Muscles by yaoyufang






Instructions: Read pages 590-596 and answer the following questions.

1. How many muscles are present in the human body?
more than 600

2. Define skeletal muscle--
Muscle that is attached to the bones of the skeleton; skeletal muscle tissue is
voluntary muscle.

3. What is another name for skeletal muscles?
voluntary muscles

4. Define smooth muscle--
muscle not usually under conscious control

5. How is smooth muscle different than skeletal muscle?
You have control over your skeletal muscle, but smooth muscle is not under your

6. Explain two examples of smooth muscles at work in the human body.
Smooth muscles work to reduce the diameter of blood vessels in your skin on a
cold day. Smooth muscles in your eye cause your pupils to become smaller so
that you will not be blinded by the bright sunshine. Smooth muscles are also
found in the walls of internal organs such as those in your digestive system,
where they move food through your body.

7. How is cardiac muscle different from both skeletal muscle and smooth
Cardiac muscle cells are self-starters. They cause themselves to contract by
generating their own electrical signals. Skeletal and smooth muscle must receive
an electrical impulse from a nerve to contract.

8. True or False    Muscles can push and pull bones. False, only pull.

9. Why are two sets of muscles required to move a bone?
When a muscle pulls on a bone, it moves the bone in one direction. Because the
muscle cannot push on the bone, another muscle is needed to pull the bone in
the opposite direction.

10. What could possibly happen if both sets of muscles of a particular bone
contracted and shortened at the same time?

The bone wouldn’t move because the muscles would be pulling in opposite
directions. However, large muscles in your legs are so powerful that if all of the
muscles contracted strongly at the same time, they could break a bone.

11. What does your body do in order to help prevent two sets of muscles from
contracting and shortening at the same time?

A nerve message is sent from one set of muscles to the other. When one set
contracts, the other set is signaled to relax.

12. What type of tissue make up ligaments and tendons?

Tough, elastic connective tissue

13. What is the difference between ligaments and tendons?

Ligaments attach bones to bone, and tendons attach muscles to bone.

14. What determines the amount of force in a muscle contraction?

The amount of force is determined by the signals from the nervous system that
make more or less force by contracting more or less muscle cells.

15. Explain what muscle tone is.

Even when you are not moving, your nervous system constantly sends signals to
some of the muscle cells in all of your muscles. As one set of cells tires, signals
are sent to another set so your skeletal muscles are always partly contracted.
This constant, partial contraction of your muscles is known as muscle tone.

16. What happens to muscles if they are not used over a long period of time?
Muscles that are not used fatigue easily and over time they harden, become
smaller, and lose strength.

17. Define aerobic exercise--
continuous, low or moderate intensity exercise that ensures that your lungs and
heart can deliver oxygen to your muscles at the same rate at which the muscle
cells are using it. Your muscles can use this continuous supply of oxygen to
extract the maximum amount of energy from food molecules and to continue the
activity for as long as 20 minutes or more.

18. What does aerobic exercise do for the body?

Aerobic training makes the heart stronger and enables it to pump more blood in
fewer beats. It strengthens the lungs and diaphragm thus allowing more air for
each breath; it increases the number of capillaries in the muscles and the
number of mitochondria in muscle cells. This increased ability to supply oxygen
to the muscles results in increased endurance, the ability to keep going longer.
Aerobic training increases blood flow to all working muscles in any kind of

19. How is anaerobic exercise different from aerobic exercise?

Anaerobic exercise is exercise that is short and intense. Because of its intensity,
it requires a large amount of energy. With anaerobic exercise, energy is used
faster than it can be converted. Your body cannot take in enough oxygen to
convert glucose into ATP; instead, glucose is turned into lactic acid. Lactic acid
causes your muscles to tire quickly. Aerobic exercise is a continuous, low or
moderate intensity exercise that ensures that your lungs and heart can deliver
oxygen to your muscles at the same rate at which the muscle cells are using it.

20. Explain the benefits of resistance exercise.

Resistance exercise increases the size, strength, and endurance of your skeletal
muscles. It also helps to increase bone mass.

21. Why are some people better at sprinting, jumping, and weight lifting?

There are two different types of muscle cells—fast twitch and slow twitch. Fast
twitch muscle cells are used for speed and quick movements over a short period.
Slow twitch muscle cells respond more slowly but do not tire as quickly as fast
twitch muscle cells. Some people are born with more fast twitch muscles cells
and vice versa. Sprinters, jumpers, and weight lifters have more fast twitch
muscle cells than slow twitch.

22. Explain why a muscle will not work as well as it once did after an injury.
Muscle is made up of collagen and elastin fibers. Elastin stretches, collagen does
not. When a muscle heals after a tear, its elastin is replaced by collagen. The
muscle doesn’t stretch as well.

23. Now, read page 181 of your anatomy/physiology book. After reading, list
three reasons why you wouldn’t take steroids.

In males, they can cause female looking breasts to form and decreased sperm
production leading to possible sterility.

In females, the voice deepens, and the girl will develop an overall more male

In both sexes, there is a greater chance of kidney, liver, and heart damage.
Steroids also raise bad cholesterol leading to increased plaque deposition in the
blood vessels. Steriods stunt your growth and may lead to early baldness. Both
sexes will experience increased aggression and mood swings and severe acne is
more common. Tendons and ligaments can tear due to increased muscle growth.

24. Now, read the Topic of Interest on page 183 of your anatomy/physiology
book. After reading, answer the following.

a. How can you remember that hypertrophy means to “bulk up” muscle and
atrophy means to shrink muscle tissue?

Hyper means above. So a muscle that experiences hypertrophy would be above
average size. A means without. So a muscle that has atrophied would be below
normal size.

b. If you were jogging, which would you be relying on—slow fibers or fast fibers?

Slow twitch fibers

25. Now, read page 186 of your anatomy/physiology book. After reading, answer
the following.

a. Why do people who have Duchenne muscular dystrophy usually pass away?

A person with Duchenne muscular dystrophy usually dies in early adulthood due
to not being able to breath because of failed respiratory muscles.

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