Reflexes
If you touch something very hot, your hands pulls away almost instantly, without waiting for your brain to tell it to. This is an example of a reflex - a rapid reaction that helps to protect you from injury. A massage flashes from your hand to your spinal cord - the bundle of nerve cells running down your body. The message is then passed straight to motor nerves, which make your arm muscles contract.
Reflex actions happen automatically, and often do not involve signals from the brain.
Deliberate actions - such as picking a paper, are triggered by signals from the brain.
Sensitive parts
All over your body, you have nerve ending that give you information about the things you touch. Instead of being spread out, they are concentrated in places where the sense of touch is most useful. The parts of the body that have the most nerve endings are drawn enlarged. The most sensitive parts are the mouth and fingertips, while the least sensitive are the backs of the arms and legs. You can prove this by closing your eyes, and asking a friend to touch your skin gently in sensitive areas with a pencil or paintbrush.
The gentle touch
Extra sensitive hands and fingertips help us to adjust our grip when we pick things up.
Tag :reflexes
Saturday, January 5, 2008
Wednesday, December 26, 2007
All in the mind
Your brain is divided into three main parts. Two of them called the brain stem and the cerebellum, control essential processes such as breathing, and keep all the parts of your body working together. The third part is much bigger, and allows you to sense things, think, and make your body move.
Brain functions
Seeing the world : Several areas of your brain are involved in interpreting signals from the optic nerves in your eyes.
Tuning in : The area that deals with interpreting sounds, called the auditory area, receives signals from nerves in your ears.
Fine control : Whenever you make complicated movements, for example when using a keyboard, the part called the premotor area helps to control your muscles.
Thinking and understanding : The front of the brain is where thinking takes place. The ability to think makes us aware that we exist. The two side work in slightly different ways. In most people, the "right side" deals with shapes and feelings.
Feeling your body : The area of the brain that receives signals from nerves in the skin is called the sensory area. It allows you to feel pressure, heat, cold and pain.
Making movement : The area of the brain that sends out signals telling muscles to contract when you decide to move is called the motor area.
Dealing with words : The speech area controls the muscles you use when you talk. A nearby part of the brain helps you to understand words when people speak to you.
Left side : The left side of the brain deals with logical matters, such as maths.
Tag :brain functions
Your brain is divided into three main parts. Two of them called the brain stem and the cerebellum, control essential processes such as breathing, and keep all the parts of your body working together. The third part is much bigger, and allows you to sense things, think, and make your body move.
Brain functions
Seeing the world : Several areas of your brain are involved in interpreting signals from the optic nerves in your eyes.
Tuning in : The area that deals with interpreting sounds, called the auditory area, receives signals from nerves in your ears.
Fine control : Whenever you make complicated movements, for example when using a keyboard, the part called the premotor area helps to control your muscles.
Thinking and understanding : The front of the brain is where thinking takes place. The ability to think makes us aware that we exist. The two side work in slightly different ways. In most people, the "right side" deals with shapes and feelings.
Feeling your body : The area of the brain that receives signals from nerves in the skin is called the sensory area. It allows you to feel pressure, heat, cold and pain.
Making movement : The area of the brain that sends out signals telling muscles to contract when you decide to move is called the motor area.
Dealing with words : The speech area controls the muscles you use when you talk. A nearby part of the brain helps you to understand words when people speak to you.
Left side : The left side of the brain deals with logical matters, such as maths.
Tag :brain functions
Friday, December 14, 2007
How do we remember things?
Scientist are still not certain how the brain remembers things, but they have produced a likely explanation. They know that each cell in the brain is connected to thousands of other cells via connection points called synapses. They think that the brain stores new information by forming new sets of connections between cells, it is as if the cells in the brain are constantly being rewired. At first, information is stored in your short-term memory. The information is then transferred into your long-term memory, which can store it for days, months or even years.
Lost forever
Unlike other cells in your body, the cells in your brain cannot be replaced when they get worn out. As a result, the number of cells in your brain steadily decreases as you get older.
Tag :memory
Scientist are still not certain how the brain remembers things, but they have produced a likely explanation. They know that each cell in the brain is connected to thousands of other cells via connection points called synapses. They think that the brain stores new information by forming new sets of connections between cells, it is as if the cells in the brain are constantly being rewired. At first, information is stored in your short-term memory. The information is then transferred into your long-term memory, which can store it for days, months or even years.
