Option 1 states that muscle contraction and relaxation involve the movement of Zn+ ions. However, this is incorrect. The movement of Zn+ ions does not play a significant role in muscle contraction and relaxation.

Option 2 states that muscle contraction and relaxation involve the Ca 1+ ions of blood. This is also incorrect. While Ca+ ions are involved in muscle contraction and relaxation, they are not derived directly from the blood.

Option 3 is the correct answer. Muscle contraction and relaxation involve the release of Ca++ ions from the sarcoplasmic reticulum (SR) and the pumping of Ca+ ions back into the SR. The sarcoplasmic reticulum is a specialized network of membrane-bound tubules within muscle fibers that stores and releases calcium ions.

Option 4 states that muscle contraction and relaxation involve the exchange of Na+ and K+ ions. This is incorrect. Although Na+ and K+ ions are involved in muscle function, they primarily have roles in generating action potentials, not in muscle contraction and relaxation.

Therefore, the correct statement regarding muscle contraction and relaxation is option 3.