ttps:////»https://www.w3.org/TR/REC-html40/loose.dtd»>
Matheus William Ribas,
Passo Fundo, RS
There are two explanations for that tear flowing after a good laugh. The first is emotional: we cry because we are happy. By letting out a laugh like that, we trigger a reaction in the limbic system, a region of the brain that controls emotions.
The other explanation is physiological. Some people have an unusual distribution of nerves in their face. Because of this, when they open their mouths to laugh (or even to yawn), the set of nerves that connect the jaw to the salivary glands ends up stimulating the lacrimal gland.
The hypothalamus is one of the brain regions that make up the limbic system. Upon detecting the emotion of joy, it orders the production of acetylcholine, a neurotransmitter that travels through the parasympathetic nervous system, connected to the lacrimal gland.
This is because both the nerves and the tear glands are connected to the parasympathetic nervous system, the part of the nervous system that stimulates relaxing activities in glands and muscles.
The two phenomena can occur either alone or together. In both cases, the lacrimal gland receives impulses from the nervous system and goes into action, producing tears that accumulate in the lacrimal lake, until they overflow, making us cry.