Which type of myofilament is primarily made up of myosin proteins?

The type of myofilament primarily composed of myosin proteins is known as thick filaments. Myosin is a motor protein that plays a crucial role in muscle contraction by interacting with actin filaments during the process of muscle shortening. Thick filaments are essential for generating the force necessary for muscle contractions. They have a structure characterized by long, fibrous tails and globular heads, which can bind to actin on the thin filaments.

Thick filaments are especially dominant in the sarcomere, the fundamental unit of muscle contraction in striated muscle. This arrangement allows for the sliding filament theory of muscle contraction to occur, where myosin heads pull actin filaments toward the center of the sarcomere, resulting in muscle contraction. Understanding the composition and function of thick filaments is key to grasping how muscle physiology operates in human anatomy.