Muscle Anatomy: The scale and arrangement of muscles goes from muscle organ, fascicle, fiber, myofibril, to myofilaments within repeating sarcomere units (Fig. 1) 1. A muscle organ = whole muscle group, made of a bunch of fascicles (ex. biceps brachii).2. muscle fascicle = bundle of muscle muscle fibers. 3. muscle fiber = a single muscle cell, which is innervated by a motor neuron in the neuromuscular junction (the junction between a motor neuron and muscle fiber).. muscle fascicle = bundle of muscle muscle fibers. 3. muscle fiber = a single muscle cell, which is innervated by a motor neuron in the neuromuscular junction (the junction between a motor neuron and muscle fiber).