Lost forever
Unlike other cells in your body, the cells in your brain cannot be replaced when they get worn out. As a result, the number of cells in your brain steadily decreases as you get older.
Tag :memory
Wednesday, December 5, 2007
How do nerves work?
Most nerves cells have a long thread, called an axon, which works partly like a battery and partly like a wire. When the nerves is resting, the axon is charged with electricity, just like the terminals of a battery. When the nerves is triggered into action, the charge suddenly changes, creating a signal that flashed down the axon. The nerves that the signals pass along to tell muscles to contract are called 'motor nerves. The nerves that carry messages from sense organs to your brain are called 'sensory' nerves. Signals travel along nerves at about 360 km/h (225 mph), fast enough to travel from your brain to your toes in less than 1/50 of a second.
Tag :nerves work
Most nerves cells have a long thread, called an axon, which works partly like a battery and partly like a wire. When the nerves is resting, the axon is charged with electricity, just like the terminals of a battery. When the nerves is triggered into action, the charge suddenly changes, creating a signal that flashed down the axon. The nerves that the signals pass along to tell muscles to contract are called 'motor nerves. The nerves that carry messages from sense organs to your brain are called 'sensory' nerves. Signals travel along nerves at about 360 km/h (225 mph), fast enough to travel from your brain to your toes in less than 1/50 of a second.
Tag :nerves work
Thursday, November 29, 2007
BRAIN AND NERVOUS SYSTEM
Every second, whether you are awake or fast asleep, your is busy processing information. It receives millions of signals from all parts of the body, and its sends out signals that control the way your body works. These signals travel along nerves, bundles of cells that conduct tiny bursts of electricity. The brain itself contain more than 1000 billion nerve cells, and when they are busy these cells generate enough electrical energy to power a light bulb.
Unlike other cells in your body, the cells in your brain cannot be replaced when they get worn out. As a result, the number of cells in your brain steadily decreases as you get older.
Tag :brain
Unlike other cells in your body, the cells in your brain cannot be replaced when they get worn out. As a result, the number of cells in your brain steadily decreases as you get older.
Tag :brain
Wednesday, November 28, 2007
Sweat glands
Sweat is a watery fluid that helps to keep your cool. It is made by coiled glands that open onto the surface of your skin. The palms of your hands have more sweat glands than anywhere else, up to 500 per cm2 of skin (3250 per sq in).
Fingerprints
Sweat is a watery fluid that helps to keep your cool. It is made by coiled glands that open onto the surface of your skin. The palms of your hands have more sweat glands than anywhere else, up to 500 per cm2 of skin (3250 per sq in).
Fingerprints
Whenever you touch anything smooth, your fingers leave marks. These marks are called fingerprints. Fingerprints are made of sweat and body oils, and they are exact copies of the tiny ridges that cover your fingertips. Identical twins have matching fingerprints, but everybody else has their own unique pattern, which will resemble one of the basic patterns. Fingerprints are often used to identify people present at the scene of a crime. To find fingerprints, police scientists dusts the objects at a crime scene with a fine powder. This sticks to the sweat and oil that the fingers have left behind, making the marks show up. The police then see if the marks match up with the fingerprints of any of their suspects. There are four kinds of fingerprints :
- Arch
- Loop
- Whorl
- Composite
Tag :Sweat glands
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Tuesday, November 27, 2007
Hair
Hair protects your head and eyes from the sun. On other parts of your body, it helps you feel things brushing against your skin. And it helps to keep you warm. Most of a hair is made of dead cells.
Can hair really stand on end?
If you are cold or frightened, your hair may feel as if it is standing on end. A tiny muscle pulls on the root of each hair, levering it int a more upright position. As each hair moves, it pushed against the skin, making a 'goosebump'. Long ago humans had lots of body hair, and warm air would have been trapped in the little pits formed by goosebumps.
Tag :hair
Hair protects your head and eyes from the sun. On other parts of your body, it helps you feel things brushing against your skin. And it helps to keep you warm. Most of a hair is made of dead cells.
Can hair really stand on end?
If you are cold or frightened, your hair may feel as if it is standing on end. A tiny muscle pulls on the root of each hair, levering it int a more upright position. As each hair moves, it pushed against the skin, making a 'goosebump'. Long ago humans had lots of body hair, and warm air would have been trapped in the little pits formed by goosebumps.
Tag :hair
Skin ridges
These ridges are found only on fingers and toes, and on the palms of your hands and soles of your feet. They help to give you a good grip. The skin underneath them is extra thick for added protection.
