MEDICAL PHYSIOLOGY

Detailed explanation-1: -The I bands contain only thin (actin) filaments, whereas the A bands contain thick (myosin) filaments. The myosin and actin filaments overlap in peripheral regions of the A band, whereas a middle region (called the H zone) contains only myosin.

Detailed explanation-2: -The I-band from two adjacent sarcomeres meets at the Z-line. The central portion of the A-band is the M-line, which does not contain actin. The figure shows the positioning of the major filament systems that compose the sarcomere: titin, actin (thin), and myosin (thick) filaments.

Detailed explanation-3: -Sarcomeres have a region devoid of myosin filaments called I-band and a region devoid of actin filaments called H-zone. In the middle of these regions are big protein complexes that hold the actin or the myosin filaments in place, the Z-disc and the M-line, respectively (Lemke and Schnorrer, 2017).

Detailed explanation-4: -H-band: The area adjacent to the M-line, where myosin myofilaments are not superimposed by actin myofilaments.