My Science School

Plane cabins are pumped with air to simulate altitudes of around 7,000 feet (2 km) rather than sea level, and it takes 20 minutes or so for a plane to reach its cruising altitude and interior pressure setting. That means passengers typically experience a gradual decrease in air pressure at the beginning of a flight and gradual increase at the end, provided the destination airport is lower than 7,000 feet (2 km). That gradual change in pressure is similar to what you feel when cruising up or down mountain roads or riding up or down a tall building in a fast elevator. Behind your eardrums are small air-filled chambers that connected to your throat through tiny tubes. When the air pressure outside your eardrum changes, air moves through the tiny tubes to equalize the pressure inside your head. That movement of air creates a popping sensation. Sometimes, if you have a cold or allergies gumming up your noggin’s empty spaces, your ears won’t equalize quickly enough, causing louder pops and bursts of pain as air presses against your eardrum.

 

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Your ears do more than just hear your brother’s burps and act as earring supports. They contain special organs that help you detect your motion, tell up from down, and keep you from tumbling when you trip. Whenever you move or tilt your head, fluid moving through canals in your inner ear interacts with tiny hairs along the canal walls, telling your brain that you’re in motion. When you spin in circles, the fluid spins right along with you. Stop and fluid keeps spinning, sloshing against the hairs and making your brain think you’re still spinning – which causes the feeling of dizziness.

 

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Doctors have a name for that fuzzy feeling in your head when you leap to your feet from a sitting position: ‘’orthostatic hypotension.’’ When you stand up quickly, gravity causes blood to settle in the lower parts of your legs and lower torso. Your body tries to equalize blood pressure to your upper torso, arms, and head, which results in a sudden drop in blood pressure and a few seconds of feeling faint. 

Many disorders can cause problems with blood pressure regulation and lead to dizziness when standing up. Categories of causes include

• Malfunction of the autonomic nervous system due to disorders or drugs


• Decreased ability of the heart to pump blood


• Decreased blood volume (hypovolemia)


• Faulty hormonal responses

Causes differ depending on whether symptoms are new or have been present for some time.

 

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You must have a ‘’photic sneeze reflex,’’ a condition that causes you to sneeze uncontrollably when suddenly exposed to bright light. About one in five people have it, although scientists aren’t sure why.

Researchers suspect that two important reflexes may play a key role in sun sneezing. The first is the pupillary light reflex. In this reflex, bright light entering the eyes sends signals along the optic nerve to the brain, which sends signals back to the eyes to constrict the pupils—a means of adjusting to differently lit environments. The second is the sneeze reflex, in which a cranial nerve called the trigeminal nerve detects a tickling in the nose and alerts the brain, which in turn stimulates the chest, nose, mouth and other muscles involved in sneezing.

 

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Roll onto your arm in your sleep and you’ll likely wake up to find it numb and lifeless, as if it wants to sleep in. Then comes the sensation of pins and needles. Contrary to what you might think, limbs don’t go limp simply because you cut off their blood supply when you lie on them wrong. Instead, you’re pressing on nerves and cutting off the limb’s communication with the brain. Roll off and the nerves go through a sort of ‘’reboot,’’ sending pulses to the brain that you perceive as that tingly feeling. The lazy limb comes back online in short order.

 

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Your tongue bristles with tiny bumps called taste buds: chemical receptors that interpret flavors and transmit that information to your noggin. Our sense of smell also greatly enhances the flavour of our food.

Taste buds have very sensitive microscopic hairs called microvilli. Those tiny hairs send messages to the brain about how something tastes, so you know if it's sweet, sour, bitter, or salty. The average person has about 10,000 taste buds and they're replaced every 2 weeks or so. But as a person ages, some of those taste cells don't get replaced. An older person may only have 5,000 working taste buds. That's why certain foods may taste stronger to you than they do to adults. Smoking also can reduce the number of taste buds a person has.

 

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Scientists have determined that the human tongue is attuned to several flavors: sweet, salty, bitter, sour, savory (think soy sauce), and possibly fat. Telling the difference between these tastes was crucial to our prehistoric survival. Bitter flavors, for instance, may have signaled a poisonous plant. Sour tastes indicated a spoiled supper. Sweet, savory, and fatty flavors were tired to foods with a lot of energy.

The ability to taste is so crucial to the act of eating that when we can't taste our food we just don't have the desire to eat as much as we usually do. Weight loss is common for people who can't taste or smell their food for whatever reason. For some of us this may be desirable, but for others it can lead to impaired immunity, poor nutritional status and the worsening of some diseases.

The ability to taste and smell our food is vitally important for our health and well being. For some people who may have a diminished sense of taste, using a flavor enhancer such as monosodium glutamate can help counteract the problem.

 

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Fingernails grow slowly – roughly a hair’s width a day – but that growth adds up over the long term. Let your grow wild and you might eventually beat the Guinness World Record set by Melvin Boothe, whose untamed claws reached a combined length of more than 32 feet (nearly 10 m).

