muscles bones and movement

smooth muscles and cardiac muscles

Smooth muscles and cardiac muscles are not attached to bone. Recall that these types of muscles are under involuntary control. Smooth muscle is responsible for the contractility of hollow organs, such as blood vessels, the gastrointestinal tract, the bladder, or the uterus. Like skeletal muscles, smooth muscle fibers do contract together, causing the muscle to shorten. Smooth muscles have numerous functions, including the following. The smooth muscle in the uterus helps a woman to push out her baby. In the bladder, smooth muscle helps to push out urine. Smooth muscles move food through the digestive tract. In arteries, smooth muscle movements maintain the arteries diameter. Smooth muscle regulates air flow in lungs. Smooth muscle in the lungs helps the airways to expand and contract as necessary. Smooth muscles in arteries and veins are largely responsible for regulation of blood pressure. Cardiac muscle also contracts and gets shorter. This muscle is found only in the heart. The sudden burst of contraction forces blood throughout your body. When the cardiac muscle relaxes, the heart fills with blood. This rhythmic contraction must continue for your whole life, luckily the heart muscle never gets tired. If your heart beats 75 times a minute, how many times does it beat in an hour? A day? A year? 85 years?

muscles bones and movement

When skeletal muscles contract, bones move. But how do muscles make your bones move? A voluntary muscles usually works across a joint. It is attached to both the bones on either side of the joint by strong cords called tendons. A tendon is a tough band of connective tissue that connects a muscle to a bone. Tendons are similar to ligaments, except that ligaments join bones to each other. Muscles move the body by contracting against the skeleton. When muscles contract, they get shorter. By contracting, muscles pull on bones and allow the body to move. Muscles can only contract. They cannot actively extend, though they can move or relax back into the non-contracted neutral position. Therefore, to move bones in opposite directions, pairs of muscles must work in opposition. Each muscle in the pair works against the other to move bones at the joints of the body. The muscle that contracts to cause a joint to bend is called the flexor. The muscle that contracts to cause the joint to straighten is called the extensor. When one muscle is contracted, the other muscle from the pair is always elongated. For example, the biceps and triceps muscles work together to allow you to bend and straighten your elbow. When you want to bend your elbow, your biceps muscle contracts (Figure 1.1), and, at the same time, the triceps muscle relaxes. The biceps is the flexor, and the triceps is the extensor of your elbow joint. Other muscles that work together are the quadriceps and hamstrings used to bend and straighten the knee, and the pectorals and trapezius used to move the arms and shoulders forward and backward. During daily routines we do not use muscles equally. For example, we use our biceps more than our triceps due to lifting against gravity.


instructional diagrams

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when smooth muscles contract, bones move.

a. true

-->  b. false

tendons join two bones to each other.

a. true

-->  b. false

the biceps work together with the

a) pectorals.

-->  b) triceps.

c) quadriceps.

d) muscles.

which muscles are used to move the arms forward and backward?

a) quadriceps and pectorals.

b) biceps and triceps.

-->  c) pectorals and trapezius.

d) biceps and pectorals.

which muscles are used to bend the knee?

-->  a) quadriceps and hamstrings

b) pectorals and trapezius

c) hamstrings and trapezius

d) quadriceps and pectorals

if your heart contracts 75 times a minute, how many times does it contract each day?

a) about 2,000

b) about 10,000

-->  c) slightly over 100,000

d) about 1,000,000

which of the following are functions of smooth muscle?

a) helps a woman to push out her baby

b) regulates air flow in lungs

c) move food through the digestive tract

-->  d) all of the above

diagram questions

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