Self Quiz

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 muscle cells are depolarized by stretching.

2. Fast-twitch fibers differ from slow-twitch fibers in that a. they are more common in the leg muscles of champion sprinters.

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 the leg muscles of champion cross-country skiers.

3. The role of Ca2+ 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.

4. Fifteen minutes into a 10-km run, what is the major energy source of the leg muscules?

a. Preformed ATP

b. Glycolysis c. Oxidative metabolism d. Pyruvate and lactate e. High-protein drink consumed right before the race

5. Which statement about muscle contractions 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 Ca2+ 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.

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.

7. 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 very high density of osteoclasts.

e. they consist of lightweight cancellous bone with an internal meshwork of supporting elements.

8. If we compare the jaw joint with the knee joint 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 arm.

e. only the jaw is a hinged joint.

9. Which statement about skeletons is true?

a. They can consist of mostly cartilage.

b. Hydrostatic skeletons can be used only for amoeboid motion.

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.

10. Which of the following effectors is not used both for avoiding predators and for communication?

a. Chromatophores b. Nematocysts c. Electric organs d. Skeletal muscle e. Pheromones

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Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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