Ch. 10 Muscle Tissue Flashcards
Muscle that has a striped appearance is described as being (BLANK).
A) Elastic.
B) Nonstriated.
C) Excitable.
D) Striated.
D) Striated.
Explanation: Striated muscle (skeletal and cardiac) shows visible stripes under a microscope due to the arrangement of actin and myosin filaments.
Incorrect: A) Elastic – Refers to flexibility, not appearance. B) Nonstriated – Refers to smooth muscle, which lacks stripes. C) Excitable – Describes responsiveness, not visual features.
Which element is important in directly triggering contraction?
A) Sodium (Na⁺).
B) Calcium (Ca²⁺).
C) Potassium (K⁺).
D) Chloride (Cl⁻).
B) Calcium (Ca²⁺).
Explanation: Calcium binds to regulatory proteins, initiating the contraction process by allowing myosin to interact with actin.
Incorrect: A) Sodium initiates the action potential but doesn’t trigger contraction directly. C) Potassium is involved in repolarization, not initiating contraction. D) Chloride plays a minor role in electrical balance, not in contraction.
Which of the following properties is not common to all three muscle tissues?
A) Excitability.
B) The need for ATP.
C) At rest, uses shielding proteins to cover actin-binding sites.
D) Elasticity.
C) At rest, uses shielding proteins to cover actin-binding sites.
Explanation: Only skeletal and cardiac muscles use troponin and tropomyosin to block actin binding sites. Smooth muscle uses a different calcium-activated mechanism.
Incorrect: A) Excitability is shared by all muscle types. B) ATP is required by all three for contraction. D) Elasticity is a shared property allowing muscles to return to their original shape.
The correct order from the smallest to the largest unit of organization in muscle tissue is (BLANK).
A) Fascicle, Filament, Muscle Fiber, Myofibril.
B) Filament, Myofibril, Muscle Fiber, Fascicle.
C) Muscle Fiber, Fascicle, Filament, Myofibril.
D) Myofibril, Muscle Fiber, Filament, Fascicle.
B) Filament, Myofibril, Muscle Fiber, Fascicle.
Explanation: This order reflects muscle tissue organization: actin/myosin filaments make up myofibrils, which are found in a muscle fiber, and fibers are grouped into fascicles.
Incorrect: A), C), and D) mix up the correct size-based hierarchy.
- The cell membrane of a muscle fiber is called (BLANK).
A) Myofibril.
B) Sarcolemma.
C) Sarcoplasm.
D) Myofilament.
B) Sarcolemma.
Explanation: The sarcolemma is the plasma membrane of a skeletal muscle fiber.
Incorrect: A) Myofibril – Bundle of contractile proteins inside the fiber. C) Sarcoplasm – The cytoplasm of the muscle cell. D) Myofilament – Refers to actin and myosin proteins inside myofibrils.
Depolarization of the sarcolemma means (BLANK).
A) The inside of the membrane has become less negative as sodium ions accumulate.
B) The outside of the membrane has become less negative as sodium ions accumulate.
C) The inside of the membrane has become more negative as sodium ions accumulate.
D) The sarcolemma has completely lost any electrical charge.
A) The inside of the membrane has become less negative as sodium ions accumulate.
Explanation: Depolarization occurs when Sodium rushes into the cell, making the inside less negative (more positive).
Incorrect:
B) The outside doesn’t become less negative.
C) More negative inside would be hyperpolarization.
D) The sarcolemma never loses all charge—this is physiologically incorrect.
In relaxed muscle, the myosin-binding site on actin is blocked by (BLANK).
A) Titin.
B) Troponin.
C) Myoglobin.
D) Tropomyosin.
D) Tropomyosin.
Explanation: Tropomyosin blocks myosin-binding sites on actin until calcium binds to troponin, moving tropomyosin aside.
Incorrect:
A) Titin is for structural elasticity, not regulation.
B) Troponin holds tropomyosin in place, but doesn’t block the site itself.
C) Myoglobin stores oxygen in muscle cells and doesn’t regulate contraction.
According to the sliding filament model, binding sites on actin open when (BLANK).
A) Creatine phosphate levels rise.
B) ATP levels rise.
C) Acetylcholine levels rise.
D) Calcium ion levels rise.
D) Calcium ion levels rise.
Explanation: Calcium binds to troponin, which shifts tropomyosin and reveals binding sites on actin.
Incorrect:
A) Creatine phosphate is for ATP regeneration, not binding site exposure.
B) ATP is necessary for contraction but doesn’t expose binding sites.
