MUSCLE PHYSIOLOGY

Detailed explanation-1: -Sarcomere, repeating unit form myofibril. Myofibrils are essentially polymers, or repeating units, of sarcomeres. The shortening of the individual sarcomeres leads to the contraction of the individual muscle fibres, leading to muscle contractions..

Detailed explanation-2: -Sarcomeres are the smallest functional contractile unit of muscle, and myofibrils are striated muscle organelles that are comprised of sarcomeres that are strictly aligned in series.

Detailed explanation-3: -Sarcomeres are connected end to end by Z lines along the length of each myofibril. Thin filaments attach to the Z lines and make up the I zone of the sarcomere. Thick filaments overlap the thin filaments in the middle of the sarcomere, making up the A zone.

Detailed explanation-4: -Each sarcomere consists of a central A-band (thick filaments) and two halves of the I-band (thin filaments). 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.

Detailed explanation-5: -Myofibrils are composed of long proteins including actin, myosin, and titin, and other proteins that hold them together. These proteins are organized into thick, thin, and elastic myofilaments, which repeat along the length of the myofibril in sections or units of contraction called sarcomeres.