Final answer:
Muscle tissue exhibits contractility, allowing it to forcibly contract and shorten, and elasticity, enabling it to return to its original length upon relaxation. The processes of contraction and relaxation are dependent on proteins within the muscle fibers as well as the presence of ATP and calcium ions.
Step-by-step explanation:
When discussing muscle function, we often speak about their unique properties such as contractility, which is the muscle's ability to shorten forcibly, and elasticity, which allows a muscle to return to its original length when relaxed. The contractility of a muscle is evident during the contraction phase or twitch contraction phase, where tension increases as a result of the interaction between myofibrils within the muscle fibers, primarily between actin and myosin proteins. Muscles lengthen as the tension is diminished, showcasing their elasticity, an ability to stretch and rebound. The process involves the restoration of the length-tension relationship within the sarcomeres that make up muscle fibers.
The endomysium plays a role here as well; it is a type of loose, well-hydrated connective tissue that covers each muscle fiber and facilitates the changes in muscle length. Moreover, the action of muscle contraction and relaxation is dependent on the biochemical energy provided by adenosine triphosphate (ATP) and the presence and subsequent removal of calcium ions (Ca++) for these processes to occur efficiently.
Thus, a muscle can contract and it becomes short when it does so; when it relaxes, it returns to its original length due to elasticity.