Why does grief or great happiness produce a watering of the eyes - what is the evolutionary advantage?
345826
Not everything has to be an adaptation, but assuming it is, there is likely an adaptive value to demonstrating emotion in a social animal such as humans. I don't know the specific answer to your two questions, but you might start with Darwin's "Expression of Emotions in Man and Animals", he discusses it there, I'm sure there's been work since.
288385
The psychic tears (or emotional tears) require an emotional response, or trigger to be activated. This response can be caused by an outside source, either pain or loss of love, etc., or from an inside source (self-realization of one's life and others). When emotions affect us, the nervous system stimulates the cranial nerve, in the brain and this sends signals to the neurotransmitters to the tear glands. Thus, we cry .The largest tear gland, the lacrimal gland produces the tears of emotion and reflex. Many believe that the body, in times of emotional stress, depends on this gland to release excess amounts of chemicals and hormones, returning it to a stable state.
19027
I think the scientific explanation is that this is a behavior trait that is hard-wired into their brains through the wonders of natural selection.  When animals are born (including people), their brains (and actually their entire physical bodies) are pre-programmed to do certain things.  They eat when they're hungry.  They "feel" hunger when they haven't eaten in a while.  They run when they're scared.  They feel scared when they see, smell, hear, or feel certain types of things.  Their hearts beat.  Their eyes blink.  They sleep when they're tired.  Having these characteristics gave them the ability to survive as a species and be around today to be observed by us.  Animals who had hearts that didn't "know" to beat automatically didn't last long.\n\nSo flying south for the winter is an instinct that allowed birds to survive.  The many birds who lacked that instinct had more difficulty surviving.
1036512
Most mammals will produce tears in response to extreme pain or other stimuli, but crying as an emotional reaction is considered by many to be a uniquely human phenomenon, possibly due to humans' advanced self-awareness. Some studies suggest that elephants and gorillas may cry as well.
572315
I think many people do feel that their heart is an indicator of emotions like joy, fear, love, anticipation, gloom, etc. And certainly medicine has found a correlation between long-term stress and heart condition. How the heart detects these conditions, what form its responses take (rate, volume, pressure?), and how we perceive those responses sound like interesting fields of inquiry which some biologists are investigating. See the refs.
859252
Sure. Why not? Any tears you cry will rapidly dissolve into the surrounding water, but tears can be leaving the tear duct.
718704
Well, crying over a death probably combines a number of feelings. \n\nYou're sad about that empty spot in your life, now that the person is gone and you can no longer be with them.\n\nYou're sad for the dead person, that they didn't live longer or perhaps that they suffered when they died.\n\nYou're sad for the person's family, who now is left without that person's presence.\n\nYou're sad over death in general -- the fact that people even have to die at all.\n\nYes, it's possible to be upset more for your own loss than anyone else's, or to let yourself wallow in grief without letting yourself adjust and heal over time, but in general I would be more worried if you didn't cry or feel loss over someone's death. \n\nIt's natural and healthy to be sad.
1035946
your eyes cannot handle the amount of impurities in the waters of the ocean or pool... what make your eyes burn is them trying to clean all that stuff up.. Its ok if you do it for a little bit, because the eyes are one of the fastest healing tissues in the body.. but you dont want to do it often enough that you damage the tissue permanently
504075
My guess it's a response to stress.  Sight is the main sense in people lucky enough to have it and we rely too much on it.  If shocked, it might be good to have a clear sight in case something comes your way (imagine you're a caveman and big sabertooth cat is cominagetcha)
478894
It's sad when people die because we're losing one of our loved ones. It's nice that they go to heaven, but the thought of never seeing them again is sad. We're grieving over our loss.
135816
Why?  Evolution.\n\nWhat purposes do they serve?  (ah, glad you asked...)\n\nThey keep sweat out of our eyes.\nProvide some amount of shade from the sun.\nAre used to communicate emotions through facial expressions.\n\n... and more!\n\nEyebrows!  I love 'em so much, I've got two!
1008692
It is therapeutic. It allows endorphines to be released into your system that provide a calming and numbing effect. Once you are calm, the pain of the sorrow begins to ease. \n\nThis is why women who are going through tough times with a spouse, friend, kids, life will sometimes rent a good "cry" movie. Something about crying seems to just "get it all out" and then you can move on with life the next day.
225058
The flowers, plants, animals that live in the wild, the soil needs a lil water from time to time. So allot of benefits come from rain. Now if it rains for a week and floods everywhere like it is here now I wanna know what benefits comes from that? Besides wasting gas to go the long way to town, work, run errands etc...
814403
its because when we are sad our facial muscle's shape become  distorted therefore squeezing the tear glands..
445776
This site answers your question perfectly:\n\nhttp://www.nlm.nih.gov/medlineplus/ency/article/002914.htm\n\nThey give several reasons for this including dehydration, post nasal drainage and overproducing tears.  Check out the link above....
528704
This time of year simple allergies can cause it.  There are several products on the market for this.  I myself use "Allergans" liquid-gel tears.  The thicker fluid of this product stays with you longer and definitely is refreshing to your eyes.
927932
Hi there,\nI think you are more inquisitive about emotional aspects of " pain" rather than what is called in medical/physiological jargon as 'nociception'.\nNociception is the sharp stinging or burning sensation you feel when you poke ur fingertip with a pin, or after a surgery, fall, fracture or even the feeling sensed in a frost bitten foot ! This is actually a sensation imparted to the brain by Potassium ions released locally from the cells of the injury site, acting through nerve fibers that travel all the way to the " thalamus" in the brain. \n\nThe regions in and around thalamus, called the " limbal circuit"  as well as a few other glandular structures are those that involve the " emotional " aspect of pain. Signals travelling to and from these regions release stress hormones and a vast array of brain chemicals like Gaba, Glutamate, Serotonin etc. \n        Stress hormones like Norepinephrine and cortisol act on various body organsystems and this results in the physical manifestations of deep pain/emotional upset, viz. a pounding heart, depressed mood, that heart-breaking feel, loss of appetite,  and general uneasiness. The brain's  limbic circuit sends signals to facial muscles and the tear glands in the eyes.  \n        When these signals are powerful enough, a person bursts into tears ! Violent contractions of muscles of the face (around eyes, cheek etc) can itself stimulate the tear glands. Thats why you tend to shed tears even when you laugh.\n       The stress hormones released during a painful experience is a way of nature to strongly  imprint the experience in mind so that the organism will "remember " to avoid such experiences or encounters later if possible. \n                 Crying is a way to communicate the agony to a similar organism in the vicinity, even though shedding  tears may or may not be a part of " the act". But over millions of years of evolution, primates like humans have learned to cry  in private just to give vent to the emotions. Mammals like Elephant, cow, deer etc "cry" as part of social behaviour.\n           It has been proven through extensive research that painful situations create a much lasting memory than happier moments.( a good reason to reintroduce corporal punishment in schools!).\n\nSo long then,\nbye...!