Final answer:
The major cause of decreased blood pressure with increased anesthetic is vasodilation and reduced myocardial activity. Anesthetics relax blood vessel smooth muscles, leading to wider vessels and lower pressure. They also suppress heart function, further dropping blood pressure.
Step-by-step explanation:
The major cause of decreased blood pressure when increasing volatile anesthetic is the resultant vasodilation and the depression of myocardial activity. Volatile anesthetics have a relaxant effect on the smooth muscles, including those in the blood vessels, leading to vasodilation (widening of blood vessels), which in turn lowers blood pressure. Additionally, these anesthetics can depress the function of the heart, reducing the force of contraction and cardiac output, which further contributes to a decrease in blood pressure.
For comparison, cocaine use causes vasoconstriction, or the narrowing of blood vessels, which would likely lead to an increase in blood pressure. Conversely, as illustrated by the anesthetic example, vasodilation due to the administration of an anesthetic agent would have the opposite effect, decreasing blood pressure.