About the Brain, Hiccups and Laughter

The breathing movements that expand and contract the chest are controlled by the medulla oblongata, a part of the brain located at the back of the skull, where the spinal cord originates. The spinal cord is made up of cells and nerve fibers that transmit commands to the diaphragm and intercostal muscles to cause the muscle fibers to contract or relax.

In the medulla oblongata there are two respiratory control centers that work in a coordinated manner: one determines whether there is excess carbon dioxide in the blood and issues commands to exhale; the second determines the amount of oxygen and regulates the frequency of breaths.

The so-called “hiccup center” is also located in the brain. Hiccups are a sudden contraction of the diaphragm and vocal cords caused by inhaling too much air or eating and drinking too much. The characteristic sound occurs when the epiglottis closes or when the vocal cords open when exhaled air hits them.

Laughter is also caused by a series of sudden shocks of the diaphragm, which cause air to rise up the trachea and pass through the resonator. Thus, both hiccups and laughter are controlled by the brain through the respiratory centers.