Library · Physiology
Why you get hiccups
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A hiccup, called singultus in medicine, is a sudden contraction of the diaphragm, the large muscle that sits below the lungs, along with the muscles between the ribs, the intercostals, and it asks no permission. Right after that the glottis, the opening in the throat that air passes through, snaps shut, and that closing is what makes the noise.
What sets it off is a reflex arc, a round-trip circuit that runs without you deciding anything. The signal travels up the vagus nerve, the phrenic nerve and some fibers of the sympathetic system, and comes back through the phrenic nerves to the diaphragm. It is a doorbell that someone presses by accident and that then rings on its own.
The closing of the glottis is not incidental. It is what completes the reflex, and without it the episode would end in hyperventilation, meaning breathing too much.
Almost everyone gets hiccups at some point, and most of the time they go away on their own within two days.
In brief
A hiccup, or singultus, is a sudden involuntary contraction of the diaphragm and intercostal muscles, followed by an abrupt closing of the glottis that makes the sound.
A reflex arc drives it: the signal travels up vagal, phrenic and sympathetic fibers, and returns through the phrenic nerves to the diaphragm.
A doorbell someone presses by accident that rings on its own.
That closure completes the reflex; without it, the episode would end in hyperventilation.
Almost everyone gets hiccups, and most episodes resolve in under 48 hours.
Sources (1)
- National Center for Biotechnology Information, StatPearls PublishingSingultus, StatPearlsPublished
This page explains the topic in general terms; it does not tell anyone what treatment to follow.
Updated