The smallest contractile unit of muscle contraction, called a sarcomere, is the area between two?
Correct answer: C. Z line
- A. H zone
- B. M line
- C. Z line
- D. Z zone
Explanation
The correct answer is the Z line. The sarcomere is the basic contractile unit of muscle fibers and is defined by the area between two Z lines. These lines serve as anchor points for actin filaments and help maintain the structure during contraction. The H zone and M line are internal components of the sarcomere that do not define its boundaries. The term 'Z zone' is not used in muscle anatomy; thus, it is not a correct option.
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About Muscle Contraction
Muscle contraction is explained by the sliding filament model, in which myosin heads pull actin filaments within sarcomeres using ATP. The topic covers calcium, troponin, tropomyosin, the neuromuscular junction and relaxation, with attention to how filament length stays almost constant while the sarcomere shortens.
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