C) Acetylcholine initiates the signal, not the physical exposure of actin sites.
Muscle relaxation occurs when (BLANK).
A) Calcium ions are actively transported out of the sarcoplasmic reticulum.
B) Calcium ions diffuse out of the sarcoplasmic reticulum.
C) Calcium ions are actively transported into the sarcoplasmic reticulum.
D) Calcium ions diffuse into the sarcoplasmic reticulum.
C) Calcium ions are actively transported into the sarcoplasmic reticulum.
Explanation: Relaxation requires ATP-powered pumps to actively move Ca²⁺ back into the sarcoplasmic reticulum (SR).
Incorrect:
A) and B) – Ions must return into the SR, not out.
D) Diffusion is passive; Ca²⁺ reuptake is active.
- During muscle contraction, the cross-bridge detaches when (BLANK).
A) The myosin head binds to an ADP molecule.
B) The myosin head binds to an ATP molecule.
C) Calcium ions bind to troponin.
D) Calcium ions bind to actin.
B) The myosin head binds to an ATP molecule.
Explanation: ATP binding to myosin causes the release of myosin from actin, ending the power stroke.
Incorrect:
A) ADP is released during the power stroke, not detachment.
C) & D) – Calcium binding initiates contraction, not detachment.
- Thin and thick filaments are organized into functional units called (BLANK).
A) Myofibrils.
B) Myofilaments.
C) T-tubules.
D) Sarcomeres.
D) Sarcomeres.
Explanation: A sarcomere is the smallest contractile unit of a muscle fiber, composed of organized actin and myosin filaments.
Incorrect:
A) Myofibrils contain many sarcomeres.
B) Myofilaments are individual proteins within sarcomeres.
C) T-tubules conduct electrical signals, not contractile units.
During which phase of a twitch in a muscle fiber is tension the greatest?
A) Resting phase.
B) Repolarization phase.
C) Contraction phase.
D) Relaxation phase.
C) Contraction phase.
Explanation: Tension peaks during the contraction phase, when cross-bridges are actively pulling on actin.
Incorrect:
A) Resting – No activity.
B) Repolarization – Term isn’t typically used in muscle twitch context.
D) Relaxation – Tension decreases as Calcium is reabsorbed.
Muscle fatigue is caused by (BLANK).
A) Buildup of ATP and lactic acid levels.
B) Exhaustion of energy reserves and buildup of lactic acid levels.
C) Buildup of ATP and pyruvic acid levels.
D) Exhaustion of energy reserves and buildup of pyruvic acid levels.
B) Exhaustion of energy reserves and buildup of lactic acid levels.
Explanation: Fatigue occurs when ATP runs low and lactic acid accumulates, especially during anaerobic metabolism.
Incorrect:
A & C) ATP buildup doesn’t happen; it’s rapidly used.
D) Pyruvic acid is not the primary fatigue-causing agent.
A sprinter would experience muscle fatigue sooner than a marathon runner due to (BLANK).
A) Anaerobic metabolism in the muscles of the sprinter.
B) Anaerobic metabolism in the muscles of the marathon runner.
C) Aerobic metabolism in the muscles of the sprinter.
D) Glycolysis in the muscles of the marathon runner.
A) Anaerobic metabolism in the muscles of the sprinter.
Explanation: Sprinters use fast glycolytic (FG) fibers, which rely on anaerobic metabolism that fatigues quickly.
Incorrect:
B) Marathon runners rely on aerobic metabolism.
C) Sprinters don’t primarily use aerobic systems.
D) Glycolysis does occur but isn’t the dominant system in marathon runners.
What aspect of creatine phosphate allows it to supply energy to muscles?
A) ATPase activity.
B) Phosphate bonds.
C) Carbon bonds.
D) Hydrogen bonds.
B) Phosphate bonds.
Explanation: Creatine phosphate donates high-energy phosphate to ADP to regenerate ATP during early muscle contraction.
Incorrect:
A) ATPase is an enzyme, not a creatine phosphate feature.
C & D) Carbon and hydrogen bonds are not the main energy source here.
Drug X blocks ATP regeneration from ADP and phosphate. How will muscle cells respond to this drug?
A) By absorbing ATP from the bloodstream.
B) By using ADP as an energy source.
C) By using glycogen as an energy source.
D) None of the above.
D) None of the above.
Explanation: Muscle cells cannot absorb ATP directly, ADP is not a usable fuel, and glycogen use still requires ATP regeneration, which is blocked by the drug.
Incorrect: A–C all require or assume ATP regeneration is possible, which it isn’t in this scenario.