Fingernails
Nails protect your fingertips (and toenails your toes), and also help you to pick things up. They are made from keratin, the same substance that makes hair. On average, a fingernail grows at a rate of about 1 mm (1/32 in) per week, four times faster than a toenail.
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These ridges are found only on fingers and toes, and on the palms of your hands and soles of your feet. They help to give you a good grip. The skin underneath them is extra thick for added protection.
Fingernails
Nails protect your fingertips (and toenails your toes), and also help you to pick things up. They are made from keratin, the same substance that makes hair. On average, a fingernail grows at a rate of about 1 mm (1/32 in) per week, four times faster than a toenail.
Tag :skin ridges
Tag :fingernails
Monday, November 26, 2007
Why are people different colours?
Skin gets its colour from chemicals called pigments present in skin cells. One pigment, called melanin, makes skin brown or black. Another, called carotene, gives skin a yellow colour. Pigments help to protect skin against damage by strong sunshine. People with pale skin have very little pigment and may easily get sunburned. If your skin is like this, it is important to stay covered up in strong sunshine, or to use sunblock.
Some people have more of a particular skin pigment than others. Apart from this, everyone's skin is the same.
Tag :skin colours
Skin gets its colour from chemicals called pigments present in skin cells. One pigment, called melanin, makes skin brown or black. Another, called carotene, gives skin a yellow colour. Pigments help to protect skin against damage by strong sunshine. People with pale skin have very little pigment and may easily get sunburned. If your skin is like this, it is important to stay covered up in strong sunshine, or to use sunblock.
Some people have more of a particular skin pigment than others. Apart from this, everyone's skin is the same.
Tag :skin colours
What is skin made of?
Skin is made of cells arranged in three main layer. The deepest layer, called the dermis, contains living cells, blood vessels and nerve endings that sense pressure, heat, cold and pain. Above this is a thin layer, called the epidermis, that produces new cells all the time. The new cells die as they are slowly pushed towards the surface, where they from a protective outer layer. Then they fall away in small flakes.
Flaking away
The surface of skin, magnified about 200 times, with flakes of dead cells forming.
Tag :skin made
Skin is made of cells arranged in three main layer. The deepest layer, called the dermis, contains living cells, blood vessels and nerve endings that sense pressure, heat, cold and pain. Above this is a thin layer, called the epidermis, that produces new cells all the time. The new cells die as they are slowly pushed towards the surface, where they from a protective outer layer. Then they fall away in small flakes.
Flaking away
The surface of skin, magnified about 200 times, with flakes of dead cells forming.
Tag :skin made
Sunday, November 25, 2007
SKIN, HAIR AND NAILS
Skin grows in step with the rest of your body, and although it constantly wears away, it is also replacing itself all the time. Like hair and nails, skin helps to protect your body from the out side world. It can do this because its surface is made of dead cells. These are very tough, and they from a barrier that shields the living cells underneath. Like the surface of skin, most of each hair is also made of dead cells.
Under the surface
Each part of your body has a different type of skin. For example, the skin on the back of your arm is covered with lots of hairs, although they may be too small for you to see. The skin on the palms of your hands and the inside of your fingers has no hair at all, but it does have lots of tiny ridges and invisible openings called sweat glands.
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Under the surface
Each part of your body has a different type of skin. For example, the skin on the back of your arm is covered with lots of hairs, although they may be too small for you to see. The skin on the palms of your hands and the inside of your fingers has no hair at all, but it does have lots of tiny ridges and invisible openings called sweat glands.
Tag :skin
Tag :hair
Tag :nails
Sneezes and hiccups
Breathing normally happens so smoothly that we hardly notice it. But sometimes it is interrupted by a cough, a sneeze, or by hiccups. Hiccups happen when your diaphragm contracts suddenly and air rushes into your lungs. Your vocal cords, membranes lying across your trachea that you use to talk, close, making a loud squeak. Coughs and sneezes clear out dust and other particles that get trapped in your airways and the lining of your nose. Colds cause coughs and sneezes for a few days, smoking can give people cough for years because some of the smoke gets stuck in the lungs.
Drops of moisture, dust and germs shoot into the air when you sneezes.
