How does IP3 influence muscle contraction and nerve cell secretion?

• A. IP3 directly binds to muscle fibers and nerve cells to initiate contraction and secretion.
• B. IP3 releases calcium from the endoplasmic reticulum, which then triggers muscle contraction and nerve cell secretion.
• C. IP3 inhibits calcium release, preventing muscle contraction and nerve cell secretion.
• D. IP3 activates protein kinase C, which then causes muscle contraction and nerve cell secretion.

Answer: (B)