Which autonomic division increases heart rate?

• A. Sympathetic
• B. Somatic
• C. Enteric
• D. Parasympathetic

Answer: (A)

Sympathetic stimulation increases heart rate by activating the heart’s pacemaker and conduction system. When this division is engaged, nerves release norepinephrine onto β1-adrenergic receptors in the SA node, AV node, and myocardium, which raises the rate of pacemaker firing and speeds electrical conduction. This results in a faster heart rate and stronger contractions to boost blood flow during activity or stress. In contrast, parasympathetic activity, via acetylcholine on muscarinic receptors, slows the heart. The somatic nervous system controls voluntary muscles, and the enteric system manages the gut, so they don’t set heart rate. Therefore, the autonomic division that increases heart rate is the sympathetic.