This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General physiology, Subject name: Physiology
Skeletal muscle contraction ends when 
Select and explain. 
A. Ions move out of cytoplasm, B. Ach is absorbed frm the nmj, C. Closure and indrawing of receptors, D. Decreased calcium outside reticulum
D: Decreased calcium outside reticulum
Answer: D: Decreased calcium outside reticulum 
Explanation: Muscle contraction ends usually when signals from motor neuron stops which repolarises sarcolemma and closes voltage gated calcium channals in sarcoplasmic reticulum. Ref:Guyton and Hall textbook of medical physiology 12th edition,page number:82,83