Myofibrils are _. View Available Hint(s) Myofibrils are _. made of a series of sarcomeres proteins that cover active sites on actin bundles of muscle cells inside a whole muscle connections between actin and myosin
The Correct Answer and Explanation is :
The correct answer is: Myofibrils are made of a series of sarcomeres.
Explanation:
Myofibrils are the contractile threads found in muscle cells (also called muscle fibers). They are composed of repeated units known as sarcomeres, which are the basic functional units of muscle contraction. Each myofibril is a long, cylindrical structure that runs the length of a muscle fiber and is densely packed with sarcomeres arranged end to end.
Structure of a Sarcomere:
A sarcomere is the smallest structural and functional unit of a myofibril. It is bounded by Z-discs on both ends, which anchor the actin (thin filaments). In between the Z-discs, myosin (thick filaments) are interdigitated with the actin filaments. The interaction between these filaments, powered by ATP, enables muscle contraction. This sliding filament model describes how actin and myosin filaments slide past each other during contraction, shortening the sarcomere, and thus shortening the entire muscle.
Role in Muscle Contraction:
When a muscle contracts, the myosin heads attach to actin filaments to form cross-bridges and pull the actin filaments towards the center of the sarcomere. This process shortens the sarcomere, which collectively leads to the shortening of the myofibrils and the entire muscle fiber, generating the force necessary for movement. The contraction is initiated by signals from the nervous system, leading to the release of calcium ions that allow myosin heads to bind to actin.
Summary:
Thus, myofibrils are made up of repeating units of sarcomeres, which are responsible for muscle contraction. This highly organized arrangement of sarcomeres within myofibrils allows skeletal muscles to produce force and movement in a highly efficient and coordinated manner.