Nervous system : The system consisting of the brain, spinal cord and the nerves. Memory : Ability to remember things. Brain : An organ inside the head that controls all our activities. Cerebrum : The largest part of the brain. Cerebellum : The lower part of the brain. Reflex action : An automatic response of the body to an event. Spinal cord : A thick cord of nerve tissues extending down from the brain.
Remember the Points
⯁ The nervous system is the most important organ system of our body. ⯁ The brain, spinal cord and nerves are the organs of the nervous system. ⯁ The brain has three parts-cerebrum, cerebellum and medulla. ⯁ The nerves are of three types-sensory nerves, motor nerves and mixed nerves. ⯁ Reflex action is an automatic response of the body. ⯁ Eyes, ears, nose, skin and tongue are our sense organs. ⯁ Our sense organs are very important parts of our body. ⯁ We should take proper care of our sense organs. Keep Note :
Human brain: The brain is our most complex organ and the centre of operations for the whole body, Controlling our thinking, memory, feelings, intelligence and actions. Approx weight of the brain: 1.2 kg to 1.5 kg. 20% of our total body energy is used by the brain. Our brain needs a constant supply of oxygen and glucose.
Cerebrum : It is the largest part of the brain and divided into the right hemisphere and left hemisphere. These two hemispheres are linked together through a thick bundle of nerve fibres Called corpus callosum.
Right hemispheres controls- spatial skill Imagination Music sense Creativity sense of art hand eye coordination.
Functions of Cerebellum and Medulla
Functions of Cerebellum
Functions of Medulla
The cerebellum is responsible for coordinating voluntary movement, balance and Posture of the body. It helps us to move smoothly and maintain the Stability in our daily activity.
It connects the brain to the spinal cord. Medulla controls involuntary actions like-heart beats. swallowing Sneezing and breathing.
Spinal cord : The spinal cord is a thick cord of nerve and tissues. It originates from the medulla and extends to the lower end of the backbone.
What are nerves?
A group of nerve cells is organized to form a nerve. There is a network of nerves throughout our body. Nerves are of three types
i) Sensory nerves - The nerves that carry messages from the sense organs to the brain or spinal cord are called sensory nerves. ii) Motor nerves - The nerves that carry messages from the central nervous system to the muscles and glands are called motor nerves. iii) Mixed nerves - The nerves that carry messages to the central nervous system as well as carry orders from the central nervous system are called mixed nerves. Reflex : A reflex action is an involuntary, automatic and sudden response of the body to an event. There are very quick responses controlled by the spinal cord. Reflexare: Reflexare is a neural pathway that controls the reflexes.
Answer the following questions
What are the major functions of the nervous system?
The Nervous system is the most important organ system in our body. It consists of the brain, spinal cord and the nerves. It is the most complex organ system of our body. The Nervous System controls all the other organ systems and hence all our activities.
Name the various parts of the nervous system.
The nervous system has two main parts:
Central Nervous System (CNS): Brain: The control center that takes, processes and sends signals. Spinal Cord: A bundle of nerves that carries messages between brain and body. Peripheral Nervous System (PNS): Nerves: Spread throughout the whole body to connect all organs. Reflex Actions: Quick, automatic responses of our body. Sense Organs: Eyes, ears, nose, tongue, and skin.. Skin: Contains nerve endings that help us feel touch, pain, and temperature.
Write the functions of each of the following:
(i) Brain: The brain is an important organ of our nervous system. Messages from different parts of the body are received by it, after processing them it sends instructions to different parts of our body. Our brain works just like a computer; it helps us to store information in our memory.
(ii) Spinal cord : The spinal cord is a thick cord of nerve tissues. It transfers information between the brain and the rest of the body. It also controls the reflex actions.
(iii) Nerves : When the brain sends any instruction, the network of nerves carry them to various parts of our body. Nerves are made up of Nerve cells called neurons.
What do you mean by reflex action?
A reflex action is an automatic response of the body to an event. Reflex actions are controlled by the spinal cord.
Name the various sense organs.
There are five sense organs in our body. They are eyes, nose, skin and tongue.
Differentiate between motor nerves and sensory nerves.
Motor Nerves
Sensory Nerves
Motor Nerves carry signals from the brain and spinal cord to muscles.
Sensory Nerves carry signals from the sense organs and skin to the brain and spinal cord.
Motor Nerves control voluntary movements, like walking or writing, and involuntary movements, like your heart beating.
Sensory Nerves help us feel sensations like touch, pain, temperature, and provide information
How would you take care of your sense organs?
We should take proper care of our sense organs as follow-
We should wash our eyes regularly with clean water. We should protect our eyes from dust particles. We should not allow water to enter our ears. We should keep our nostrils clean. We should not clean our ears with hairpins or toothpicks. We should not put our fingers, pencils or matchsticks into our nostril. We should not read in dim or very bright light We should clean every sense organ properly while taking a bath.
Fill in the blanks
1. The nervous system is a very important organ system. 2. Our body consists of an inter-connected network of nerves. 3. Cerebrum is the largest part of the brain. 4. The spinal cord is a cord of nerve tissues. 5. The medulla controls activities like breathing , heartbeat and sneezing. 6. Motor nerves carry messages from the brain to the muscles and glands.
True and False statements
1. Cerebrum is located below the cerebellum. [F] 2. Reflex action is not an automatic response of the body. [F] 3. The sense organs connect us to our surroundings. [T] 4. We should read in proper light. [T] 5. We should not clean our sense organs. [F] 6. The taste buds do not have nerve endings. [F]
