Calcium contributes to which of the following beyond bone health?

• A. Nerve impulses
• B. Oxygen transport
• C. Vitamin synthesis
• D. Blood pressure regulation

Answer: (D)

Calcium helps regulate blood pressure through its key role in vascular smooth muscle function and signaling. In the walls of blood vessels, calcium enters smooth muscle cells when channels open in response to stimuli. The calcium binds to calmodulin, activating myosin light-chain kinase, which enables the muscle to contract. More contraction increases vascular resistance and raises blood pressure. Conversely, when calcium entry is reduced or blocked—such as by calcium channel–blocking medications—smooth muscle relaxes, vascular resistance falls, and blood pressure decreases. While calcium is also essential for processes like nerve impulse transmission, the systemic effect most directly linked to everyday regulation of blood pressure is this control of vascular tone. The other options don’t describe a primary systemic regulatory role for calcium in the same way.