MEDICAL PHYSIOLOGY

Detailed explanation-1: -A sarcomere is the basic contractile unit of a myocyte (muscle fibre). A sarcomere is composed of two main protein filaments (thin actin and thick myosin filaments) which are the active structures responsible for muscular contraction.

Detailed explanation-2: -The sarcomere is the fundamental contractile unit of the myofibril. Z lines separate each sarcomere. The A bands, located at the center of each sarcomere, contain the thick filaments, which may overlap with thin filaments.

Detailed explanation-3: -There are between 2, 000 and 2, 500 sarcomeres found together in linked coils in each 10 millimetres of muscle fibre. To watch the sarcomeres in action, the researchers first had to isolate a single myofibril (the basic rod-like units which make up muscle tissue) and then zoom in on an individual sarcomere.

Detailed explanation-4: -The contraction of a striated muscle fiber occurs as the sarcomeres, linearly arranged within myofibrils, shorten as myosin heads pull on the actin filaments. The region where thick and thin filaments overlap has a dense appearance, as there is little space between the filaments.

Detailed explanation-5: -For a muscle cell to contract, the sarcomere must shorten. However, thick and thin filaments-the components of sarcomeres-do not shorten. Instead, they slide by one another, causing the sarcomere to shorten while the filaments remain the same length.