Several factors affect the rapidity of nail growth. Fingernails, for example, grow faster during daytime than at night. In addition, fingernails grow at a greater clip in the summer, for the young, and slower for older people and in the winter. The middle, ring and index fingernails grow the fastest, while the thumb and little finger lag behind. 

 

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It should come as no surprise that gorillas, chimpanzees, and other higher primates closely related to humans have fingerprints. But if you look closely at a koala’s paws, you’ll see tiny swirling ridges on the skin of its fingers and toes. They’re fingerprints, and every koala has unique set. That means animal detectives would have no problem tracking down koala crooks!

The remarkable thing about koala prints is that they seem to have evolved independently. On the evolutionary tree of life, primates and modern koalas' marsupial ancestors branched apart 70 million years ago. Scientists think the koala's fingertip features developed much more recently in its evolutionary history, because most of its close relatives (such as wombats and kangaroos) lack them.

 

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Believe it or not, that armor plating at the tips of your fingers is made of the same stuff as your hair and skin, a protein called keratin. It’s also in the hooves and horns of animals.

Keratin forms the cells of your hair and skin, too. It also forms cells that are a key part of many glands and that line internal organs. Nails start growing under your skin. As new cells grow, they push old ones through your skin. The part you can see consists of dead cells. That’s why it doesn’t hurt to cut your nails. Fingernails grow about 3.5 millimeters each month. Those are the averages for healthy adults. Whether you’re getting proper nutrition and how well you take care of your nails can affect the growth rate.

 

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Humans evolved with flattened fingernails instead of the thicker, sharper claws found on most mammals. Researchers think that fingernails and toenails helped our ancestors climb trees, peel fruit, and use simple tools. And fingernails are still useful today! Their color and condition offer clues about your overall health. Nail polish turns them into fashion accessories. You use them to pop open the tops of soda cans. And nothing makes a better back – scratcher than a nice set of nails!

The primary function of a fingernail is to shield the fingertip, the distal phalanx and the surrounding soft tissues from injuries. It increases the sensitivity of the finger by acting as a counter force when the pulp of the finger touches an object. Furthermore, it helps in certain cutting or scraping actions, and acts as an extended precision grip for the finger.

The hard covering of toenails protects and fortifies the dense network of blood vessels, muscles and flesh beneath them.

 

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When you move or bend your fingers, you occasionally squeeze tiny air bubbles that form in the protective fluid around your body’s joints. Those popping bubbles create an audible crack.

Like all joints, they're the place where two bones come together to allow movement-we have them in our wrists, knees, and everywhere else we can bend. Tough, flexible tissues called ligaments hold them together. Joints are covered with a capsule filled with a special kind of liquid, called synovial fluid that acts as a lubricant as we move around; they also contain small amounts of dissolved gas, which is what causes that pop when we crack them. 

 

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You might think that playing in the pool or soaking in the tub makes your fingertips and toes waterlogged and soggy. Not so! The prune effect is caused by blood vessels shrinking just below the skin – an automatic reaction triggered by your nervous system when it senses long exposure to water. Scientists think people evolved this reaction to improve their grip and traction in wet environments. After all, pruny fingers make it easier to snag slippery fish.

When hands are soaked in water, the keratin absorbs it and swells. The inside of the fingers, however, does not swell. As a result, there is relatively too much stratum corneum and it wrinkles, just like a gathered skirt. This bunching up occurs on fingers and toes because the epidermis is much thicker on the hands and feet than elsewhere on the body. (The hair and nails, which contain different types of keratin, also absorb some water. This is why the nails get softer after bathing or doing the dishes.)

 

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Those whirls, swirls, loops, and arches on your fingertips (and toes, in case you didn’t know) are unique to you – even if you have an identical twin – and they remain unchanged throughout your entire life. In fact, the faint ridges known as fingerprints from before you’re even born. Fluids in the womb put pressure on your developing digits, which combined with your rate of growth and genetic makeup, create one-of-a-kind designs. Ah, you want to know the point of those fingertip designs (well, besides incriminating crooks who forget to wear gloves). Scientists have put forth all sorts of possible reasons. Fingerprints might magnify the hand’s ability to detect vibrations, for example, or improve our sense of touch. They also might work like tire trends to help us grip objects.

 

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Lots of them, although the exact number depends on your definition of ‘’thumbs’’. Apes and many monkeys have opposable thumbs just like us, while smaller primates, pandas, and koalas have thumb like digits and claws that help them grip plants and prey.

Gorillas, orangutans, chimpanzees, and bonobos belong to the same family of primates as humans, the Hominidae family?the family of great apes. Studies have revealed that great apes share 97 percent of their DNA, which explains the similarities they share with us humans. The anatomy of their hands, for instance, bears a striking resemblance to that of our hands. All have four long fingers plus an opposable thumb. Furthermore, all except for humans have opposable big toes as well.

Like us, all these species use their hands to hold tools, climb trees, move from one tree to another, gather food, build a dwelling place, and all this is achieved, despite the fact that they are quadrupedal, i.e., walk on all four limbs. If it was not for the much-touted opposable thumb, these species would have had a tough time trying to do something as simple as peeling a banana.

 

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