Out of the following given choices;
1) There is a charge difference across the sarcolemma.
2) Sodium-potassium pumps are active.
3) Calcium is stored in the sarcoplasm.
4) ACh receptors are open.
The answer is 1, 3 and 4. When a muscle is at rest, the Ca2+ ions are still sequestered in the sarcoplasm until an impulse induces depolarization. ACh receptors are also not bound by acetylcholine which is the primary receptor-neurotransmitter in muscle for motor nerve-muscle communication that controls muscle contraction.