Final answer:
A hiccup is a non-respiratory movement caused by irritation of the diaphragm. It involves a sudden contraction of the diaphragm leading to an abrupt intake of air and the creation of the hiccup sound. Diaphragmatic irritation can also result in referred pain in the shoulder or neck due to the phrenic nerve's connections to cervical levels C3 to C5.
Step-by-step explanation:
The non-respiratory movement that is caused by irritation of the diaphragm is known as a hiccup. When the diaphragm becomes irritated, it can lead to a sudden contraction of the muscle, resulting in a quick intake of air that is suddenly stopped by the closure of the vocal cords, creating the characteristic hiccup sound.
Damage to internal organs can cause pain to be referred to different areas of the body due to shared nerve pathways. For example, irritation to the diaphragm, such as from an infection or injury, can feel like pain in the shoulder or neck because the phrenic nerve, which innervates the diaphragm, has connections to cervical spinal levels C3 to C5, the same levels from which somatosensory nerves in the neck and shoulders originate. This is why diaphragmatic irritation can result in pain that is felt in areas other than directly at the site of irritation.
The diaphragm also plays a critical role in various physiological processes other than respiration, such as defecation, urination, and childbirth, through its cooperation with the abdominal muscles in what is known as the Valsalva maneuver.