As Tears Go By

A look at animal and human tears

Children cry easily and even after a minor bump or hurt will shed tears. Adults may feel pain, cry and scream when hurt, but unlike children will not shed tears. An adult’s tears are associated with emotions or may be caused by some disorder, an eye infection or irritation, but not pain. And animals? They, too, have lacrimal (= tear) glands and can have watery eyes as the result of an infection or as part of a physiological control to remove excess salt from the body, but apparently not in connection with an injury. Sea turtles and a few other reptiles remove excess salt not only via their kidneys but with the help of their orbital eye glands as “white tears of saline” that drip out of their eyes.

Although human tears are not white, but watery, transparent and very slightly sticky because of mucins in them, they too contain salt  – as do, in fact, the tears of all land vertebrates that may not ‘shed tears’ but use the lacrimal fluid to lubricate their eyes and keep the cornea moist. Chemically tears are mostly water (ca. 98%); and apart from salts the lacrimal fluid contains a cocktail of amino acids and proteins, antibacterial enzymes and minute quantities of stress hormones. A tear’s chemical composition depends on the cause of its shedding and varies on whether the tear’s function is to wash out dust from the eye, to fight off irritants such as fumes (smoke or onions come to mind), to lubricate the eye’s surface, and as a response to physical pain and emotional upheaval. The autonomic nervous system through its parasympathetic branch governs the production and release of tears from the lacrimal glands, which are located in the upper region of the eye’s orbit. The tears are stored in the lacrimal sac near the nasal corner of the eye; from there the fluid via lacrimal canaliculi is released into the eye upon a signal from the parasympathetic nerve’s acetylcholine transmitter. In healthy individuals, there is a constant release of minute quantities that are distributed with each eye blink across the cornea, but of greater amounts if required. Excessive fluid is drained through the nasolacrimal duct and causes the ‘sniffle’ during weeping.

Basal tears are continually-produced via the 5^th cranial nerve’s innervation to keep the eye’s cornea moist and to prevent bacterial infections. In humans, about 0.75-1.1 ml of the liquid is produced each day. Reflex tears are produced when the eye is irritated, and through their copious amount and high water content function to remove the irritation from the eye. Psychic, also known as ‘emotional’  tears, occur in response to strong feelings, which could be sadness, but also joy, stress and  physical pain. Because these tears contain such natural painkillers like leucine-enkephalin and prolactin, it may explain the role of the parasympathetic nervous system and that “a good cry can feel relieving”.  But it does not explain why men shed tears less often than women, a fact that is often explained with the traditional roles men and women are expected to play in life (the advice “boys don’t cry” is a case in point).

The fourth reason for tears is related to diseases and the release of tears accompanying other activities (e.g. yawning). Although elephants have been described as shedding emotional tears, crocodile tears are not an expression of emotional distress, but the result of compression of a nerve that controls the jaw muscles during feeding. In humans suffering from Bogorad syndrome “crocodile tears” also accompany swallowing. Reference to tears can generate resolve (Churchill’s famous “Blood, Sweat and Tears” comes to mind); tears evoke empathy: children know that (and actors train to shed tears at will) and tears appear in poems and songs (the record “Tears on my Pillow” is in my collection) and who wouldn’t remember Marianne Faithful’s beautiful song “As Tears Go By” or Eric Clapton’s touching “Tears in Heaven” (which I heard it for the first time in Chile in 1993). I actually heard of people who shed tears when listening to it.

© Dr V.B. Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com, 2022. Unauthorized use and/or duplication of this material without express and written permission from this site’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to V.B Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com with appropriate and specific direction to the original content.

Yawning? 

I Hope It’s Never Happened Reading “Bioforthebiobuff”

At high school we had a history teacher by the name of Dr. L., who had spent 11 years in a Soviet prisoner-of-war camp before being released in 1955. He used to put the history book on the classroom’s desk, positioned himself comfortably on a chair near the side of the classroom and asked some of the best readers in class to take turns to read from the book. That’s how his lesson went. Although he can perhaps be forgiven for killing our interest in history by this behavior of his, his antics were also a cause of hilarity, especially when we noticed the regularity of his yawns and could predict when another big yawn of his would appear (silently counting: 14, 15, 16, 17, “yawn”!). But what made him yawn so much? Boredom, lack of sleep, or something else? And why is it so ‘contagious’? Mirror neurons perhaps?

The common view has always been that yawning was related to a lack of oxygen, a build-up of carbon dioxide and a room that was too warm and stuffy. Consequently, a call to open the window and let in ‘fresh air’, could often be heard in situations where people were seen to yawn frequently and appear sleepy. Yet, numerous studies have shown that lack of oxygen and carbon dioxide increases are by themselves not a cause of yawns. The situation is complex and although the amount of yawning appears to be correlated with boredom and sleepiness, it must leave us puzzled to notice that even after a good night’s sleep we wake up and then more often than not yawn upon awakening. Why yawn at that time? And cooling the brain in the morning or at other times by gaping wide: does it make sense? The idea that yawning is a component of thermoregulation has not yet achieved the acceptance it hoped to get.

