arsalan667
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Q. Why do tears come in eyes when crying or after much laughter? And what is the reason for salty taste of tears?
A. The second question is more interesting but let us answer the first question first. There are tear glands beneath the eyelids of both the eyes. Eyelids take some liquid from these glands and give a wet wipe to the cornea with each blink of the eyes. If this phenomenon did not take place then cornea would become dehydrated ultimately resulting in blindness. Further, tears are necessary for removal of dust particles settling on the cornea. But more important is the protection against bacterial infection given by anti bacterial constituents in the tears. After cleaning the eyes with each blink, the tear drops drain into the nose through an internal tube where they are quickly evaporated by breathing. Crying or much leaguing brings pressure on the muscles above tear glands. These muscles in turn squeeze tear glands which result in flow of tears, some of which also come out of nose. A flow of cold air on the eyes during winter also causes constriction of the muscles above tear glands bringing tears in the eyes.
The mystery of salty taste of tears lies in the evolution of human beings. Millions of years ago living organisms came into existence in the seas first and after subsequent millions of years their descendents appeared on the land. In order to enable prehistoric marine creatures to live in salty water Nature made all body fluids including blood somewhat saline. That is the reason why any body fluid of human beings has somewhat salty taste. Just as blood is salty the tears are also salty.
Q. Why do we rub our eyes when we are tired?
A. Its because when we are tired, we dont produce enough moisture our eyes need, and rubbing them stimulates the tear glands. They are called lachrymal glands, one of which lies above each eyeball. They continuously produce tears that are necessary to keep the eyes moist and clean. As you blink about 15 times a minute, the eyelid washes tears across the eye. Surplus tear fluid drains down the tear ducts to the nose.
If your eyes feel dry and itchy several times a day you might have dry eye syndrome. This may be because eyes do not produce enough tears or because your tears are evaporating too quickly. Some people naturally produce more tears than others, and those with lower tear production are more likely to have eye irritations. Persistent dryness may be caused by a thyroid condition called Hashimotos disease, or a glandular disease called Sjogrens syndrome.
In most cases, however, dry eyes result from an inadequate fluid coming out of the lachrymal glands. This happens especially when you are tired. The best treatment is not to pick up kitchen knife and cut onions or have another viewing of tragedy-filled Titanic but to rub your eyes to activate the tear glands. Drinking plenty of water throughout the day might also help to keep your eyes lubricated.
Q. Why does ice-cream sometimes give you a headache?
A. Blame it on physics and psychology in equal measure. When ice-cream comes in contact with the roof of your mouth, blood vessels in the mouth contract in response to the fall in temperature. This is as physics would have it. The accompanying rise in blood pressure causes the vessel walls to stretch, which in turn stimulates pain receptors in the carnival nerves.
The physiological result is that you feel aching pain in the head a few seconds after your first mouthful. However, the pain is temporary and doesnt occur every time. Ice-cream headaches affect up to 30 per cent of people, and over 90 percent of people who also suffer from migraine. It is easily preventable. Stir the ice-cream into slush first, and try taking smaller mouthfuls. Dont hurry and be happy.
Q. What is the reason for yawning? And why is it considered infectious? Why do the ears appear to have become deaf during yawn?
A. First two questions are certainly difficult because even the experts do not have convincing explanations. Explanation of the third question, however, is quite simple. The process of hearing commences with the vibration of the eardrums. In order to allow the eardrums to vibrate freely it is essential that there is equal air pressure on both the sides of the eardrums. So Nature has arranged for as much air pressure on the inner side of the eardrums as the air pressure prevailing on the outer side to keep the eardrums neutral. When a person yawns, the internal muscles of the ears contract increasing the pressure from the inner side which in turn pushes the eardrums somewhat outward. Now in the outward dilated condition of the eardrums the sound waves are not able to vibrate the eardrums and so the sound is not heard till the eardrums come back in their original position.
The reason for yawning and infecting others into yawning is still a subject of research, but some aspects have been understood in the course of research on the subject. When a person is tired at the end of the day his muscles relax and the rate of breathing also slows down automatically. An adult person requires about 6 liters air per minute. About 15% of this quantity is consumed by the brain alone. It takes about 0.85 liter blood per minute to feed the oxygen in this air to the nerve cells of the brain. As the rate of breathing slows down the brain feels suffocation for the want of oxygen and sends public signal to the lungs to take a deep breath in the form of yawn. The yawn which follows lasts about 5.5 seconds. And if the brain is not satisfied with one yawn then some more yawns may follow. Repeated yawn are also a signal of approaching sleep. When asleep the body does not require much oxygen and also gets the rest it needs. Therefore, one does not yawn as much during the day time as late in the evening or in the night except when studying or compelled against will to do some boring task!
The researchers have not arrived at the conclusive explanation of why yawning is infectious. However, there is an interesting hypothesis. The control center for yawning in the brain sends signals for yawn on identifying fatigue, inertia, sleepiness or boredom. When we see somebody yawning this visual hint stimulates our brain to identify our own tiredness etc. if it has not already done and to send signal to lungs for yawning and there it is! Yawn !
Finally, an interesting piece of information: Whether during the day time or night most of the paratroopers of the army or the adventurous sky divers invariably yawn once or twice before jumping out of the plane to exercise muscles of the ears to be in readiness for low air pressure outside the aircraft.
