Alpha-2 receptors primarily regulate what in terms of vascular dynamics?

Alpha-2 receptors primarily regulate what in terms of vascular dynamics?

• A. Heart Rate
• B. Bronchodilation
• C. Blood Vessel Tone
• D. Digestive Motility

Answer: (C)

Alpha-2 adrenergic receptors regulate vascular dynamics mainly by controlling vascular tone. They sit on sympathetic nerve endings as autoreceptors, and when activated they dampen norepinephrine release. Less norepinephrine means less stimulation of vascular smooth muscle, reducing vasoconstriction and thus lowering vascular tone. In some vessels, postsynaptic alpha-2 receptors can cause constriction, but the overall effect on blood vessel tone comes from this modulation of norepinephrine release. Heart rate is driven largely by beta-1 receptor activity and autonomic balance; bronchodilation comes from beta-2 receptor activation; digestive motility is governed mainly by parasympathetic activity.

Alpha-2 adrenergic receptors regulate vascular dynamics mainly by controlling vascular tone. They sit on sympathetic nerve endings as autoreceptors, and when activated they dampen norepinephrine release. Less norepinephrine means less stimulation of vascular smooth muscle, reducing vasoconstriction and thus lowering vascular tone. In some vessels, postsynaptic alpha-2 receptors can cause constriction, but the overall effect on blood vessel tone comes from this modulation of norepinephrine release.

Heart rate is driven largely by beta-1 receptor activity and autonomic balance; bronchodilation comes from beta-2 receptor activation; digestive motility is governed mainly by parasympathetic activity.