Which nerves decrease heart rate?

Which nerves decrease heart rate?

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

Answer: (C)

Parasympathetic nerves slow the heart by sending acetylcholine to the heart’s pacemaker tissues (the SA and AV nodes). This causes an increase in potassium conductance and a slower rate of spontaneous depolarization, which lengthens the time between beats and lowers heart rate. At rest, parasympathetic influence dominates, keeping the heart rate relatively low. When needed, sympathetic nerves increase heart rate, so the balance shifts upward during activity. The other options don’t fit because enteric nerves govern digestion, somatic nerves control voluntary muscles, and sympathetic nerves raise, not lower, heart rate.

Parasympathetic nerves slow the heart by sending acetylcholine to the heart’s pacemaker tissues (the SA and AV nodes). This causes an increase in potassium conductance and a slower rate of spontaneous depolarization, which lengthens the time between beats and lowers heart rate. At rest, parasympathetic influence dominates, keeping the heart rate relatively low. When needed, sympathetic nerves increase heart rate, so the balance shifts upward during activity. The other options don’t fit because enteric nerves govern digestion, somatic nerves control voluntary muscles, and sympathetic nerves raise, not lower, heart rate.