myofibrilákból

Myofibrils are the fundamental contractile units of muscle cells, also known as muscle fibers. These long, cylindrical organelles are packed with proteins that enable muscle contraction and movement. Each myofibril is composed of repeating units called sarcomeres, which are the smallest functional components of muscle.

Within a sarcomere, two primary types of protein filaments are arranged in a highly organized manner: thick filaments and thin filaments. Thick filaments are primarily composed of the protein myosin, while thin filaments are mainly composed of the protein actin. These filaments are anchored at specific points within the sarcomere, creating a characteristic striated appearance when viewed under a microscope, which gives skeletal muscle its striped look.

The sliding filament theory explains how muscle contraction occurs. During contraction, the myosin heads bind to actin filaments and pull them towards the center of the sarcomere. This process shortens the sarcomere and, consequently, the entire myofibril. This shortening generates the force required for muscle movement. Energy for this process is supplied by adenosine triphosphate (ATP). The coordinated contraction of millions of myofibrils within a muscle fiber results in the overall contraction of the muscle. Myofibrils are essential for all forms of muscle activity, from voluntary movements to involuntary processes like heartbeat.