Life: The Science of Biology

David E. Sadava, David M. Hilliss, H. Craig Heller,May Berenbaum

Chapter 48

Musculoskeletal Systems - all with Video Answers

Educators

Chapter Questions

Problem 1

Smooth muscle differs from both cardiac and skeletal muscle in that
$a$ it can act as a pacemaker for rhythmic contractions.
b. contractions of smooth muscle are not due to interactions between neighboring microfilaments.
c. neighboring cells are electrically connected by gap junctions.
$d$ neighboring cells are tightly coupled by intercalated discs.
$e$ the membranes of smooth muscie cells are depolarized by stretching.

Katie Haasch

Katie Haasch

Numerade Educator

Problem 2

Fast-twitch fibers differ from slow-twitch fibers in that
$a$. they are more common in the leg muscles of champion sprinters than marathon runners.
b. they have more mitochondria.
$c$ they fatigue less rapidly.
$d$. their abundance is more a product of training than of genetics.
e. they are more common in postural muscles than in finger muscles.

Katie Haasch

Numerade Educator

Problem 3

The role of $\mathrm{Ca}^{2+}$ in the control of muscle contraction is to
$a$. cause depolarization of the T tubule system.
b. change the conformation of troponin, thus exposing myosin-binding sites.
$c$. change the conformation of myosin heads, thus causing microfilaments to slide past each other.
$d$. bind to tropomyosin and break actin-myosin cross-bridges.
e. block the ATP-binding site on myosin heads, enabling muscles to relax.

Katie Haasch

Numerade Educator

Problem 4

Fifteen minutes into a 10 -k run, what is the major energy source of the leg muscles?
a. Preformed ATP
$b .$ Glycolysis
c. Oxidative metabolism
dyruvate and lactate
e. High-protein drink consumed right before the race.

Katie Haasch

Numerade Educator

Problem 5

Which statement about skeletal muscle contraction is not true?
a. A single action potential at the neuromuscular junction is sufficient to cause a muscle to twitch.
b. Once maximum muscle tension is achieved, no ATP is required to maintain that level of tension.
c. An action potential in the muscle cell activates contraction by releasing $\mathrm{Ca}^{2+}$ into the sarcoplasm.
$d .$ Summation of twitches leads to a graded increase in the tension that can be generated by a single muscle fiber.
e. The tension generated by a muscle can be varied by controlling how many of its motor units are active.

Christina Sorrentino

Christina Sorrentino

Numerade Educator

Problem 6

Which statement about the structure of skeletal muscle is true?
$a$. The light bands of the sarcomere are the regions where actin and myosin filaments overlap.
b. When a muscle contracts, the A bands of the sarcomere lengthen.
c. The myosin filaments are anchored in the Z lines.
d. When a muscle contracts, the H zone of the sarcomere shortens.
e. The sarcoplasm of the muscle cell is contained within the sarcoplasmic reticulum.

Bin Chen

Numerade Educator

Problem 7

Insects can beat their wings at exceptionally high frequencies because
$a$. their wing muscles have mostly fast-twitch fibers.
b. their motor neurons can fire action potentials at a very high frequency.
c. their wings have exoskeletal supports.
$d$. their wing muscles have extensive sarcoplasmic reticulum that cycles $\mathrm{Ca}^{2+}$ very fast.
$e$ their wing muscles can generate a rapid oscillation of contraction asynchronous with motor neuron firing.

Christina Sorrentino

Christina Sorrentino

Numerade Educator

Problem 8

The long bones of our arms and legs are strong and can resist both compressional and bending forces because
$a$, they are solid rods of compact bone.
$b$. their extracellular matrix contains crystals of calcium carbonate.
$c$ their extracellular matrix consists mostly of collagen and polysaccharides.
$d$. they have a high density of osteoclasts.
e. they consist of lightweight cancellous bone with an internal meshwork of supporting elements.

Katie Haasch

Numerade Educator

Problem 9

If we compare the jaw and knee joints as lever systems,
$a$ the jaw joint can apply greater compressional forces.
$b$, their ratios of power arm to load arm are about the same.
$c$. the knee joint has greater rotational abilities.
$d$. the knee joint has a greater ratio of power arm to load $\operatorname{arm}$
$e$ only the jaw is a hinged joint.

Katie Haasch

Numerade Educator

Problem 10

Which statement about skeletons is true?
$a$. They can consist of mostly cartilage.
b. Hydrostatic skeletons cannot be used for locomotion.
c. An advantage of exoskeletons is that they can continue to grow throughout the life of the animal.
d. External skeletons must remain flexible, so they never include calcium carbonate crystals, as bones do.
$e .$ Internal skeletons consist of four different types of bone:
compact, cancellous, membranous, and Haversian.

Katie Haasch

Numerade Educator