Nervous system and sense organs control the entire body. It is expected that the student should be aware of the functioning of these systems in a cursory way.

For success in the entrance tests following points are important to retain.

• The nervous system controls all other systems of the body.
• The nervous system is made up of the brain, the spinal cord, and nerves.
• Nerves are like wires that link the body organs and muscles to the brain and spinal cord.
• Nerves are made up of neurons or nerve cells.
• Nerve cells have special thread-like parts called filters.
• Sensory Nerves: The nerves which are connected to the sense organs and carry the messages from sense organs to the brain or spinal cord are known as sensory nerves.
• Motor Nerves: The nerves which carry orders from the brain or the spinal cord to the muscles and glands are known as motor nerves.
• The message by the motor nerves results in the movement of the muscles or secretion by glands.
• Mixed Nerves: These nerves do both the functions i.e. they carry messages to the brain as well as carry orders from the brain.
• There are some actions which are automatic and we do not have to think before the act. These actions are called as reflex actions.
• Some of the human reflexes are coughing, sneezing, blinking and jumping when frightened and watering of mouth on seeing some tasty food.
• The brain is the main control centre of the body.
• The brain is divided into left and right halves.
• The brain attains its full size by the time a person is six years old and it weighs about 1.4 kg.
• The brain is a very delicate organ and therefore it is well protected, located inside a hard brain box or skull.
• Between the skull and the brain is present cerebrospinal fluid which absorbs the shocks, bumps and jerks.
• The brain needs plenty of food and oxygen.
• The brain uses about 1/4th of all the oxygen used by the body.
• The brain has three main parts the cerebrum, the cerebellum and the brain stem or medulla.
• The cerebrum is the largest part of the brain and makes about 90% of the brain tissues.
• The cerebrum controls speech, memory and intelligence.
• Cerebellum remains effective while running, riding a bicycle and also to keep your body balanced.
• The brain stem connects the brain to the spinal cord.
• The medulla controls many vital functions such as breathing and blood circulation.
• The eyes, ears, nose, tongue and skin are considered as the important sense organs of the human body.

Eyes

• Eyelids and eyelashes help to keep dust and dirt out of our eyes.
• The light coming from objects passes through the cornea.
• Then it goes through an opening: the pupil.
• The iris provides colour to the eyes.
• The iris controls the amount of light entering into our eyes by changing the size of the pupil.
• Image is formed on the screen of our eyes called the retina.
• The iris closes down in bright light and opens or widens in dim light.
• The optic nerves carry the messages from the eyes to the brain.

Care of the Eyes

• Wash and clean your eyes regularly with cold water.
• Do not read in dim or very bright light.
• Do not read in a moving vehicle and while lying down.
• Stay away at least six feet while watching T.V.
• Never rub your eyes with dirty hands.

Ears

• The ear is the sense organ which helps us to hear.
• The outer part of the ear helps in collecting sound.
• Our ears should be protected from the hard blow and loud sound.

Care for Ears

• Do not let water enter the ears.
• Never try to clean ears with a hairpin, toothpick or matchstick or any sharp object.
• consult a doctor in case of any ear ache.

Nose

• The nose is the sensory organ which detects odour.
• The nose has nerve cells where a chemical reaction occurs and the message is sent to the brain.

Care of Nose

• We should regularly clean our nose with water.
• We should never put a finger in our nose.
• Use nasal drops or inhale steam to clear a blocked nose.

Tongue

• The tongue is a sense organ which detects the taste of our food.
• There are four types of tastes: sweet, salty, sour and bitter.
• The tongue also has receptors for heat, cold, pain and texture.

Skin

• The skin forms a protective covering over our body.
• The five sensations that we can feel through our skin are touch, heat or cold, pressure, pain and tickling.
• Some of our waste water and salts are also removed from our body in the form of sweat.

Care for Skin

• We should always keep our skin clean.
• We should avoid wearing clothes used by others as we may get skin diseases.
• We must always wear clean clothes.
• We should take a bath to keep our skin healthy and clean.