What is the H zone?
myosin only
The H zone (or H band) is a region within a sarcomere, which is the basic functional unit of a muscle fiber. The H zone refers to the lighter area in the center of the sarcomere, which contains only myosin filaments (a type of thick filament), while the darker regions on either side of it contain both myosin and actin filaments (a type of thin filament).
During muscle contraction, the myosin filaments pull the actin filaments towards the center of the sarcomere, causing the H zone to become thinner and eventually disappear altogether. This process is what shortens the sarcomere as a whole, leading to muscle contraction.
The size and appearance of the H zone can be affected by various factors, such as exercise or disease. For example, regular exercise can lead to an increase in muscle mass and a thicker H zone, while certain conditions may cause the H zone to become narrower or even disappear altogether. Overall, the H zone is an important aspect of muscle function and plays a crucial role in the process of muscle contraction.
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