Breathing normally happens so smoothly that we hardly notice it. But sometimes it is interrupted by a cough, a sneeze, or by hiccups. Hiccups happen when your diaphragm contracts suddenly and air rushes into your lungs. Your vocal cords, membranes lying across your trachea that you use to talk, close, making a loud squeak. Coughs and sneezes clear out dust and other particles that get trapped in your airways and the lining of your nose. Colds cause coughs and sneezes for a few days, smoking can give people cough for years because some of the smoke gets stuck in the lungs.
Drops of moisture, dust and germs shoot into the air when you sneezes.
Saturday, November 24, 2007
Why do you get out of breath?
The amount of oxygen you need depends on how hard your body is working. If you are resting, you need only a small amount. If you are running or playing badminton, you use up oxygen more quickly producing enough energy. An area in your brain automatically adjusts your breathing rate to make sure you get the oxygen you need, by breathing faster and more deeply.
Gasping for air
At rest, a 10-years-old takes in about 0.25 litre (15 cu in) of air with each breath. If you take deep breaths, you will take in seven times more air than this. If you work hard, you will force more air out of your lungs and take in ten time more air.
The amount of oxygen you need depends on how hard your body is working. If you are resting, you need only a small amount. If you are running or playing badminton, you use up oxygen more quickly producing enough energy. An area in your brain automatically adjusts your breathing rate to make sure you get the oxygen you need, by breathing faster and more deeply.
Gasping for air
At rest, a 10-years-old takes in about 0.25 litre (15 cu in) of air with each breath. If you take deep breaths, you will take in seven times more air than this. If you work hard, you will force more air out of your lungs and take in ten time more air.
Breathing in and breathing out
Lungs do not have any muscles, so they cannot move air on their own. Instead, muscles in the chest make the lungsexpand, or blow up like a balloon, as air is sucked in. Most of the work of breathing is done by muscles that raise the ribs, but if you breath out hard, for example when blowing a trumpet, you use muscles on the front of your belly as well. This pushes your insides upwards, squeezing the air out of your lungs more forcefully.
Big breathers
People take, on average, more than half a billion breaths during a lifetime. Each person's lungs move about 250 000 m3 (8 million cu ft) of air, a quantity that would fill the biggest airship ever built.
Lungs do not have any muscles, so they cannot move air on their own. Instead, muscles in the chest make the lungsexpand, or blow up like a balloon, as air is sucked in. Most of the work of breathing is done by muscles that raise the ribs, but if you breath out hard, for example when blowing a trumpet, you use muscles on the front of your belly as well. This pushes your insides upwards, squeezing the air out of your lungs more forcefully.
Big breathers
People take, on average, more than half a billion breaths during a lifetime. Each person's lungs move about 250 000 m3 (8 million cu ft) of air, a quantity that would fill the biggest airship ever built.
Friday, November 23, 2007
How do lungs work?
When you breath in, air flows through the bronchi and bronchioles in your lungs, and comes to a halt in millions of air pockets, known as alveoli. These pockets are surrounded by blood vessels that are so tiny they can be seen only under a microscope. The blood vessels are so thin that gases can pass straight through them. As blood flows around the air pockets, oxygen passes into the blood, while carbon dioxide waste in the blood passes into the pockets to be breathed out.
Inside a lung
The trachea branches off to the right and left lung. Each lung is made up of a mass of subdividing airways.
When you breath in, air flows through the bronchi and bronchioles in your lungs, and comes to a halt in millions of air pockets, known as alveoli. These pockets are surrounded by blood vessels that are so tiny they can be seen only under a microscope. The blood vessels are so thin that gases can pass straight through them. As blood flows around the air pockets, oxygen passes into the blood, while carbon dioxide waste in the blood passes into the pockets to be breathed out.
Inside a lung
The trachea branches off to the right and left lung. Each lung is made up of a mass of subdividing airways.
LUNGS AND BREATHING
Human need oxygen to survive. Each time you take a breath, air rushes into your lungs and oxygen passes from the air into your blood. To get enough oxygen into your body your lungs need a very large surface area in contact with the air. If your lungs could be unpacked and laid out flat, they could wrap up your body at least 25 times.
What do lungs look like?
Lungs are like air-filled sponges. Air flows into the lungs through a tube called the windpipe. This tube divides into many smaller tubes called bronchi, and these subdivide again into even smaller tubes called bronchioles. Each bronchiole ends in a cluster of tiny air pockets called alveoli, which are buried deep inside the lungs. You can also find the diagram of lungs at www.mydr.com.au
What do lungs look like?
