Final answer:
Increasing the sympathetic nervous system activity raises the mean arterial pressure by enhancing cardiac output and vasoconstriction, while increasing vagal (parasympathetic) activity reduces it through heart rate slowing and vasodilation.
Step-by-step explanation:
An increase in SNS rate while holding the vagal rate constant increases mean arterial pressure (MAP), and an increase in vagal rate while holding the SNS rate constant decreases MAP.
When the sympathetic nervous system (SNS) is activated, it causes vasoconstriction of the arterioles, which increases vascular resistance. This leads to an increase in MAP.
On the other hand, an increase in vagal rate (parasympathetic stimulation) causes vasodilation, which decreases vascular resistance and ultimately decreases MAP.
The cardiovascular system is tightly regulated by the sympathetic nervous system (SNS) and the parasympathetic system, specifically through the vagal nerve. When the SNS rate is increased while the vagal rate is held constant, this results in an increase in mean arterial pressure (MAP).
On the other hand, when the vagal rate is increased while holding the SNS rate constant, MAP decreases. This differential impact on MAP is because SNS activation leads to heightened cardiac output and vasoconstriction, which in turn elevates blood pressure, while increased parasympathetic (vagal) activity slows the heart rate and induces vasodilation, thereby lowering MAP.