The Nervous System
The nervous system is the most complex of all the body systems. It is also the most important system as it controls all the other body systems and the sense organs. The nervous system is made up of three parts: the brain, the spinal cord and the nerves.
Brain
The brain is the control centre of the body. Since it controls all the actions of our body, it is also called the ‘master organ of the body’.
The brain is made up of cells. On the outside, it is protected by the skull. Between the brain and the skull, there is a fluid. This fluid acts as a shock absorber and protects the brain from injuries.
The brain has three main parts: cerebrum, cerebellum and medulla.
Cerebrum:
The cerebrum is the upper part of the brain. It is dome-shaped and is the largest part of the brain. It is covered
Cerebellum:
The cerebellum is located below the cerebrum, towards the back of the brain. It is much smaller than the cerebrum. It controls the muscle movement and helps us to keep our balance. If the cerebellum is not functioning well, our body posture is affected and movement becomes jerky.
Medulla:
The medulla is a stem-shaped structure. It connects the brain to the spinal cord. The medulla controls all our involuntary activities such as breathing, heartbeat and blood circulation. The medulla works even while we are asleep. The medulla is also known as the brain stem.
The right half of the brain controls the left side of the body. Similarly, the left half of the brain controls the right side of the body. Thus, when one side of the brain is damaged, the opposite side of the body gets affected.
Spinal cord:
The spinal cord originates from the medulla and extends almost till the lower end of our backbone. It is surrounded and protected by the vertebral column. The spinal cord itself is made up of many nerves. Most nerves originate from the spinal cord and form a network all around in our body. All information between the brain and the rest of the body is transferred with the help of the spinal cord. It also controls the reflex actions, that is, those actions that do not involve the brain.
Nerves
Nerves are like a network of telephone wires. They connect every part of the body to the brain or spinal cord. Nerves are specially designed to carry messages.
There are three types of nerves: sensory nerves, motor nerves and mixed nerves.
Sensory Nerves carry messages from the sense organs to the brain or spinal cord.
Motor Nerves carry orders from the brain or spinal cord to the concerned organs such as glands and muscles for actions.
Mixed Nerves carry messages to the brain as well as bring orders from the brain to the concerned organs.
Sense Organs
We have five sense organs: eyes, ears, nose, tongue and skin. They are associated with sight, hearing, smell, taste and touch respectively.
Our sense organs have special sensory receptors, which pick up information from the surroundings. They pass on this information to the brain via nerves. Thus, the brain enables us to keep contact with our surroundings.
Let us learn how our sense organs work.
Eyes:
Eyes are one of the most important sense organs. They help us to see and identify things. Each eyeball is well fitted into a socket. It is protected by the eyelids and eyelashes. They prevent the dust and dirt from falling into our eyes. The coloured circle in the eye is iris. In front part of the eye is the transparent circular part called the cornea. The black spot in the centre of the iris is pupil. Light enters the eyes through it. The lining at the back of the eye is called retina. The picture or image of an object is formed on the retina. A sensory nerve called the optic nerve connects the eye to the brain.
Care of the eye
Wash your eyes a number of times in a day with clean water.
Do not read anything in a moving vehicle.
Do not read while lying down on the bed. Maintain a straight posture while reading.
Never read in dim light.
Clean your eyes with a clean towel.
Do not watch television or work on computers for long hours.
Get your eyes checked in every six months.
Ears:
The ears help us to hear sounds. They help us to maintain balance. They are situated in the head region. The ear is made of three parts— the outer ear though which sound enters; the middle ear and the inner ear. When sounds are made, they set up movements in the air called as sound waves. The outer ear, also called the pinna, acts like a funnel.
It collects the sound waves and sends them through the eardrum present in the middle ear. The middle ear is made up of three small bones. This system of bones sends the sound waves to the inner ear. The cochlea present in the inner ear has fluid filled spaces. Here the waves are changed into electrical signals and sent to the brain by the nerves. The brain interprets these signals as sound. The ear (inner ear) also maintains the balance of the body.
Care of the ear
Never clean your ears with a matchstick or pin.
Use a dry towel to clean your ears.
Visit a doctor if you have an earache.
Nose:
The nose helps us to smell and breathe. There are millions of nerve endings on the upper part of the nose. When the smell reaches these hair like nerves, they send message to the brain through a main nerve called the olfactory nerve. The brain identifies the smell. The tiny hair present in the nostrils prevents dust from entering inside the nose.
Care of the nose
Breathe through nose.
Keep your nostrils clean.
To clear a blocked nose, inhale steam.
Tongue:
The tongue helps us to identify different tastes. It also helps us to speak. The surface of the tongue is covered with taste buds. The nerve ending in the taste buds help us to identify different tastes such as sweet, salty, sour and bitter.
Skin:
The tongue helps us to identify different tastes. It also helps us to speak. The surface of the tongue is covered with taste buds. The nerve ending in the taste buds help us to identify different tastes such as sweet, salty, sour and bitter.
Care of the skin
Keep the skin clean using a soap and water.
Wear clean clothes.
Drink plenty of water and eat nutritious food.
Treat a skin injury with an antiseptic to prevent infection.