Involuntary
• Muscles of the heart

4. Types of muscle tissue
• There are 3 types of muscle tissue:
– Skeletal = move bones
• voluntary
– Smooth = move many
internal organs like
intestines and bladder
• involuntary
– Cardiac = only in the
heart
• involuntary

5. How do we
move using
our muscles?
• Muscles move because there are
2 muscles working together:
– One muscle contracts, the
other relaxes
• Muscles need energy, and when
energy is used up, the muscle
gets tired and needs to rest
Try it! Move your bicep muscle:
– CONTRACT: when you bend
your arm towards your elbow
and the muscle gets larger
– RELAX: when you move your
arm towards the ground and
the muscle flattens