Which nerve mediates the vagal slowing of the heart during the Valsalva maneuver?

• A. Vagus nerve
• B. Accessory nerve
• C. Trigeminal nerve
• D. Hypoglossal nerve

Answer: (A)

The main concept is parasympathetic control of heart rate. The vagus nerve provides the heart’s parasympathetic innervation, releasing acetylcholine onto the SA and AV nodes to slow firing and slow conduction. During the Valsalva maneuver, increased intrathoracic pressure activates reflexes that boost vagal tone, leading to a transient slowing of the heart (bradycardia).

The other nerves don’t regulate the heart in this way. The accessory nerve mainly controls neck muscles, the trigeminal nerve handles facial sensation and mastication, and the hypoglossal nerve moves the tongue. None of these directly mediate vagal slowing of the heart.