541. Resting membrane potential of skeletal muscle is about:
A. +90mV
B. +30mV
C. OmV
D. -3 0mV
E. -90mV
542. Absolute refractory period in the skeletal muscle is:
A. 1-3 ms
B. 3-6 ms
C. 6-9 ms
D. 9-12 ms
E. 12-15 ms
543. During skeletal muscle fiber contraction:
A. Z lines are brought closer to each other
B. A band remain constant
C. I zone shortens
D. Length of filament remains unchanged
E. All of the above
544. Which of the following statement regarding skeletal muscle contraction is FALSE?
A. Actin contains ATPase which produce s energy for sliding filament mechanisms
B. Troponin has binding sites for calcium, actin & tropomyosin
C. Myosin head is covered by tropomyosin in the resting state, so to prevent actin binding
D. Calcium is a crucial ion in triggering the power stroke mechanism.
E. All of the above
545. Which of the following statement regarding summation of contraction is FALSE?
A. Summation of contraction occurs with repeated stimulation of the muscle.
B. Complete tetanus means there is no relaxation between individual stimuli to the muscle fiber.
C. Incomplete tetanus means there is incomplete relaxation between individual stimuli to the muscle fiber.
D. Refractory period of muscle contraction is about 3 ms
E. Treppe occurs with maximal stimuli delivered to the muscle at subtetanizing threshold.
546. Which of the following statement regarding the properties of skeletal muscle contraction is INCORRECT?
A. Active tension of a muscle fiber is maximal at its resting length
B. Total tension of a muscle fiber decreases with increasing stretch of the fiber.
C. Shortening of sarcomere decreases total tension in the muscle
D. Velocity of contraction is maximal at high workload
E. All of the above
547. Fast muscle fiber:
A. mainly uses aerobic glycolysis
B. is specialized in posture maintaining contractions
C. It’s sarcoplasmic reticulum has high calcium pumping capacity
D. Is also called red muscle
E. Is usually of moderate diameter
548. Which of the following statement regarding skeletal muscle metabolism is TRUE?
A. Phosphoryl creatinine provide important source of organic phosphate to muscle
B. Source of A TP for muscle at rest is provided by fatty acid breakdown
C. During exercise, glucose is the predominant energy source to muscle
D. Anaerobic glycolysis is only capable of producing 111 0 amount of A TP produced by aerobic glycolysis per glucose molecule
E. All of the above
549. Effect of skeletal muscle denervation includes the following EXCEPT:
A. skeletal muscle atrophy
B. fasciculation
C. abnormal excitability of muscle
D. increased sensation to circulating ACh
E. Fibrillation
550. Which of the following statement regarding motor units is FALSE?
A. The size motor units are uniform
B. Each spinal motor nucleus only innervate 1 kind of muscle fiber
C. Slow motor unit is supplied by small sized motor nerve
D. Fast motor unit is supplied by larger sized motor nerve
E. Ultimate determinant of whether a motor unit is fast or slow is more determined by the nerve supply than muscle fiber type.