My Science School

Sodium chloride – the most common type of salt – is in all your body’s fluids: blood, sweat, and (yep) tears. Your tears contain a little less than one percent salt.

Tears contain greater quantities of water along with other organic and inorganic chemical components like mucin, lipids, lysozyme, lactoferrin, lipocalin, lacritin, sodium and potassium. The salinity of tears is attributed to the presence of salts of sodium and potassium.

This salinity of tears along with the presence of enzymes like lysozyme is responsible for their antimicrobial activity. Basal tears have a salt content similar to blood plasma. The salinity of basal tears disturbs the osmotic balance of bacteria and keeps the cornea in a healthy microbial-free environment. The mineral content of tears also nourishes the tissues associated with eyes. Saline nature of tears also indicates our evolutionary descent from marine organisms.

 

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Chickens have terrible night vision, but they’re capable of seeing colors – including vibrantly purple ultraviolet colors – that humans cannot. Researchers think chickens and other birds inherited their visual capabilities from their dinosaur ancestors. Because most dinosaurs weren’t nocturnal (active at night), they developed exceptional color perception and motion – detection vision for hunting a broad daylight.

 Chickens have very few cones, and they are not especially sensitive.  This difference between rod to cone ratio and the light sensitivities of cones in birds vs. mammals is explained because mammals all but disappeared from evolution long ago, and the only types of mammals that survived were nocturnal and insect eaters.  Mammals that survived this evolutionary bottleneck re-developed colour vision after millions of years, but since we evolved our cones from a different starting point than birds (they evolved from dinosaurs, and never spent millennia as nocturnal creatures), we developed our colour vision a little differently.  It’s another case of convergent evolution like whales and dolphins evolving to look like fish, because that’s the body type that works best in the water.

 

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Brown Eyes: Brown eyes are the most common eye color in the world with over 55% of the world's population having brown eyes. Brown eye color is a dominant genetic trait, and is created by the presence of melanin in the eye. Brown eyes are typically darker than other eye colors, and they may even appear black in certain individuals.

Hazel Eyes: Hazel eyes are similar to brown eyes, although they are typically lighter in color, and have more of a green-yellow tint. Hazel eyes have a higher concentration of melanin (pigment) around the eye's border, which can result in a multi-colored appearance that varies between copper and green depending on the lighting. Most people estimate that around 5-8% of the world's population has hazel colored eyes.

Blue Eyes: Blue eyes are genetically recessive and therefore much less common worldwide. Blue eyes are formed by the absence of pigments in the eye, where the blue color is formed by the scattering of light as it's reflected off the iris. It's estimated that approximately 8% of the world's population has blue eyes.

Green Eyes: Green eye color is often confused with hazel eye color, yet is entirely separate and distinct. Green eye color is the rarest color found around the world, and it is estimated that only around 2% of the world's population has green colored eyes. Green eye color is a result of a mild amount of pigmentation in the eye with a golden tint. When combined with the natural blue scattering of the eye, the colors mix to give a green appearance.

Silver Eyes: Silver eye color is also quite rare, although many consider silver eyes to be a variation of blue eye color. Like blue eyes, silver eyes are the result of a very low amount of pigmentation in the eye, which reflects a gray-silver appearance.

Amber Eyes: Amber eyes show off a yellow-copper tone, which results from the yellow colored pigment lipochrome. Amber eye color can range from golden yellow to a more copper tone.

 

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Sometimes, a person’s melanin pigment doesn’t spread evenly to each iris. Which can lead to one eye being darker than the other or even splashes of color in each iris? This extremely rare condition – known as heterochromia – doesn’t affect a person’s vision.

Heterochromia can be either present from birth (congenital) or acquired. Most people will have someone else in their family with the same condition, although if it develops at an early age it’s still considered to be congenital.

Acquired heterochromia can occur either from injury or illness, but won’t be the cause of any difficulty with vision. If any parts of your iris does change colour make sure you visit an ophthalmologist, just to be on the safe side.

