Final answer:
Sweat glands secrete nitric oxide to stimulate vasodilation of skin arterioles, helping to reduce body temperature by allowing excess heat to dissipate through the skin.
Step-by-step explanation:
Sweat glands can also secrete a substance that stimulates vasodilation of skin arterioles to help reduce body temperature. The correct answer is nitric oxide (A).
Nitric oxide is a well-known vasodilator that plays an important role in the regulation of blood flow and blood pressure. When the body needs to release excess heat, such as during exercise or high environmental temperatures, sweat glands along with other systems work to cool the body. This includes the dilation of arterioles in the dermis so that the warm blood can reach the skin's surface and dissipate the heat into the environment, which can cause skin redness.