KIN 190 Lecture Notes - Lecture 4: Nebulin, Troponin, Endoplasmic Reticulum
Document Summary
Within myofibrils are smaller protein structures called filaments (myofilaments) Thin filaments = 8nm diameter, 1-2 nm long, composed mostly of protein actin. Thick filaments = 16nm diameter, 1-2 nm long, composed mostly of protein myosin. 2 thin filaments for 1 thick filament in overlap. Filaments in myofibril do not extend the length of a muscle fiber (arranged in compartments called sarcomeres) Sarcomere = basic functional unit of a myofibril. Z-discs = dense protein protein material separating one sarcomere from the next. *extent of overlap is dependant on whether the muscle is contracted, relaxed, or stretched. **the pattern of their overlap creates the striations in the single myofibrils and in the whole muscle fibers. A band - dark, middle part of sarcomere that extends the entire length of thick filaments and includes those parts of thin filaments that overlap thick filaments. I band - lighter, less dense area of sarcomere that contains remainder of thin filaments but no thick filaments.