Your eye colour is set by a variety of genes, but heterochromia occurs due to the concentration and distribution of a pigment called melanin. Melanin is also important in determining what colour skin you have and is found in your hair too.

It’s known that blue eyes contain the lowest amount of melanin, whereas brown eyes have the most, and so heterochromia is caused from one eye having either considerably more or considerably less melanin than the other.

 

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Eyelashes have one main purpose -- protecting your eyes. They help to keep dirt, germs, and other stuff out of your eyes, which are very delicate and need to be kept clean! Our eyelashes also help us know when a foreign object is headed towards our eye – when they sense the touch of some dirt or dust, they quickly send us the message to shut our eye and keep out the invader! 

Like the hair on your head, eyelashes sometimes naturally fall out and naturally grow back, too. It takes approximately four to six weeks for an eyelash that has fallen out to grow back, although because you have so many, it’s unlikely you’ll ever even notice it was gone! And don’t forget – when an eyelash lands on your cheek, pick it up, blow it away, and make a special wish!

 

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Your retina is covered with millions of special cells called rods and cones that process light from the lens. Cones detect colors (people who are colour blind are missing cone cells for a particular color), while the rods process light information. Scientists can guess at how animals perceive vision by counting the rods and cones in their eyes. Cats, for instance, have eight times as many rods as humans but far fewer cones, which explain their excellent night vision and their relative color blindness.

Photoreceptors cells take light focused by the cornea and lens and convert it into chemical and nervous signals which are transported to visual centers in the brain by way of the optic nerve.

In the visual cortex of the brain (which, ironically, is located in the back of the brain), these signals are converted into images and visual perceptions.

 

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CORNEA: The eye’s protective, transparent cover, the cornea is similar to the protective glass on a camera lens. It bends the light entering your eye to pre – focus the image before it reaches your lens.

PUPIL: Muscles in the iris control this hole in the center, which, like a camera’s shutter, allows light to enter the eye and strike the lens. In bright sunlight, the pupil contracts to let in less light. In darkness, it opens wide to let in as much light as possible.

SCLERA:  The whites of your eyes, sclera from a protective cover about the size of a ping – pong ball.

LENS: Like a projector in a moving theater, the lens focuses light onto the retina. It’s suspended in a muscle that changes the shape of the lens to focus on objects near and far faster than any computerized camera.

OPTIC NERVE: This cable carries visual information from your retina to the brain. Your brain processes the information and translates it into what you’re actually seeing.

 

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Like all human beings, you have ‘’binocular vision’’, meaning both your eyes face toward the front and provide your brain with two slightly offset images. Your brain processes the differences in these two images to create a perception of depth, or a three – dimensional view.

In order to see 3D and with stereo depth perception your brain has to use the visual information from both eyes. If the two eye views are too different and cannot be matched up, the brain will be forced to make a choice. It will reject all or part of the information from one eye. The brain can ignore, suppress or turn off visual information it cannot use.

 

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Just like the shape of your nose and the color of your hair, your eye color is determined by the genes you inherit from your parents. Those genes determine how much melanin – a colored chemical matter – you have in each iris, which is the colorful part of our eye. The more melanin you have, the darker your eyes. Less melanin makes for lighter eyes, which is why fair – skinned people often have light blue or gray eyes.

Brown is the most common eye color. Individuals with brown eyes have more melanin present, and over half of the people in the world have brown eyes. People who don this hue are said to be very independent, self-confident and determined. You are known to be trustworthy, and when people look at you they get a sense of security and stability.

Green is the least common eye color, but it is found most frequently in northern and central Europe. People with green eyes are curious about nature, very passionate in their relationships with other people and have an overall positive and creative outlook on life. These people tend to get jealous easily, but possess large amounts of love.

 

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Chase dreams are one of several common dream themes, stemming from feelings of anxiety in your waking life. Flee and flight is an instinctive response to a physical threat in the environment. In such dreams, the scenario often features you being pursued by an attacker, an animal, a monster or an unknown figure, who wants to hurt or possibly kill you. Ask yourself who is chasing you, so that you can gain a better understanding and insight on the source of your fears and anxieties.



