Sarcomere

The sarcomere is the basic contractile unit of striated muscle tissue. This structure is key to understanding how muscles contract and perform their functions in the body.

The sarcomere is located inside the myofibril, which is the main structure of muscle tissue. Myofibrils are made up of parallel protein filaments called actin and myosin, which form sarcomeres. Sarcomeres join together to form myofibrils, which in turn form muscle fibers.

The sarcomere consists of two telofragments called Z disks and the A disk, which is located in the middle of the sarcomere. The halves of the Z disks lying on either side of the A disk are called the I disks. The A disk contains thick myosin filaments, and the I disks contain thin actin filaments.

When muscles contract, myosin filaments slide along actin filaments, causing the sarcomere to shorten. This process occurs due to the energy contribution in the form of ATP (adenosine triphosphate) and calcium, which is released from special stores in the muscle cell.

Sarcomeres play an important role in muscle contractility and their function in the body as a whole. Understanding the structure and function of sarcomeres is important for understanding the mechanisms underlying many physiological processes associated with muscle activity.

In conclusion, the sarcomere is the basic contractile unit of striated muscle tissue, which plays an important role in muscle contractility and function in the body as a whole. Understanding the structure and function of sarcomeres is fundamental to understanding the mechanisms underlying muscle activity.

Sarcomeres are the basic contractile unit of striated muscles. They are sections of myofibrils located between telofragments. Each sarcomere consists of disk A, lying in the center, and two halves of disks I on each side. Disc A is a dense protein structure that contains actin and myosin, as well as other proteins. The halves of disc I contain the protein tropomyosin, which plays an important role in muscle contraction.

Sarcomeres are connected to each other by bridges consisting of strands of thin mitochondria. These bridges enable the transfer of energy from mitochondria to myosin, allowing the muscle to contract.

Muscle contraction occurs due to the interaction of actin and myosin. Actin is a globular protein that forms the backbone of myofilaments. Myosin is also a globular protein, but it is larger in size and contains several functional domains. During muscle contraction, myosin binds to actin through its functional domains, and as a result of this interaction, muscle contraction occurs.

A sarcomere is a structure about 2 microns (0.02 mm) long that is involved in muscle contraction. It consists of disk A, disk I and two telofragments held together by Z-lines. When a nerve impulse passes through the neuromuscular synapse, part of the Ca enters the telofragment, which leads to swelling of the bodies. They come closer together and are rounded (i.e., they form a rounded terminal apparatus). This is combined with relaxation of discs A and I. Part of Ca from one telofragment enters the second, causing a similar effect. Thus, the sarcomeres of all telophragms are connected and form a series of so-called stalk cell structures. When action potentials occur, the A disks begin to change conformation, leaving their limits and closing the chains of actin filaments to form a circuit between the telophragmata. As a result, the Ca ion flow to the phragm body stops and relaxation occurs. To contract a muscle, tension must be applied to each successive sarcomere. Over time, the sarcomere manages to activate, and the process is completed. The frequency of formation of new sarcomere formations is not enough to constitute the potential for a full contraction, since the next cut is far from the previous one - at the distance of the sarcomere. The number of sarcomas is approximately 600 thousand.

Sarcomeres provide a unique ability to control the force, speed and frequency of muscle contraction. Depending on the type of muscle, muscle tissue also has a different structure. To begin with, it is important to say that there are two types of muscles - smooth and striated. Striated muscle consists of cylindrical muscle fibers. It originates from the corresponding muscular cranial trunks and is therefore functionally called extramuscular. These muscles form skeletal muscles. Due to the fact that during contraction this muscle group develops significant strength, they actively participate in the implementation of work in cost and social terms.