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

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

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

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

Tag :fingerprints

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.

Tag :skin ridges
Tag :fingernails