The pursuer or attacker who is chasing you in your dream may also represent an aspect of yourself. Your own feelings of anger, jealousy, fear, and possibly love, can manifest itself as the threatening figure. Next time you have a dream of being chased, turn around and confront your pursuer. 

If you are the one doing the chasing, then the dream may highlight your drive and ambition to go after something you want. Or perhaps the dream suggests that you are falling behind and having to catch up with everyone else.

 

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Falling dreams are quite common and can be linked to anything that is subject to falling or going up and down -- finances, stocks, status, relationships, expectations, etc.

• Your perspective, view, or outlook of something may have fallen or is not living up to what you thought it might be.


• May indicate you are taking risky chances and putting yourself in danger.


• Falling in your dream may symbolize failure or your fear of failure.


• May indicate you are taking risky chances and putting yourself in danger.


• You may be feeling overwhelmed or out of control.


• Falling in a dream may be a result of a physical movement of the body, a change in your level of consciousness or a change in your blood pressure.


• May be a reference to the fall or autumn season or something that happened or will happen then.

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Life’s going great. You feel like you have the freedom to accomplish anything!  A flying dream could indicate strong feelings of freedom and bliss, which can represent moving toward a higher state of awareness or connection with spirit.  It can also provide a broader perspective on your life by virtue of giving you a higher vantage point. For the most part flying dreams are very positive dreams that signify high exceptions that reflect your walking life. Though it can also hold a negative translation if you are having difficulty taking off.  These thrilling type dreams are fairly common and considered one of the top dream themes we get in our life time. Flying dreams can be extremely vivid as if we are superman for the night. 

 

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The Alpha stage is a period in which the body and mind prepare to relax and might be accompanied by daydreams and a hazy feeling that may make these visions feel like actual dreams. Some could also experience realistic physical, visual, or auditory events during this time. It is estimated that people take an average of 7 minutes to fall asleep, but we should not actually begin dreaming until much later during the sleep cycle.

About an hour and a half into our slumber experience, we enter REM, or the Rapid Eye Movement portion of rest. This is when the actual dreaming starts. It is at this level that the muscles in the body are at their peak rest, while brain activity peaks.

The REM stage may only be a few minutes long when a person first experiences it. Sleepers go through the various cycles several times in one night and REM should grow longer each time it comes up in the cycle. This should also dictate the length at which your dreams last, as they happen in real time.

 

On average, it should take approximately 90 minutes to start your nightly adventures. But how long it lasts depends on the amount of time you are able to sustain deep REM sleep so be sure to practice mindfulness and meditation techniques that promote deeper sleep!

 

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Because something is keeping the air from moving freely through the passages behind their noses and mouths. Maybe they have bad sleep posture, or maybe they’ve put on weight or have a sinus infection. Sometimes, snoring is brought on by age. Whatever the reason, snoring can get loud. A woman in England once snored loud enough to drown out the sound of a low – flying passenger plane!

Those who have enlarged tonsils, an enlarged tongue or excess weight around the neck are more prone to snoring. And structural reasons like the shape of one’s nose or jaw can also cause snoring. The snoring sound itself is a result of the narrowing of a person’s airway, which causes a throat vibration and the snoring sound. No matter the reason, 40% of normal adults snore regularly, whether they realize it or not.

 

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Scientists aren’t really sure. Studies suggest that dreams help us cope with painful memories. Dreaming might also make us smarter and more creative during our waking hours. So if you’re feeling drained, grabbing 40 winks – and a few vivid dreams – might recharge your brain.

Dreams facilitate memory consolidation. New things learned during the day are reinforced by the firing of the new neuronal connections at night. But people don’t generally dream about a task they learned.

Dreams occur when specific neuron networks are activated. This is evidenced by neurocognitive research showing that during sleep neural activity only decreases by 10%. Without the neuron connections constantly firing, connections may degenerate. And thus, dreams are non-functional side effects of activation of networks that need to be activated to help keep the brain intact.

 

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