A. The second question is more interesting but let us answer the first question first. There are tear glands beneath the eyelids of both the eyes. Eyelids take some liquid from these glands and give a wet wipe to the cornea with each blink of the eyes. If this phenomenon did not take place then cornea would become dehydrated ultimately resulting in blindness. Further, tears are necessary for removal of dust particles settling on the cornea. But more important is the protection against bacterial infection given by anti bacterial constituents in the tears. After cleaning the eyes with each blink, the tear drops drain into the nose through an internal tube where they are quickly evaporated by breathing. Crying or much leaguing brings pressure on the muscles above tear glands. These muscles in turn squeeze tear glands which result in flow of tears, some of which also come out of nose. A flow of cold air on the eyes during winter also causes constriction of the muscles above tear glands bringing tears in the eyes.
The mystery of salty taste of tears lies in the evolution of human beings. Millions of years ago living organisms came into existence in the seas first and after subsequent millions of years their descendents appeared on the land. In order to enable prehistoric marine creatures to live in salty water Nature made all body fluids including blood somewhat saline. That is the reason why any body fluid of human beings has somewhat salty taste. Just as blood is salty the tears are also salty.
Q. Why do we rub our eyes when we are tired?
A. Its because when we are tired, we dont produce enough moisture our eyes need, and rubbing them stimulates the tear glands. They are called lachrymal glands, one of which lies above each eyeball. They continuously produce tears that are necessary to keep the eyes moist and clean. As you blink about 15 times a minute, the eyelid washes tears across the eye. Surplus tear fluid drains down the tear ducts to the nose.
If your eyes feel dry and itchy several times a day you might have dry eye syndrome. This may be because eyes do not produce enough tears or because your tears are evaporating too quickly. Some people naturally produce more tears than others, and those with lower tear production are more likely to have eye irritations. Persistent dryness may be caused by a thyroid condition called Hashimotos disease, or a glandular disease called Sjogrens syndrome.
In most cases, however, dry eyes result from an inadequate fluid coming out of the lachrymal glands. This happens especially when you are tired. The best treatment is not to pick up kitchen knife and cut onions or have another viewing of tragedy-filled Titanic but to rub your eyes to activate the tear glands. Drinking plenty of water throughout the day might also help to keep your eyes lubricated.
Q. Why does ice-cream sometimes give you a headache?
A. Blame it on physics and psychology in equal measure. When ice-cream comes in contact with the roof of your mouth, blood vessels in the mouth contract in response to the fall in temperature. This is as physics would have it. The accompanying rise in blood pressure causes the vessel walls to stretch, which in turn stimulates pain receptors in the carnival nerves.
The physiological result is that you feel aching pain in the head a few seconds after your first mouthful. However, the pain is temporary and doesnt occur every time. Ice-cream headaches affect up to 30 per cent of people, and over 90 percent of people who also suffer from migraine. It is easily preventable. Stir the ice-cream into slush first, and try taking smaller mouthfuls. Dont hurry and be happy.
Q. What is the reason for yawning? And why is it considered infectious? Why do the ears appear to have become deaf during yawn?
A. First two questions are certainly difficult because even the experts do not have convincing explanations. Explanation of the third question, however, is quite simple. The process of hearing commences with the vibration of the eardrums. In order to allow the eardrums to vibrate freely it is essential that there is equal air pressure on both the sides of the eardrums. So Nature has arranged for as much air pressure on the inner side of the eardrums as the air pressure prevailing on the outer side to keep the eardrums neutral. When a person yawns, the internal muscles of the ears contract increasing the pressure from the inner side which in turn pushes the eardrums somewhat outward. Now in the outward dilated condition of the eardrums the sound waves are not able to vibrate the eardrums and so the sound is not heard till the eardrums come back in their original position.
The reason for yawning and infecting others into yawning is still a subject of research, but some aspects have been understood in the course of research on the subject. When a person is tired at the end of the day his muscles relax and the rate of breathing also slows down automatically. An adult person requires about 6 liters air per minute. About 15% of this quantity is consumed by the brain alone. It takes about 0.85 liter blood per minute to feed the oxygen in this air to the nerve cells of the brain. As the rate of breathing slows down the brain feels suffocation for the want of oxygen and sends public signal to the lungs to take a deep breath in the form of yawn. The yawn which follows lasts about 5.5 seconds. And if the brain is not satisfied with one yawn then some more yawns may follow. Repeated yawn are also a signal of approaching sleep. When asleep the body does not require much oxygen and also gets the rest it needs. Therefore, one does not yawn as much during the day time as late in the evening or in the night except when studying or compelled against will to do some boring task!
The researchers have not arrived at the conclusive explanation of why yawning is infectious. However, there is an interesting hypothesis. The control center for yawning in the brain sends signals for yawn on identifying fatigue, inertia, sleepiness or boredom. When we see somebody yawning this visual hint stimulates our brain to identify our own tiredness etc. if it has not already done and to send signal to lungs for yawning and there it is! Yawn !
Finally, an interesting piece of information: Whether during the day time or night most of the paratroopers of the army or the adventurous sky divers invariably yawn once or twice before jumping out of the plane to exercise muscles of the ears to be in readiness for low air pressure outside the aircraft.
