Question: I understand that when people are upset they can often cry but I was wondering what makes the eyes produce tears and why people may cry when they are happy or feel over emotional?

Amy MacQueen answered on 17 Jun 2011:

Hey cspooner!

Right I didn’t know the answer to this one (its a good question) but Wikianswers would suggest this…

“Crying or weeping is increased lacrimation due to strong emotional stress, depression or physical pain. This practice is not restricted to negative emotions; many people cry when extremely happy. In humans, emotional tears can be accompanied by reddening of the face and sobbing – cough-like, convulsive breathing, sometimes involving spasms of the whole upper body.

Tears brought about by emotions have a different chemical make up than those for lubrication; emotional tears contain more of the protein-based hormones prolactin, adrenocorticotropic hormone, and leucine enkephalin (a natural painkiller) than basal or reflex tears.

The limbic system is involved in production of basic emotional drives, such as anger, fear, etc. The limbic system, specifically the hypothalamus, also has a degree of control over the autonomic system. The parasympathetic branch of the autonomic system controls the lacrimal glands via the neurotransmitter acetylcholine through both the nicotinic and muscarinic receptors. When these receptors are activated, the lacrimal gland is stimulated to produce tears.”

So pretty big words…and I’m not sure it actually answers it. Unless the production of these painkilling chemicals is just trying to get the body back to a stable state and if you go overboard one way or the other it kicks in to help you release the emotion and bring you back to stability…but this is just my own surmisings!! I personally can’t really think of a time when I have cried purely for happiness…release of tension yes but not happiness – so there is possibly both a genetic and conditioned environmental reason for our tears!! 🙂