Final answer:
Low blood volume due to hemorrhage from an event like a motor vehicle accident is caused by the loss of blood when blood vessels are severed, leading to hypovolemia and potentially to hypovolemic shock if untreated.
Step-by-step explanation:
The cause of low blood volume due to hemorrhage, such as from a motor vehicle accident, is the loss of blood from the circulatory system when blood vessels are severed. This condition, known as hypovolemia, can lead to a type of circulatory shock termed hypovolemic shock. Hemorrhage is a serious medical condition where blood loss exceeds the body's hemostatic capacity, which is the body's ability to stop bleeding and repair damaged vessels. Other regulatory mechanisms help maintain blood pressure, so symptoms may not be apparent until 10-20 percent of blood volume is lost. Medical intervention typically involves restoring blood volume through intravenous fluid replacement, and in more severe cases, blood transfusions.