Understanding the Sarcomere- Structure, Components, and Changes During Muscle Contraction
Indeed, the sliding filament theory best describes striated muscle contractions. The theory is crucial in explaining the molecular mechanisms involved in muscle contraction at the sarcomere level. Two proteins are involved in muscle contraction, myosin, and actin (Brunello & Fusi, 2024). The two proteins must be arranged repetitively within the sarcomere for a contraction to occur.
Essentially, a sarcomere can be defined as the basic unit of muscle fiber. As stated in the above paragraph, the critical components of a sarcomere include the myosin and actin filaments. These components must interact in a coordinated manner for effective muscle contraction (Seow, 2020). The myosin is a protein with thick filaments. The molecules generally have a rounded head, which aids in interaction with actin filaments, generating force for muscle contraction.
On the other hand, the actin filaments are helical and thin. The protein is anchored to the Z-d- discs at the periphery of the sarcomere. The actin filaments slide over the myosin filaments, shortening the sarcomere to facilitate muscle contraction (Brunello & Fusi, 2024). The troponin proteins on the actin filaments play a significant role in muscle contraction through binding with calcium ions, which initiates the interaction of myosin and actin filaments. The tropomyosin protein wraps the actin filaments around, which blocks myosin from binding with actin when there are no calcium ions. When the calcium ions bind to the troponin proteins, the tropomyosin proteins undergo a conformational change, exposing the myosin binding sites on the actin allowing muscle contraction (Seow, 2020). The other protein found in the actin is nebulin, which regulates the length of actin filaments during contraction to ensure their stability within the sarcomeres.
References
Brunello, E., & Fusi, L. (2024). Regulating Striated Muscle Contraction: Through Thick and Thin. Annual Review of Physiology, 86, 255-275. https://www.annualreviews.org/content/journals/10.1146/annurev-physiol-042222-022728
Seow, C. Y. (2020). An introduction to smooth muscle mechanics. Cambridge Scholars Publishing.
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Question 
Skeletal and cardiac muscle tissues contract via a process known as the sliding filament theory. To create these contractions, the muscle must be arranged in a specific pattern known as a sarcomere.
Understanding the Sarcomere- Structure, Components, and Changes During Muscle Contraction
Discuss the different components of the sarcomere, how they are arranged, and what changes (if any) happen to them when the muscle is contracted.