Key Points / Definitions of Scientific Terms
- Organ System - A group of organs that work together to perform a particular function is called an organ system.
- Spinal Cord - A thick cord of nerve tissue that extends down the brain is called spinal cord.
- Reflex Action - The sudden automatic response of the body that is controlled by the spinal cord to an action
E.g. blinking of eyes, watering of mouth.
- Sense Organs - The organs that connect us to the outside world.
- Iris - The coloured part of the eye.
- Pupil - The circular opening in the iris that regulates the amount of light passing to the retina.
- Retina - The innermost layer of the eyeball.
- Cornea - The transparent outer covering of the eye which protects iris and pupil.
- Mixed Nerve - The nerve that carry message to the brain as well as bring orders from the brain.
- Brain - It is the control centre of the human body.
Questions & AnswersQ1. Name the different parts of the brain. Mention the function of each part.
Ans. The different parts of brain are cerebrum, cerebellum and medula oblongota. Functions of each part:
- Cerebrum - Controls our thoughts, voices and senses. It helps in memorizing things. It is the centre of intelligence.
- Cerebellum - Coordinates the muscular actions. It also maintains balance in our body and keeps us in upright posture.
- Medulla - Controls involuntary actions like breathing, heartbeat, blood circulations etc.
Q2. What are nerves and what are their functions?
Ans. Nerves are long thread like structures made of bundles of cells called neurons. Their function is to carry messages from the brain to other parts of the body.
Q3. How is our brain protected from injury?
Ans. The space between the skull and the brain and also inside the brain is filled with a clear fluid which serves as a cushion against jerks and injuries.
Q4. What is the difference between sensory nerves and motor nerves?
Q5. What happens when the brain does not have continuous supply of blood and oxygen?
Ans. When the brain doesn't have continuous supply of blood and oxygen then a person faints as his brain does not receive enough blood from the heart.
Q6. How can you keep your skin healthy?
Ans. We can keep our skin healthy in the following ways:-
- By using soap and water for removing dust and sweat.
- Wearing clean and comfortable clothes.
- By treating cuts or scratches on the skin with an antiseptic lotion.
Q7. How can you take care of your eyes?
Ans. We can take care of our eyes in the following ways:-
- Clean your eyes regularly with cold water.
- Do not study in dim light or in moving vehicle.
- Do not watch TV or play computer games for long period of time.
- Never rub your eyes with dirty hands or towels.
Q8. Describe the structure of an eye with a neat and labelled diagram.
Ans. Structure of an eye: -
- The front part of the eye is protected by a transparent covering called corona.
- The coloured part of the eye is called the iris.
- The black spot in the centre of the iris is called the pupil through which light enters the lens.
- The image is formed on the retina.
- Sensory nerve called the optic nerve sends message to the brain.
Tick (circle) the correct answer1. The bulb-shaped (medulla / nerve / cerebrum) connects the brain to the spinal cord.
2. The brain needs a continuous supply of blood and (oxygen / nitrogen / carbon dioxide).
3. Blinking of the eyes is an example of a (voluntary / reflex / involuntary) ___ action.
4. Our nervous system consists of the brain, spinal cord and
(a) blood vessels
Ans. (d) nerves
5. A person might fain if his does not send enough blood to his
Ans. (d) brain
6. When we happen to touch a hot object, the sensory nerve immediately passes a message to the
(c) spinal cord
Ans. (c) spinal cord
7. To clean a blocked nose, we must inhale
(d) none of these
Ans. (c) steam
Write True or Fales1. The cerebellum coordinates the actions of the muscles and makes them work together. (T)
2. The part of the brain that controls our senses is called the cerebrum. (T)
3. The motor nerves bring messages from the sense organs to the brain or spinal cord. (F)
4. The actions controlled by the spinal cord are called reflex actions. (T)
5. The pupil is the opening in our eye through which light enters the lens. (T)
6. The ears enable us to keep our balance. (T)
Complete the series1. sensory nerves : message : : motor nerves : orders.
2. memory : cerebrum : : heartbeat : medula.
3. cerebellum : muscles : : cerebrum : intellectual activities.
4. eyes : sight : : skin : touch.