Question

in skeletal muscles, which of the following is true regarding the calcium needed for contraction? multiple choice it is stored in the sarcoplasmic reticulum. it is transported into the cell from the extracellular fluid. it is stored in the sarcoplasm. it is stored bound to troponin when the cell is relaxed. skeletal muscles use sodium, not calcium, for contraction

Explanation:

In skeletal muscles, calcium needed for contraction is stored in the sarcoplasmic reticulum. When a muscle is stimulated to contract, calcium is released from the sarcoplasmic reticulum into the sarcoplasm. It binds to troponin, causing a conformational change that exposes binding - sites for myosin on actin filaments, leading to muscle contraction. Calcium is not primarily transported from extracellular fluid in skeletal muscle contraction, nor is it stored in the sarcoplasm or bound to troponin when relaxed. And skeletal muscles use calcium, not sodium, for contraction.

Answer:

It is stored in the sarcoplasmic reticulum.