What effect does the sympathetic nervous system have on blood vessels?

The sympathetic nervous system plays a critical role in the body's 'fight or flight' response, influencing various physiological processes to prepare the body for immediate action. One of these effects is vasoconstriction, which is the contraction of the smooth muscle in the walls of blood vessels, particularly the arterioles. When stimulated by the sympathetic nervous system, neurotransmitters such as norepinephrine are released, leading to the contraction of vessel walls. This response helps to redirect blood flow away from non-essential areas, such as the gastrointestinal tract, and towards vital organs and muscles, enhancing overall readiness for physical activity or stress.

In particular situations, this action serves to increase blood pressure and ensure that the most critical areas of the body receive adequate blood supply during times of stress, supporting functions like strength and endurance. Consequently, the assertion that the sympathetic nervous system allows blood vessels to contract is supported by its established role in regulating vascular tone and blood flow dynamics during stress responses.