Atropine increases heart rate by blocking vagal effects. What is this type of effect called?

• A. Negative chronotropic
• B. Positive chronotropic
• C. Inotropic
• D. Dromotropic

Answer: (B)

The main idea is how the autonomic nervous system controls heart rate through chronotropic effects. Chronotropy refers to changes in heart rate. A positive chronotropic effect means an increase in rate, while a negative chronotropic effect means a decrease. The vagus nerve provides parasympathetic input that slows the heart by acetylcholine acting on muscarinic receptors. Atropine blocks those receptors, removing the slowing influence. With that brake removed, the heart rate rises, which is a positive chronotropic effect. The other terms describe different aspects: inotropic relates to the strength of contraction, dromotropic to the speed of electrical conduction, and negative chronotropic would imply slowing the rate.