Page 418 - Fundamentals of anatomy physiology
P. 418
Chapter 11 The Muscular System 405
Checkpoint The Ability to Recover from Muscular Injuries Decreases. The
18. Shrugging your shoulders uses which muscles? number of satellite cells steadily decreases with age, and
1 9. Baseball pitchers sometimes suffer from rotator cuff the amount of fibrous tissue increases. As a result, when an
injury occurs, repair capabilities are limited. Scar tissue for-
injuries. Which muscles are involved in this type of mation is the usual result.
injury?
2 0. An injury to the flexor carpi ulnaris muscle would Regular exercise helps control body weight, strengthens
impair which two movements? bones, and generally improves the quality of life at all ages.
2 1. Which leg movement would be impaired by injury to Extremely demanding exercise is not as important as regular
the obturator muscle? exercise. In fact, extreme exercise in the elderly can damage
22. To what does a “pulled hamstring” refer? tendons, bones, and joints.
2 3. How would a torn calcaneal tendon affect movement of
the foot? Checkpoint 11
See the blue Answers tab at the back of the book. 2 4. Describe general age-related effects on skeletal muscle
tissue.
11-7 With advancing age, the size
25. Define fibrosis.
and power of muscle tissue decrease
See the blue Answers tab at the back of the book.
Learning Outcome Identify age-related changes of the muscular
system. 11-8 Exercise produces responses
We can summarize the effects of aging on the muscular system in multiple body systems
as follows:
Learning Outcome Explain the functional relationship between the
Skeletal Muscle Fibers Become Smaller in Diameter. This re- muscular system and other body systems, and explain the role of exercise
in producing various responses in other body systems.
duction in size reflects a decrease in the number of myo-
fibrils. In addition, the muscle fibers contain smaller ATP, To operate at maximum efficiency, the muscular system must
CP, and glycogen reserves and less myoglobin. The overall be supported by many other systems. The changes that take
effect is a reduction in skeletal muscle size, strength, and place during exercise provide a good example of such interac-
endurance, combined with a tendency to fatigue quickly. tion. As noted earlier, active muscles consume oxygen and gen-
Because cardiovascular performance also decreases with erate carbon dioxide and heat. The immediate effects of exercise
age, blood flow to active muscles does not increase with ex- on various body systems include the following:
ercise as rapidly as it does in younger people. These factors
interact to produce decreases of 30–50 percent in anaero- Cardiovascular System: Blood vessels in active muscles and
bic and aerobic performance by age 65.
the skin dilate, and heart rate increases. These adjustments
Skeletal Muscles Become Less Elastic. Aging skeletal muscles speed up oxygen and nutrient delivery to and carbon diox-
ide removal from the muscle. They also bring heat to the
develop increasing amounts of fibrous connective tissue, skin for radiation into the environment.
a process called fibrosis. Fibrosis makes the muscle less
flexible, and the collagen fibers can restrict movement and Respiratory System: Respiratory rate and depth of respiration
circulation.
increase. Air moves into and out of the lungs more quickly,
Tolerance for Exercise Decreases. A lower tolerance for exercise keeping pace with the increased rate of blood flow through
the lungs.
comes in part from tiring quickly and in part from reduced
thermoregulation, described in Chapter 5. p. 194 Integumentary System: Blood vessels dilate, and sweat gland
Individuals over age 65 cannot eliminate the heat their
muscles generate during contraction as effectively as younger secretion increases. This combination increases evaporation
people can. For this reason, they are subject to overheating. at the skin surface and removes the excess heat generated
by muscular activity.
