Final answer:
A muscle fiber is at the cellular level of organization in the human body. It forms the basic building blocks of muscle tissue, which in turn contributes to the formation of organs and organ systems.
Step-by-step explanation:
A muscle fiber is considered to be at the cellular level of organization in the body. In terms of organization, the correct order from the smallest to the largest unit in muscle tissue is: filament, myofibril, muscle fiber, and fascicle. Muscle fibers are composed of many fibrils, which are packaged into orderly units within the fiber. These fibers then group together to form tissues. When multiple tissues combine, they form an organ, and organs work together to form organ systems.
Depolarization of the sarcolemma refers to a change in the muscle fiber's membrane potential, leading to the initiation of a muscle contraction. Tendons are connective tissues that attach muscle to bone. Conditions involving tendons like tendinitis are examples of muscular system disorders. For voluntary movements of limbs, skeletal muscles are used, while smooth and cardiac muscles function independently of conscious brain control.