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Example Questions
Example Question #11 : Muscle Physiology
The sliding filament theory of muscle contraction involves the __________ attaching to __________ and then pulling during the power stroke.
actin head . . . myosin
myosin head . . . actin
troponin . . . actin
myosin . . . tropomyosin
myosin head . . . actin
The sliding filament theory of muscle contraction involves the myosin head attaching to actin and then pulling during the power stroke. Troponin is a protein attached to tropomyosin, a thin strand wrapping around the actin filament. When calcium enters the cell, troponin moves toward it, pulling the tropomyosin strand away from actin binding sites and allowing the myosin head to bind.
Example Question #61 : Musculoskeletal System And Anatomy
Which of the following molecules binds to troponin during muscle contraction, triggering tropomyosin to move away from the actin binding sites and allowing the myosin head to form a cross bridge?
Sodium
Calcium
ATP
ADP
Calcium
During a muscle cell action potential, calcium enters the cell via t-tubules, which are specialized invaginations of the sarcoplasmic reticulum. Calcium binds with troponin, which pulls the tropomyosin strand away from actin binding sites and allows myosin heads to bind. Neither sodium nor potassium bind to troponin, and ATP and ADP both bind to myosin, rather than troponin.
Example Question #62 : Musculoskeletal System And Anatomy
Which of the following is the name of the modified endoplasmic reticulum found in muscle cells?
The sarcomere
The myoplasmic reticulum
The sarcoplasmic reticulum
The t-tubule
The sarcoplasmic reticulum
Muscle cells have a specialized endoplasmic reticulum called the sarcoplasmic reticulum. The sarcoplasmic reticulum regulates the calcium ion concentration in the cytoplasm of striated muscle cells, and so plays a significant role in muscle contraction and relaxation. The T-tubule is a specialized invagination of the sarcoplasmic reticulum, and the sarcomere is the single contractile unit of a muscle fibril. There is no muscle structure called the mycoplasmic reticulum.
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