normally do. For example, if you run, you can rest your running muscles and joints by
swimming. This type of rest is calledactive rest.
Anabolic steroidsare hormones that cause the body to build up more protein in its cells.
Muscle cells, which contain a lot of protein, get bigger when exposed to anabolic steroids.
Your body naturally makes small amounts of anabolic steroids. They help your body repair
from injury, and help to build bones and muscles. Anabolic steroids are used as medicines to
treat people that have illnesses that affect muscle and bone growth. However, some people
who do not need anabolic steroid as medicine try to increase their muscle size by taking these
steroids. When taken in this way, anabolic steroids can have long-term affects other body
systems. They can damage the person’s kidneys, heart, liver, and reproductive system. If
taken by adolescents, anabolic steroids can cause bones to stop growing, resulting in stunted
growth.
Lesson Summary
- The body has three types of muscle tissue: skeletal, cardiac, and smooth. Muscles
move the body by contracting against the skeleton. Muscles are controlled by the
nervous system. - Nervessendmessagestothemuscularsystemfromthebrain. Nervesalsosendmessages
to the brain from the muscles. Regular exercise improves the health of the muscular
system. Muscles that are exercised are bigger and stronger than muscles that are not
exercised. - Exercise improves both muscular strength and muscular endurance. Muscular strength
is the ability of a muscle to exert force during a contraction. Muscular endurance is
the ability of a muscle to continue to contract over a long time without getting tired.
Identify two types of injuries to the muscular system. - A strain is an injury to a muscle in which the muscle fibers tear because the muscle
contracts too much or contracts before the muscle is warmed up. Tiny tears and
swelling in a tendon results in tendinitis.
Review Questions
- Name the three types of muscle tissue in the body.
- Which of the three types of muscles in the body are voluntary?
- What is another name for muscle cells?
- Describe how skeletal muscles and bones work together to move the body.
- What is a tendon?
- How does aerobic exercise affect the heart?
- How does aerobic exercise affect skeletal muscle?
- How does anaerobic exercise affect skeletal muscle?
- What is a muscle strain?