what are the names of the "subunits" within the myofibrils that run the length of skeletal muscle fibers?

Sarcomeres

Explanation:

A muscle fiber is composed of many myofibrils, A sarcomere is the basic unit of a myofibril.

Sarcomeres are arranged in a stacked pattern throughout the muscle tissue, giving it a striped pattern. Sarcomeres are composed of thick and thin filaments. The thin and thick filaments interact  initiate the movement of muscle.

if two electrons have the same n, the same ℓ, and the same ml, then they are in the same orbital. the pauli exclusion principle states that no two identical fermions (a fancy word for electrons and other subatomic particles like electrons) may occupy the same quantum state in an atom simultaneously.