The myofilaments used during muscle contractions will return to their resting state when the relax.

The correct answer is sarcomere.

A sarcomere refers to the fundamental unit of striated muscle tissue. It is the reiterating unit between the two Z lines. The skeletal muscles comprise tubular muscle cells known as muscle fibers or myocytes that are produced in the procedure called myogenesis.

When the muscle fibers of a motor unit attain an impulse, it instigates a response in each sarcomere between the myosin and actin filaments. This response leads to a start of a contraction and the sliding filament theory.

answer: accepted answer: aquatic animals use the oxygen dissolved in water to carry out respiration. since the amount of dissolved oxygen in water is low as compared to the amount of oxygen in the air, therefore the rate of breathing in aquatic animals is much faster than it is in terrestrial animals.

explanation: