The following events are associated with muscle contraction. Which of the following best describes the order in which these events occur, following the initiation of a contraction by a nerve impulse? 1. Tubules transmit electrical impulses throughout muscle cell. 2. Myosin contacts actin and pulls it towards the center of the sarcomere. 3. Acetylcholine binds to receptors on the muscle. 4. Troponin-tropomyosin complex shifts to expose myosin binding sites. 5. Calcium is released from the sarcoplasmic reticulum.