Cries

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The question of the function or origin of emotional tears is still open. Theories range from the simple such as response to inflicted pain to the more complex including nonverbal communication in order to elicit helping behaviour from others.
No other species on the planet can shed emotional tears. As a result scientists believe that crying must be caused by some especially complexhuman behaviour. Over a hundred years ago Darwin said that crying was used to attract attention, particularly in children. He said that tears act like a red flag to signal distress. 

Recent psychological theories of crying emphasize its relationship to the experience of perceived helplessness. From this perspective, an underlying experience of helplessness can explain why people cry in most situations; for example, a person may cry after receiving surprisingly happy news, ostensibly because the person feels powerless or helpless to influence the events that are taking place.

Crying or weeping (physic tears): is increased lacrimation due to strong emotional stress, depression or physical pain. This practice is not restricted to negative emotions; many people have been known to cry when extremely happy or when they are laughing. 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. The limbic system is involved in production of basic emotional drives, such as anger, fear, etc. The limbic system also has a degree of control over the autonomic system. This is more specifically the hypothalamus. It is the parasympathetic system that controls the lacrimal glands. Acetylcholine is the neurotransmitter specific to both the nicotinic and muscarinic receptors. It is when the receptors are activated that the lacrimal gland is stimulated to produce tears.