Why do we cry when we're sad?

Crying or tearing, is known scientifically as lacrimation. Although most land mammals have a lacrimation system to keep their eyes moist, humans are the only animal generally accepted to cry emotional tears.

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.

(My Summary of Wikipedia: http://en.wikipedia.org/wiki/Tears)

the first bits of that made sense, but that last paragraph means nothing.

Thanks, but whats that on English? :D

I’m not sure science has a 100% firm answer as to why crying due to emotional distress makes sense, but what we do know is that emotional tears contain very high amounts of:

- Prolactin: a hormone that causes relaxation (and is also actually involved in the feeling of sexual gratification after sexual acts);

- Adrenocorticotropic: another — hard to say — hormone that reduces the feeling of stress;

- Leucine enkephalin: a very powerful natural pain killer.

(And reflex tears, caused by for example: dust getting into your eyes, do not contain very high amounts of these chemicals at all.)

In addition, crying can act as a very powerful body language signal that another human is in need of help and support.

cheers

yeahh, but I really dont think there is a scientific reason why we cry!
I mean, not everything is related to science.
Think about that.
Mybe scientist are wrong&
our instincts or feelings are produced by what we see or feel.
Not by Tear glands..

I’ve heard that it also releases toxins from your body and it is good for you to cry, I suppose, once in a while. Is this true?