Which nerve is the parasympathetic nerve of the heart that slows heart rate?

Which nerve is the parasympathetic nerve of the heart that slows heart rate?

• A. Vagus nerve
• B. Sciatic nerve
• C. Phrenic nerve
• D. Glossopharyngeal nerve

Answer: (A)

The vagus nerve is the parasympathetic supply to the heart. It carries preganglionic fibers that reach the heart and release acetylcholine onto the SA and AV nodes via M2 muscarinic receptors. This action increases potassium conductance and decreases calcium currents, hyperpolarizing pacemaker cells and slowing their rate of depolarization. The result is a slower heart rate and reduced conduction velocity. Other nerves listed don’t provide the heart’s parasympathetic input.

The vagus nerve is the parasympathetic supply to the heart. It carries preganglionic fibers that reach the heart and release acetylcholine onto the SA and AV nodes via M2 muscarinic receptors. This action increases potassium conductance and decreases calcium currents, hyperpolarizing pacemaker cells and slowing their rate of depolarization. The result is a slower heart rate and reduced conduction velocity. Other nerves listed don’t provide the heart’s parasympathetic input.