The skeletal muscle, responsible for voluntary contraction is composed of 1) Myofilaments 2) Myofibrilles 3) Muscle fibers 4) Muscle (from the left to the right in the image)
What is the composition of the skeletal muscle?
The elements composing the skeletal muscle are,
- Myofilaments ⇒ Actine and miosine
- Sarcomere ⇒ It is the functional unit with the contractile apparatus. Composed of the Z band, A and I bands, and H zone.
- Myofibrilles ⇒ They have the Functional units
- Muscle fibers ⇒ Surrounded by endomysium
- Fascicle ⇒ Group of fibers surrounded by perimysium.
- Muscle ⇒ Group of fascicles surrounded by epimysium.
The sarcomere is the contractile unit in a skeletal muscle. The thick myosin myofilaments are located in the central region of the sarcomere, which corresponds to the A band.
Thin filaments united to the Z lines, extends to the interior of the A band until they reach the border of the H band.
The I band is formed solely of thin actin filaments, belonging to two sarcomeres adjacent to a Z line.
When the muscle contracts, the muscular fiber gets shorter and thicker due to the reduction in length of the sarcomere.
- The H line and the I band get shorter.
- The Z lines get closer to the A band, meaning that they get closer to each other. The A band keeps constant in length.
- This change is produced by movement mechanisms that involve a change in the relative position of actin and myosin filaments.
For a better understanding about muscle contraction, look at the attached files.
From the left to the right,
1) Myofilaments
2) Myofibrilles
3) Muscle fibers
4) Muscle
You can learn more about skeletal muscle structure at
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