Watching an old episode of CSI NY (now known in our house as “CSI Implausible”) I came across an interesting titbit of information. Apparently there are three different sorts of tears:
- Basal tears: In healthy mammalian eyes, the cornea is continually kept wet and nourished by basal tears. They lubricate the eye and help to keep it clear of dust. Tear fluid contains water, mucin, lipids, lysozyme, lactoferrin, lipocalin, lacritin,immunoglobulins, glucose, urea, sodium, and potassium. Some of the substances in lacrimal fluid fight against bacterialinfection as a part of the immune system.
- 2. Reflex tears: The second type of tears results from irritation of the eye by foreign particles, or from the presence of irritant substances such as onion vapors, tear gas or pepper spray in the eye’s environment. These reflex tears attempt to wash out irritants that may have come into contact with the eye.
- 3. Crying or weeping (psychic tears): The third category, generally referred to as crying orweeping, is increased lacrimation due to strong emotional stress, suffering 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 leucineenkephalin (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.
[the above details from Wikipedia].
Fascinating, isn’t it?
I cry easily these days. It drives me nuts. The trouble is, when you start to cry people stop listening. As though it’s your brain that’s running, not just your eyes! Bah.