Why do we Produce Tears when we Cry?

April 30, 2016 / Humans / 0 Comments /
why do we produce tears when we cry

Tears seem to have no purpose when we cry. They make your eyes blurry, make your nose run and generally don’t do anything helpful. There seems to be no obvious evolutionary reason as to why we would produce tears when we cry, but we do. The reason we do this is actually because the part of the brain which controls emotion is closely related to the part which controls tear production, so when one triggers, so does the other, and I will explain this in greater detail.

 

Purpose of a tear

Tears are produced from the lacrimal gland (a little gland you can see if you gently pull down your upper cheek) to lubricate the eye, provide nutrients to the eye and keep the eye clean. There are 2 types of tear which attract most attention in research – the basal tear, which is something you produce all day long, and is there to simply maintain the eye, and the reflex tear, which is produced to wash out irritants (such as those from onions). However, there is a third type of tear- the psychic or emotional tear, which is the kind of tear produced at times of heightened emotion. This tear is different from the previous 2 because it doesn’t require a physical stimuli, and its purpose is not obvious. It also contains more protein, manganese, potassium, prolactin and serotonin than the other 2 types of tear.

 

Emotion in the body

Emotion is a complex and broad aspect of human biology. It is mainly controlled in the limbic system (see diagram to the right), and a part of this system called the hypothalamus plays a very important role in Image of limbic system in brainthe expression of emotion such as laughing out loud. During times of heightened emotion (either happy or sad), this part of the brain is particularly active. Two important neurotransmitters used in this region of the brain are acetylcholine and serotonin, and so production/ activity of these neurotransmitters in increased during times of heightened emotion.

In addition to this, times of heightened emotion often are accompanied by some form of stress response, particularly is you are sad, angry or scared. The stress response (also sometimes referred to as the ‘fight or flight’ response) causes a number of hormones to be produced including prolactin, growth hormone, cortisol and a chemical called norepinephrine (also known as noradrenaline) which acts as both a hormone and neurotransmitter. 

 

A closer look at the lacrimal gland

Both acetylcholine and norepinephrine are both known to be potent stimulators of the lacrimal gland. In addition to this, prolactin and a hormone called adrenocorticotropic hormone (ACTH), which stimulates the production of cortisol also influence the lacrimal gland, but to a lesser extent than acetylcholine and norepinephrine.

With all of these lacrimal stimulating chemicals being produced there is little wonder that tears are produced in times of heightened emotional situations, almost by accident.

 

Do tears when crying serve a purpose?

Tear production when you cry seems to have no real biological significance, and it would appear that they are produced almost by accident. However, we are very social beings, and understanding others feelings and emotions is a vital part of our success as a species. Crying very clearly shows your emotional state, and helps to communicate to people around you how you need to be treated and how you are feeling. This in turn will help build bonds and enable a swift recovery from the cause of distress, which only makes for a stronger community. So no, they appear to have no physical importance like the reflex or basal tear, but it is possible they have a social importance.

 

Summary

The emotional or psychic tear is very different from the other 2 types of tear, both in why it is produced, and what it does. At times of heightened emotion the brain releases a number of neurotransmitters and hormones as part of an emotional and stress response. Many of these neurotransmitters and hormones are also activators of the tear gland, and so can stimulate the productions of tears, almost by accident.

Image courtesy of Yoshihide Nomura

This Youtube video will give an overview of the information found on the article tab. If you want to know more about the topic, or want to see where the information came from, have a read of the article after you watch the video.

When we get very sad (or very happy) the body produces a number of hormones to make us feel that way. By chance, these hormones also stimulate the tear glands, and when lots of these hormones are being pumped around our body, the tear glads get over stimulated, and produce too many tears.