If we examine objectively what happens during a yawn, we notice that it involves a wide open mouth and a long and deep inspiration of several seconds, sometimes accompanied by some soft vocalization during expiration. It is an involuntary behaviour that can be triggered by thinking and reading about yawning and/or seeing someone yawn. Yawning is communicative and is generally coupled with inactivity, lethargy and sluggishness (sometimes worry as well). To suppress the yawns can be difficult, especially when hindered to move as in boring meetings, lectures, and waiting rooms. And this actually gives us a clue: our bodies need us to stretch occasionally, to shake our arms and legs, to release tension.

The realization that yawning is a stretch response has been gaining attention ever since it was observed that when hemiplegic individuals that not normally can move their arms do move them when they pandiculate with an associated yawn. Yawning when pandiculating, i.e. stretching and thereby contracting and relaxing muscles, reduces muscular tension, is resetting and restoring the control over muscles, something that is critical for posture and movement and something that yoga instructors constantly emphasize. Obviously, the fact that the slow expiration following a yawn is associated with a sympathetic activation marked by an increase in blood pressure, suggests that at the start of the yawn it is associated with a sympathetic suppression that favours a parasympathetic dominance. This might also explain the observation of a paraplegic’s involuntary movement of its toes during a yawn.

Yawning must have ancient roots in the animal kingdom, for it can be observed in almost any animal group and is not even restricted to vertebrates alone as this delightful recording of a yawning leech shows here . Lizards, frogs, toads and even fish can be seen to yawn and all of them are ectothermic (often referred to as ‘cold-blooded’). As such, they would not be expected to use the yawning response to cool their brains as has been suggested for mammals, but could find yawning useful in connection with stretching and therefore the restoration of muscle control. Yawning:  a kind of physical exercise without having to get up? I think that that is a distinct possibility.

© Dr V.B. Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com, 2021. Unauthorized use and/or duplication of this material without express and written permission from this site’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to V.B Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com with appropriate and specific direction to the original content.

The Worm that isn’t a Worm at All: the Ringworm

When my daughter still attended elementary school, she came home one day with a note from the teacher that as parents we should be aware that cases of head lice had been noticed at school. All parents were therefore advised to check their children’s hair and if the insects or their nits attached to hair shafts were present to take steps to eradicate them. Unsurprisingly, we found that my daughter had also been infected, which led their two slightly older brothers to tease and avoid her, with one of them taunting her with “you are contaminated” (a word he must have learned recently). However, that very boy sometime later developed a ringworm infection on his scalp and then it was I, who avoided play fights with him and warned his siblings not to get too close to him or share his towel or pillow or cap. The term “ringworm” didn’t sound too nice and they all wanted to see what it looked like. But when I could not show them anything more than an oval or circular reddish and coin-sized patch on the skin of their brother’s neck, they were disappointed and lost interest.

So, what is this “ringworm” all about? Signs that a person is infected by the ringworm condition are the roundish patch mentioned above with a slightly raised edge and the fact that it itches badly. Doctors will diagnose this as something they call “tinea” or “dermatophytosis”; a complaint, in other words, caused by a skin fungus that in humans goes by the name Trichophyton schoenleini or T. rubrum in tropical regions. These species of fungi feed on the horny protein, known as keratin, which the outer layer of the skin, but also hair and fingernails consist of. These fungi belong to a fungal division known as Ascomycota (formerly termed Ascomycetes) , a grouping of species that also contains the important baker’s and brewer’s yeast Saccharomyces cerevisiae, the edible and expensive morels and truffels and some feared (and annoying) filamentous fungi inside the lungs.

Ringworm species that can colonize the human skin can be found in the form of dormant spores in the soil, but they may also reach human hosts from wild as well as domestic animals. Animals usually have their own species like Trichophytum verrucosum in the case of cattle or T. equinum in the case of horses and Microsporum canis in connection with dogs. The ringworm fungi cause these animals to feel itchy, but the fungi can also infect humans and humans can infect animals. What all these ringworm fungi have in common is that they love moist and warm skin and knowing that, one way to beat them is to dry the infected areas thoroughly after bathing or sweating. Of course it is also important to change clothes regularly like scarves, hats, socks, etc. that would have been in contact with the infected areas, and to avoid sharing combs and hair brushes with others and to change pillow covers and bed sheets frequently. Additionally, some anti-fungal creams and lotions should be applied to the infected areas. Certain lotions like oregano and lemongrass oils may help as well. If untreated the ringworm patches may develop into bald and permanently hairless areas.

There are, of course, other skin conditions that itch, produce reddish patches, lead to flaky skins and are irritating, but need not be caused by a ringworm fungus at all. Often going under the general name “eczema”, the autoimmune disease psoriasis is sometimes mistaken for ringworm. However, psoriasis is not contagious. It is caused by white blood cells known as T-cells that erroneously turn against the body and attack the skin when the latter has been injured by a chemical irritant, insect bite, sunburn, certain weather conditions or when a person has been under severe psychological or physical stress. In the case of my son (see above), his ringworm condition was a just punishment for having been mean to his sister when she suffered from head lice. But in terms of stress, it was mostly us parents who suffered during the time we had to worry about head lice and ringworms.

© Dr V.B. Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com, 2021. Unauthorized use and/or duplication of this material without express and written permission from this site’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to V.B Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com with appropriate and specific direction to the original content.