Which of the following increases heart rate?

Atropine is a medication that acts as an anticholinergic agent, specifically blocking the effects of the neurotransmitter acetylcholine on the heart. By inhibiting the parasympathetic nervous system, atropine leads to an increase in heart rate. This effect is particularly useful in situations where a patient is experiencing bradycardia, a condition characterized by abnormally slow heart rates. Administering atropine counteracts the vagal tone that slows the heart, thereby leading to an increase in heart rate.

Other options, while related to physiological responses, do not primarily serve to increase heart rate in the same direct manner that atropine does. Glucagon has effects on glucose metabolism and can influence heart function, but its primary role is not to raise heart rate directly. Insulin has various functions in the body, primarily related to glucose uptake, and does not directly impact heart rate positively; in some cases, it can lower heart rate. Epinephrine, while it does increase heart rate by activating beta-adrenergic receptors, is often used in critical situations such as cardiac arrest, where its broader effects on the body can be more complex than simply raising heart rate. Atropine’s specific mechanism of blocking vagal influences directly