Vagus reflex

The vagus nerve plays a role in (amongst other things) controlling the pulse. The vagus reflex is a reaction which can reduce the pulse rate. Intentionally inducing a vagus reflex is sometimes used to treat tachycardia (racing pulse). The following stimuli may produce the vagus reflex:

• tensing the lower abdomen (similar to straining at stool)
• gentle pressure on the closed eyes
• a gulp of ice-cold water
• splashing ice-cold water on the face
• immersing the arms in ice-cold water
• finger stuck down the throat
• the insertion of an IV needle
• cough or sneeze (involuntary or autonomic works best)
• holding breath (after exhaling) - see Valsalva manoeuvre
• insertion of an object into the uterus such as an IUD