2. (All-or-nothing for 0.5 pts) Arrange the steps of excitation that occur at the neuromuscular junction. 1. ACh receptors open and allow Na" to enter the muscle fiber, generating an action potential on the sarcolemma 2. Synaptic vesicles containing the neurotransmitter, ACh undergo exocytosis. 3. ACh is quickly broken down to Acetate and Choline by Acetylcholine Esterase. 4. ACh is released into the synaptic cleft and binds to ACh receptors on the motor end plate. 5. Action potential arrives at the synaptic end bulb of motor neuron and causes opening of voltage gated Ca² channels. 3. (0.5 pts) A contraction in which the muscle is developing force but not shortening and no visible movement is seen is called 4. (0.5 pts) Increasing the amount of force generated by increasing the number of motor units is called 5. (0.5 pts) The inability to contract caused by long periods of muscle contraction is called 6. (0.5 pts) The EMG primarily records the electrical signals of groups of (muscle/nerve) cells.