The muscles of a professional sprinter are most likely to have (BLANK).
A) 80 percent fast-twitch muscle fibers and 20 percent slow-twitch muscle fibers.
B) 20 percent fast-twitch muscle fibers and 80 percent slow-twitch muscle fibers.
C) 50 percent fast-twitch muscle fibers and 50 percent slow-twitch muscle fibers.
D) 40 percent fast-twitch muscle fibers and 60 percent slow-twitch muscle fibers.
A) 80 percent fast-twitch muscle fibers and 20 percent slow-twitch muscle fibers.
Explanation: Sprinters rely on fast glycolytic fibers for quick, powerful contractions—typically dominating their muscle composition.
Incorrect: B–D underrepresent fast-twitch fibers for a power/sprint athlete.
The muscles of a professional marathon runner are most likely to have (BLANK).
A) 80 percent fast-twitch muscle fibers and 20 percent slow-twitch muscle fibers.
B) 20 percent fast-twitch muscle fibers and 80 percent slow-twitch muscle fibers.
C) 50 percent fast-twitch muscle fibers and 50 percent slow-twitch muscle fibers.
D) 40 percent fast-twitch muscle fibers and 60 percent slow-twitch muscle fibers.
B) 20 percent fast-twitch muscle fibers and 80 percent slow-twitch muscle fibers.
Explanation: Marathon runners rely heavily on slow oxidative (SO) fibers, which are fatigue-resistant and optimized for endurance.
Incorrect: A), C), D) underrepresent the endurance-enhancing slow-twitch fibers dominant in marathon athletes.
Which of the following statements is true?
A) Fast fibers have a small diameter.
B) Fast fibers contain loosely packed myofibrils.
C) Fast fibers have large glycogen reserves.
D) Fast fibers have many mitochondria.
C) Fast fibers have large glycogen reserves.
Explanation: Fast glycolytic (FG) fibers use anaerobic metabolism and store large glycogen reserves for quick energy.
Incorrect:
A) They have a large, not small, diameter.
B) Their myofibrils are densely, not loosely, packed.
D) They have few, not many, mitochondria.
Which of the following statements is false?
A) Slow fibers have a small network of capillaries.
B) Slow fibers contain the pigment myoglobin.
C) Slow fibers contain a large number of mitochondria.
D) Slow fibers contract for extended periods.
A) Slow fibers have a small network of capillaries.
Explanation: This is false—slow oxidative fibers have an extensive capillary network to support aerobic metabolism.
Incorrect: B), C), and D) are all true and describe slow-twitch muscle fibers accurately.
Cardiac muscles differ from skeletal muscles in that they (BLANK).
A) Are striated.
B) Utilize aerobic metabolism.
C) Contain myofibrils.
D) Contain intercalated discs.
D) Contain intercalated discs.
Explanation: Cardiac muscle is unique in that its fibers are connected by intercalated discs, which include gap junctions and desmosomes for unified contractions.
Incorrect: A), B), C) are shared characteristics with skeletal muscle.
If cardiac muscle cells were prevented from undergoing aerobic metabolism, they ultimately would (BLANK).
A) Undergo glycolysis.
B) Synthesize ATP.
C) Stop contracting.
D) Start contracting.
C) Stop contracting.
Explanation: Cardiac muscle relies almost entirely on aerobic metabolism. Without it, ATP levels would drop and contraction would cease.
Incorrect:
A) Glycolysis provides insufficient ATP for cardiac function.
B) ATP synthesis would halt without aerobic metabolism.
D) ‘Start contracting’ is unrelated to loss of oxygen.
Smooth muscles differ from skeletal and cardiac muscles in that they (BLANK).
A) Lack myofibrils.
B) Are under voluntary control.
C) Lack myosin.
D) Lack actin.
A) Lack myofibrils.
Explanation: Smooth muscle cells lack myofibrils and sarcomeres, giving them a non-striated appearance.
Incorrect:
B) They are involuntary, not voluntary.
C & D) Smooth muscle does have both actin and myosin.
Which of the following statements describes smooth muscle cells?
A) They are resistant to fatigue.
B) They have a rapid onset of contractions.
C) They cannot exhibit tetanus.
D) They primarily use anaerobic metabolism.
A) They are resistant to fatigue.
Explanation: Smooth muscle contracts slowly and efficiently, making it fatigue-resistant.
Incorrect:
B) Their contractions are slow to begin.
C) They can show sustained contractions (especially in visceral smooth muscle).
D) They primarily rely on aerobic metabolism.
