Which of the following pumps are found in large numbers on the cisternae of the sarcoplasmic reticulum?

Cisternae are the bulged region of sarcoplasmic reticulum which are a store house of calcium. Hence the pumps present on these are Ca2+ - ATPase pumps. A nerve stimulus causes spread of action potential through T-tubules of a muscle fibre. This triggers release of calcium ions from the cisternae which bind to troponin of thin filaments. The muscle contraction is initiated.