Which cardiovascular effect is characteristic of cholinergic stimulation, particularly after injection?

Which cardiovascular effect is characteristic of cholinergic stimulation, particularly after injection?

• A. Bradycardia and vasodilation
• B. Hypertension
• C. Tachycardia
• D. No change in heart rate

Answer: (A)

Cholinergic stimulation activates the parasympathetic system, mainly through muscarinic receptors in the heart and blood vessels. In the heart, activating M2 receptors slows the SA node and slows AV nodal conduction, producing a lower heart rate (bradycardia). In the vasculature, acetylcholine can induce endothelium-dependent vasodilation via M3 receptors, leading to nitric oxide release and relaxation of vascular smooth muscle, which lowers peripheral resistance. Taken together, these effects after injection produce both a slower heart rate and vasodilation. Hypertension would not fit because sympathetic activity raises blood pressure, while direct cholinergic stimulation tends to lower it; tachycardia or no change would not reflect the predominant bradycardic and vasodilatory responses seen with cholinergic activity.

Cholinergic stimulation activates the parasympathetic system, mainly through muscarinic receptors in the heart and blood vessels. In the heart, activating M2 receptors slows the SA node and slows AV nodal conduction, producing a lower heart rate (bradycardia). In the vasculature, acetylcholine can induce endothelium-dependent vasodilation via M3 receptors, leading to nitric oxide release and relaxation of vascular smooth muscle, which lowers peripheral resistance. Taken together, these effects after injection produce both a slower heart rate and vasodilation. Hypertension would not fit because sympathetic activity raises blood pressure, while direct cholinergic stimulation tends to lower it; tachycardia or no change would not reflect the predominant bradycardic and vasodilatory responses seen with cholinergic activity.