Hiccups often appear without warning and sometimes disappear just as mysteriously.
A hiccup involves an involuntary contraction of the diaphragm followed by rapid closure of the vocal cords.
Many ordinary situations can e39 com irritate or stimulate the pathways involved in the hiccup reflex.
For E39 readers, this familiar annoyance is a simple example of the nervous system acting without conscious control.
Hiccups may be annoying, but they offer a quick demonstration of how breathing muscles and nerves interact.