Have you ever wondered why when you touch a lit stove you feel the sensation
of heat, or why when you've cut your finger you feel pain? Probably not.
You were probably thinking something more like, OUCH! But, these sensations
are transmitted by the nervous system, the communication link between the
outside world, your brain, and the rest of your body.
Information from the outside world is carried to and from the brain through highways and networks of nerves. Nerves are simply tube-like extensions between nerve cells. The different information carried on each nerve is due to the special way they're fired along. Nerves are one way streets. For example, messages carried from the heart to the brain cannot be returned unless they're on different nerves. Nerve cells generally all have similar structure. They have a cell body with branched dendrites and an axon sprouting from it. Axons can range widely in length, from an inch to yards.
There are different types of nerves in the human body. Sensory nerves are the nerves that take information from the body's sense organs and receptors to the central nervous system (CNS). The CNS is made up of the spinal cord and the brain. The information processed in the brain is put forth to muscles and glands through motor nerves. The nervous system is split into sympathetic nerves and parasympathetic nerves. These two usually counteract each other. Sympathetic nerves usually give the body preparation for emergencies such as bodily harm or sharp temperature changes. Parasympathetic nerves, on the other hand, usually maintain the body's smooth operation with the least amount of energy output.
Quadrapaledrics and those otherwise paralyzed in parts of the body all suffer due to injuries to certain nerves. Nerves in the CNS cannot be renewed. This is why people stay paralyzed.
A synapse is what interconnects all the neurons throughout the circuit. Any neuron may receive thousands of synaptic connections and in response send out that many. Since the human nervous system has billions of neurons, it is very difficult for people to study and map the maze.
There are different causes for neural disorders. Some may be inherited while others are infectious. Alzheimer's disease is a disease that may result in memory loss and problems in thinking straight. Tetanus is an infectious disease that is caused by the bacterium Clostridium tetani invading an open wound. It results in symptoms of stiff jaw muscles, giving it the nickname of lockjaw. Other disorders and diseases such as epilepsy and leprosy are equally harmful to the human body. It's a shame the nervous network cannot always redeem harmed neurons or prevent these conditions.
As the Sand Man makes his call and hits his bag over the tired head of
a sleepy child, visions of sugar plums, circuses, and other fantasies begin
to dance in their heads.
A dream is a kind of mental experience in which, although the body is asleep, the brain is very awake. Dreams seem as real as if the event is actually happening, and most people dream 1 to 2 hours a night even if they claim that they do not dream at all.
A machine called an electroencephalograph is a device that helps scientists study the actual physical process of dreaming. This instrument records the electrical impulses sent off by the brain. The brain patterns vary according to the activity it is carrying out, so different patterns appear in light or deep sleep or in a dream. Dreams also affect the body's internal processes. An exciting dream will cause the dreamer's heart rate to beat faster and blood pressure to become higher. In research, scientists monitor the times when people are dreaming and wake them before it has ended in hopes that they will recall the dream.
Everyone passes through periods of light and deep sleep. For most, each period lasts from one and a half to two hours. At the end of each period a person has a session of dreaming. Research has also shown that people have a need for dreams, and if not allowed to dream, are nervous, easily upset, and hungrier.
Nightmares, similar to dreams, are also experienced by everyone. But unlike dreams, they are long and frightening and appear to be very real. Nightmares occur when the monsters, wild animals, witches, goblins, and dangerous people come out to haunt.......
They may involve running from danger, or falling from a cliff or out of a tree. Nightmares usually occur during the last part of sleep when a person is under stress or undergoing traumatic events.
Rapid eye movements, or REMs are also linked to dreams. Researchers have found that during a dream a person's eyes move back and forth rapidly behind closed lids, almost as if the person were watching their dream on T.V. Scientists have also found that dreams serve a purpose. Dreaming helps people live normal lives because they are able to work out their emotional problems through the dreams. Others think dreams strengthen memory and still others believe that dreams remove ridiculous things from our minds so we act sensible and clearly.
