MCQ on Muscle Physiology Questions and Answers

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1. The muscle protein, which covers the active sites on the actin filament at rest, is:
a. Troponin-I
b. Troponin-C
c. Tropomyosin
d. Myosin
e. Actinin
Correct answer: (c) Tropomyosin

2. During skeletal muscle contraction, there is shortening of:
a. Actin filaments
b. A-band
c. Myosin
d. Sarcomere
e. Z-disc
Correct answer: (d) Sarcomere

3. The visceral smooth muscle:
a. Is found in the iris of eye
b. Has contact type of neuromuscular junctions
c. Control is mainly through nervous stimuli
d. Is composed of individual muscle fibers
e. Shows contraction when it is stretched
Correct answer: (e) Shows contraction when stretched

4. A skeletal muscle fiber
a. Membrane is negatively charged on the inside with respect to the outside at rest.
b. Contains intracellular stores of calcium ions.
c. Is normally innervated by more than one motor neuron.
d. Becomes more excitable as its resting membrane potential falls.
e. Becomes less excitable as the extracellular ionized calcium levels fall.
ans
A. True
B. True
C. False
D. True
E. False

5. In skeletal muscle
A. Contraction occurs when its pacemaker cells depolarize sufficiently to reach the threshold for firing.
B. Calcium is taken up by the sarco-tubular system when it contracts.
C. Actin and myosin filaments shorten when it contracts.
D. The sarcomeres shorten during contraction.
E. Contraction strength is related to initial length of the muscle fibers.
ans
A. False
B. False
C. False
D. True
E. True

6. Visceral smooth muscle differs from skeletal muscle in that
A. It contracts when stretched.
B. It is not paralyzed when its motor nerve supply is cut.
C. Its cells have unstable resting membrane potentials.
D. It contains no actin or myosin.
E. Excitation depends more on influx of extracellular calcium than release of calcium from endoplasmic reticulum.
ans
A. True
B. True
C. True
D. False
E. True

7. A property shared by
A. Skeletal and cardiac muscle is their striated microscopical appearance.
B. Skeletal and multiunit smooth muscle is that they are paralyzed when their motor nerves are cut.
C. Cardiac and visceral smooth muscle is their spontaneous activity when denervated.
D. Skeletal and cardiac ventricular muscle is their stable resting membrane potential.
E. All varieties of muscle is that contraction strength is related to their initial length.
ans
A. True
B. True
C. True
D. True
E. True

8. Histological and physiological study of skeletal muscle shows that the
A. Distance between two Z lines remains constant during contraction.
B. Width of the anisotropic A band is constant during contraction.
C. Tension developed is maximal when actin and myosin molecules just fail to overlap.
D. Stimulus needed to cause contraction is minimal when applied at the Z line.
E. The T system of transverse tubules opens into the terminal cisterns of the sarcoplasmic reticulum.
ans
A. False
B. True
C. False
D. True
E. False

9. Muscle tone is reduced by
A. Curare-like drugs
B. Lower motor neuron lesions.
C. Upper motor neuron lesions
D. Cerebellar lesions
E. Gamma efferent impulses to muscle spindles
ans
A. True
B. True
C. False
D. True
E. False

10. Disease of the extrapyramidal motor system in Parkinsonism causes
A. Tremor, which is more obvious when the patient is performing skilled movements
B. Muscle paralysis
C. Increased muscle tone throughout the range of passive movement.
D. Increased involuntary facial movements during speech
E. An unusual gait with small fast regular steps
ans
A. False
B. False
C. True
D. False
E. True

11. Characteristic features of cerebellar disease include loss of
A. Muscle tone
B. Muscle strength
C. Conscious muscle-joint sense
D. Ability to make precise muscle movements
E. Ability to fix the gaze steadily on an object
ans
A. True
B. False
C. False
D. True
E. True

12. Which of the following statements concerning the structure of muscle tissue is correct?
a) Skeletal muscle has the same structure as cardiac muscle
b) Smooth muscle cells have no striations as they lack myosin filaments
c) Smooth muscle has a system of T-tubules.
d) The myofibrils of skeletal muscle are surrounded by the sarcoplasmic reticulum.
ans
d) The myofibrils of skeletal muscle are surrounded by the sarcoplasmic reticulum.

13. Which of the following statements concerning the role of Ca2+ in the contraction of skeletal muscle is correct?
a) The mitochondria act as a store of Ca2+ for the contractile process
b) Ca2+ entry across the plasma membrane is important in sustaining the contraction of skeletal muscle
c) A rise in intracellular Ca2+allows actin to interact with myosin
d) The tension of a skeletal muscle fiber is partly regulated by G proteins.
ans
c) A rise in intracellular Ca2+allows actin to interact with myosin

14. Which of the following statements concerning cardiac muscle is correct?
a) The force of contraction is increased by circulating adrenaline
b) Heart muscle contracts in response to action potentials in the autonomic nerve fibers
c) The action potential has the same duration as that of skeletal muscle
d) All of the Ca2+required for contraction enters a myocyte during the plateau phase of the action potential
ans
a) The force of contraction is increased by circulating adrenaline

15. The maximum power that can be developed by a skeletal muscle [Select all that apply]
a) Is independent of the initial length of the muscle
b) Occurs with an isometric contraction
c) Occurs when the muscle is moving a load at about one third of its maximum rate of shortening
d) Occurs when the muscle is shortening at its maximum rate
e) Depends on the load being moved by the muscle
ans
c) Occurs when the muscle is moving a load at about one third of its maximum rate of shortening
e) Depends on the load being moved by the muscle

16. Which of the following statements concerning the contraction of smooth muscle is/are correct? [Select all that apply]
a) Individual muscle fibers are innervated by autonomic nerves
b) All smooth muscles behave as a single motor unit
c) Some smooth muscles may contract without an action potential
d) Although smooth muscle is innervated by autonomic nerves there is no specific neuromuscular junction
e) The contraction of smooth muscle is regulated by calcium in the same manner as cardiac muscle.
ans
c) Some smooth muscles may contract without an action potential
d) Although smooth muscle is innervated by autonomic nerves there is no specific neuromuscular junction

17. Skeletal muscle has a system of T-tubules while smooth muscle does not. True or false?
a) True
b) False
ans
a) True

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