Nervous System

The central nervous system consists of the brain, the spinal cord, and the body's nerve network. This complex system is based on one kind of cells -the neurons. The brain, the mass of tissue inside the head, has the greatest number of these cells, most of which are in its outer part, the cerebrum.

Interesting Facts about Structure and Physiology of the Nervous System:

• A newborn baby's brain grows almost 3 times during the course of its first year.

• The left side of the human brain controls the right side of the body and the right side of the brain controls the left side of the body.

• A newborn baby loses about half of his nerve cells before he is born.

• As we get older, the brain loses almost one gram per year.

• There are about 13, 500,00 neurons in the human spinal cord.

• The total surface area of the human brain is about 25, 000 square cm.

• The base of the spinal cord has a cluster of nerves, which are most sensitive.

• An average adult male brain weighs about 1375 grams.

• An average adult female brain is about 1275 grams.

• Only four percent of the brain's cells work while the remaining cells are kept in reserve.

• The brain utilizes 20 % of our body's energy i.e., it uses 20% of one's blood and oxygen and makes up only 2 % of our body weight.

• The human brain stops growing by 18 years of age.

• The human brain is very soft like butter.

• Sixty percent of the human body's nerves end in the forehead and the hands.

• The brain continues to send out electric wave signals until approximately 37 hours after death.

It is estimated that there are over 1, 000,000,000,000,000 connections in the human brain.

• Human brain constitutes 60 % of white matter and 40 % of grey matter.

• The average length of the human brain is about 167 mm and its average height is 93 mm.

• On an average, 100, 000 to 1000, 000 chemical reactions take place in our brain.

• The Nervous system transmits messages to the brain at the speed of 180 miles per hour.

• Reading aloud to children helps to stimulate brain development.

• The right side of the human brain is responsible for self-recognition.

• Men listen with the left side of the brain and women use both sides of the brain.

• The human brain is made up of a staggering 15 billion cells with about thousand billion connections between these cells. However, it weighs less than 3 pounds.

Senses

Our senses are the physical means by which all living things see, hear, smell, taste, and touch. Each sense collects information about the world and detects changes within the body. Both people and animals get all of their knowledge from their senses, and that is why our senses are so important. All senses depend on the working nervous system. Our sense organs start to work when something stimulates special nerve cells called receptors in a sense organ. We have five main sense organs. They are the eyes, ears, nose, tongue, and skin:

Seeing

• The part of your eye that gives it its colour is called the iris. It has lots of tiny muscles that open your pupil (the round hole in the centre) to let in more light when it's dark. The larger the pupil, the more light can enter.

• The retina has millions of two main nerve cells to catch light. Rods, which are mostly around the sides, are best at helping you to discriminate light and dark. Cones, which are near the centre, are for detecting colour. Nerve cells from the retina connect your eye to the parts of the brain that process vision, the occipital lobes, which are located in the back of your head.

• Like your fingerprints, irises and retinas are individual.

Hearing

• The three smallest bones in the body - named the hammer, the anvil and the stirrup (the smallest, at about 3 millimetres) pass sound from your eardrum to your inner ear.

• The inner ear has special nerve cells to pass sound information for processing by the brain, but a part of the inner ear helps you to keep your balance.

Smelling

• There are about 10 million smell receptors up in the space behind your nose for detecting smells. Working together with you brain, this group of nerve cells is able to detect about 10,000 different odours.

• Children can distinguish between the smell of their siblings and other children of the same age.

• Babies recognise their own mothers' smell and mothers recognise their own babies' smell.

Taste

• You are born with about 10,000 taste buds, but this drops over time to about 5000 by the time you are old.

• Taste buds detect sweet, sour, salty and bitter. Tasting is about 80% smell, and your sense of smell increases when you are hungry.

Touch

• The skin is the largest organ in the body, weighing at about 6 - 10 lb. Your skin detects touch via receptors for pain, pressure and movement, cold and heat.

• Most touch receptors are for pain. Skin is least sensitive in the middle of your back, and most sensitive in hands, fingertips, and lips.