Lungs are like air-filled sponges. Air flows into the lungs through a tube called the windpipe. This tube divides into many smaller tubes called bronchi, and these subdivide again into even smaller tubes called bronchioles. Each bronchiole ends in a cluster of tiny air pockets called alveoli, which are buried deep inside the lungs. You can also find the diagram of lungs at www.mydr.com.au
Thursday, November 22, 2007
How does the heart work?
Your heart is made of muscle, and has two chambers, called the atrium and the ventricle, on each side. About 100 000 times a day, the heart fills with blood and then contracts to pump the blood out again. This contraction is called a heartbeat. Deoxygenated blood from your body flows into the right side of your body flows into the right side of your heart, and is pumped to the lungs, where it takes in oxygen. The oxygenated blood returns to the left side, which pumps the blood returns to the left side, which pumps the blood out through a large artery called the aorta and around your body. Each side of your heart has two valve. These are flaps that stop blood flowing backwards after each beat.
Your heart is made of muscle, and has two chambers, called the atrium and the ventricle, on each side. About 100 000 times a day, the heart fills with blood and then contracts to pump the blood out again. This contraction is called a heartbeat. Deoxygenated blood from your body flows into the right side of your body flows into the right side of your heart, and is pumped to the lungs, where it takes in oxygen. The oxygenated blood returns to the left side, which pumps the blood returns to the left side, which pumps the blood out through a large artery called the aorta and around your body. Each side of your heart has two valve. These are flaps that stop blood flowing backwards after each beat.
Why do scabs form?
If blood was like water, it would drain away through cuts and grazes. Instead, small leaks are quickly plugged, bringing bleeding to a halt. This happens because blood contains chemical called fibrinogen. When a blood vessel is cut, the fibrinogen turn into another chemical, called fibrin, which creates a maze of sticky strands. Blood cells get trapped in the strands, making a solid plug called a clot. Once a clot has formed, the skin underneath starts to heal. Eventually, the clot dries out to form a scab, which later falls off. By this time, the injury has been fully repaired.
If blood was like water, it would drain away through cuts and grazes. Instead, small leaks are quickly plugged, bringing bleeding to a halt. This happens because blood contains chemical called fibrinogen. When a blood vessel is cut, the fibrinogen turn into another chemical, called fibrin, which creates a maze of sticky strands. Blood cells get trapped in the strands, making a solid plug called a clot. Once a clot has formed, the skin underneath starts to heal. Eventually, the clot dries out to form a scab, which later falls off. By this time, the injury has been fully repaired.
Wednesday, November 21, 2007
Why is blood red?
Blood gets its colour from a red chemical called haemoglobin, which is stored in red blood cells. When blood flows through the lung, the haemoglobin collects oxygen and carries it to other parts of the body. Haemoglobin that is carrying oxygen is bright red, but it has released its oxygen into the body's cells as it flows past them, it becomes much darker. As a result, the blood flowing in your arteries is brighter red than the blood flowing in your veins.
Blood gets its colour from a red chemical called haemoglobin, which is stored in red blood cells. When blood flows through the lung, the haemoglobin collects oxygen and carries it to other parts of the body. Haemoglobin that is carrying oxygen is bright red, but it has released its oxygen into the body's cells as it flows past them, it becomes much darker. As a result, the blood flowing in your arteries is brighter red than the blood flowing in your veins.
Where does blood go?
Bloods travels around your body in a network of pipes called blood vessels. The blood vessels that carry blood away from the heart are called arteries, the one that carry it back again are called veins. Arteries and veins are connected to each other by more than 80 000 km (50 000 miles) of capillaries, tiny vessels much thinner than a hair. Arteries expand every time your heart beats. In places such as the wrist, this creates a 'pulse' you can feel.
replacement service
A single drop of blood contains about 250 million red cells and over 300 000 white cells. Red cells wear out quickly, and every day the blood makes about 2.5 billion new ones to replace them.
Bloods travels around your body in a network of pipes called blood vessels. The blood vessels that carry blood away from the heart are called arteries, the one that carry it back again are called veins. Arteries and veins are connected to each other by more than 80 000 km (50 000 miles) of capillaries, tiny vessels much thinner than a hair. Arteries expand every time your heart beats. In places such as the wrist, this creates a 'pulse' you can feel.
replacement service
A single drop of blood contains about 250 million red cells and over 300 000 white cells. Red cells wear out quickly, and every day the blood makes about 2.5 billion new ones to replace them.
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