No one really knows what causes a yawn. You yawn because you are tired
or bored. Often, if someone near you just yawned, you might yawn also.
You don't usually yawn when you are exercising, or are angry or excited.
Yawns are probably caused by the body's need for extra oxygen to help keep
you awake. But, that doesn't explain why if one person in a room is yawning,
it becomes contagious, and the whole room will end up yawning also. The
next time you are sitting in the classroom listening to an extremely boring
lecture and you yawn, your teacher might indignantly say, "Am I that
boring?!" Now, you can promptly give the scientific reason for the
yawn and get out of being in trouble.
Night has come and it's time to go to sleep. The children are tucked
in and all is quiet. Everyone in the house is falling into a pleasing slumber,
when suddenly, a loud, ferocious noise radiates from a soundly sleeping
father. People who snore breathe through their mouth instead of their noses.
Snores occur when the soft part of the mouth and the throat wiggle and flop
as air goes in and out. Most people snore only when they are lying on their
After so rudely being awakened, all the troops gather together to push the snoring being on its side, and they sigh as the horrendous noise ceases... at least for the moment.
As a five year old child sits intently studying the cards before him,
he quizzingly tries to remember where the other "frog" was hiding
in the rousing game of Memory he and his comrade are playing. But, how do
we remember things? That question is very difficult to answer, but some
scientists think that individual nerve cells have chemically coded information
within them. Others believe that memory is a result of some sort of permanent
change in structures of the nerves, like the dendrites.
Scientists also believe that areas of the cortex appear to be involved in memory. When these areas are excited by a weak electrical current, the person relives past experiences. The electrical impulses force the brain to reproduce experiences stored from the past. It is also known that injury to certain areas of the brain will result in a temporary or complete loss of memory. This ailment is known as amnesia.
The brain is the most complex organ in the human body, and we are just beginning to understand the complex processes of thought, expression, consciousness, and memory. Studying this system will prove to be a challenge to scientists as long as they continue to "wonder" at all.
You get hiccups when something weird happens to your diaphragm. Your
diaphragm usually has a regular rhythm of tightening and relaxing when your
breathe in and out, but sometimes the diaphragm snaps tight in a spasm.
When the diaphragm is tight, air usually goes into the lungs, but when there
is a spasm, a tiny flap at the back of the throat covers the opening of
the windpipe and prevents the air from going down. The "Hiccup"
sound is made when air hits this tiny flap, also known as the epiglottis.
No one really understands what causes these spasms. They can occur from laughing too hard, or swallowing too fast. Although hiccups usually stop after awhile, most people can't stand them even for a minute, and have invented many curious ways to rid themselves of this ailment. Among them are breathing into a paper bag, getting a big scare, swallowing water while holding their breath, and hanging upside down while drinking a glass of H20.
In most countries, burping at the end of the meal or in public is considered
rude and uncouth, but in some places such as India, burping at the end of
a meal is considered a sign of satisfaction after eating a pleasing culinary
delight. But in any instance, burping is the body's way of getting rid of
too much air or gas in the stomach.
When you eat and drink you swallow air. As your stomach begins to digest the food, the air and gases rise as bubbles, and pop, just like the carbonated bubbles in soda. This causes pressure against the stomach and the air pushes into your esophagus. It bursts out in a loud, resounding burp, or as the scientists call it, an eructation.
When it's cold outside, or you are frightened by a herd of ghouls, witches,
and goblins, you get little bumps all over your body called goose bumps,
or goose flesh. If your examine those bumps, you will see hair coming out
of the middle of each one. Each hair is in a follicle with a muscle attached.
Usually those muscles are relaxed, and the hairs lie flat, but if you are
cold or scared, the muscles tighten and the hairs stand up.
Many researchers believe that millions of years ago, primitive people who descended from apes, were covered with thick hair. When the goose bumps formed on them, the hair stood up and the warm air from the body was trapped to keep the person warm.
Images copyright PhotoDisc, Inc., 1996.
Images copyright T/Maker Company, 1996.
New Book of Knowledge, 1987. Grolier Inc.