Which Autonomic Receptor Mediates an Increase in Heart Rate?
A) $\alpha$

Which autonomic receptor mediates an increase in heart rate?

A) Adrenergic $\alpha$ receptors
B) Adrenergic $\beta_{1}$ receptors
C) Adrenergic $\beta_{2}$ receptors
D) Cholinergic muscarinic receptors
E) Cholinergic nicotinic receptors