Chapter: 8 Human Body: Nervous System and Sense Organ

Sub: Science Lesson Note Grade: V

Chapter: 8 Human Body: Nervous System and Sense Organ

CONCEPT MAP

Vocabulary : Neuron, Spinal cord, Reflex action, Reflex arc, Cornea, Pupil,

Retina, Iris, Pinna, Eardrum, Stimulus.

The Nervous

system and

sense organs

Nervous System Sense Organs

Brain Nerves Spinal

cord

Reflex

Action Eyes

Ears

Nose

Skin

Tongue



The system used to send, receive and process messages to and from

the various organs and organ systems inside the body is called as

Nervous System.

It consists of:-

Brain

Spinal cord

Nerves

Brain

Functions of brain:-

It is the main control centre of the body.

Brain monitors and regulates the body’s action and reactions.

It continuously receives information, rapidly analyzes this data

and then responds.

It also controls bodily actions and functions.



Parts of Brain:-

1. Cerebrum

It collects information from all sense organs and controls

thinking and reasoning.

Centre of thinking, learning and memory.

2. Cerebellum

It helps in coordinating body movements.

Also responsible for the body balance and posture.

Centre responsible for creativity.

3. Brainstem

It lies below the cerebellum.

Connects brain to the spinal cord

It controls breathing and heart rate.



Nerves

Nervous system consists of billions of nerve cells called neurons.

Nerves acts as carriers of signals to and from the brain to all parts of the

body.

There are three main types of nerves:-

Sensory nerves- They carry messages from different parts of

body to the brain or the spinal cord.

Motor nerves- they carry messages from the brain or spinal cord

to different parts of the body.

Mixed Nerves- works as both ways like sensory and motor

nerves.



Spinal cord

Spinal cord is a long, thin, tube-like

structure.

It extends from the brain down the

spinal column.

Acts as bridge between the brain and

the rest of the body to transmits signals

to and from the brain.

Plays a major role in our reflex actions.



Time please

A. Match the columns.

Heart-Four chambers

Blood-Red coloured fluid

Cerebellum-Balance

Blood vessels-Pipelines

Cerebrum-Thinking

B. Give one word for the following:-

1. A medium that carries vital gases within the human body:

Blood

2. A muscular organ that helps to pump blood to all parts of the

body: Heart

3. The thickest blood vessels: Artery

4. The part of brain that controls the heart rate: Brainstem

5. The main control centre of the body: Brain



Reflex Action

A reflex action is an immediate and rapid response to a stimulus.

Reflex actions are not directly controlled by the brain.

In humans, reflexes occur through a pathway called the

reflex arc.

A reflex action occurs very quickly.

Signals are directly sent from spinal cord without involving

the brain.



The reflex arc works as follows:-

The sensory neuron carries the message from the point of

stimulus to the spinal cord.

The spinal cord receives the message, processes it and gives the

response.

The motor neuron then carries the message to the point where

the reflex occurs.

Spinal cord sends reflex messages in less than a second.



Sense organs our body has five sense organs.

1. Eyes:-

We see with our eyes.

Eyes are located in the eye sockets of the skull.

Eyelids and eyelashes protect the eyes from dust.

Structure of the eye:-

Cornea- A thin, transparent layer covering the front part of the

eye is called cornea.

Iris- The round, coloured part of the eye, located behind the

cornea, is called iris.



Pupil- The opening at the centre of the iris is called the pupil. Light

enters through the pupil.

Lens- A lens located just behind the pupil helps to focus the light.

Retina- Light passes through the lens and falls on a lining, called

the retina, which is sensitive to light. The retina sends messages to optic nerve, which carries the

message to the brain.



2. Ears :-

We hear with our ears.

We have a pair of ears

Structure of the ear:-

There are three main parts of ear- outer, middle and inner ear.

Outer ear- The part of ear that can be seen from outside is called

outer ear or pinna. Outer ear receives sound.

Middle ear- It consists eardrum, the sound travels to the middle

ear and hits the eardrum.

Eardrum-

It is a thin, membrane like structure.

It vibrates like a stretched rubber band when you release

it.

Inner ear- the vibrations are then passed on to the inner ear.

Inner ear transforms the sound into a nerve signal, which is sent

to the brain via nerves.

3. Nose :-

We smell with our nose.

It helps to detect different odours.

It helps us in breathing.

Structure of nose:-

It has two nostrils that are lined with hair and mucus to trap dirt

from the air.

Nasal cavity that is lined with cells that are sensitive to smell.

These cells detect smell and send the messages to brain though

nerves.



4. Skin :-

It helps us to feel, touch and sense heat, cold, pressure and

pain.

It forms a continuous, covering layer around our entire

body

There are several nerves under the surface of skin.

These nerves detect touch and send messages to brain.

5. Tongue :-

It helps us to sense different tastes like sweet, sour, bitter

and salty.

There are several taste buds located over the entire surface

of tongue

These taste buds detect taste and send messages to the

brain through the nerves.



Let’s Practise

A. Fill in the blanks with the correct words:-

1. Brain controls all the organs of the body.

2. The spinal cord is involved in the reflexes of the body.

3. The spinal cord acts as a bridge between the brain and the rest

of the body.

4. Reflex actions are not directly controlled by the brain.

5. The outer or external ear is called the pinna.

B. Tick the correct option.

1. Which of these is not a part of the nervous system?

a. Brain b. nerves c. Spine d. Spinal cord

2. The nervous system consists of billions of nerve cells, called

a. Neurons b. vessels c. veins d. arteries

3. It is responsible for body balance.

a. Cerebellum b. Cerebrum c. Spinal cord d. Brainstem

4. The long, thin, tube-like structure that extends from the brain

down the spinal column is called the ----------------.

a. Relex arc b. Cerebellum c. spinal cord d. neuron

5. Which of these is not a sense organ?

a. Tongue b. Skin c. Nose d. Hair



C. Short answer questions

1. List the main organs of the nervous system?

Ans1. The Brain, spinal cord, and the nerves make up the nervous

system.

2. State two functions of the cerebellum.

Ans2. The cerebellum is responsible for controlling body balance and

posture.

3. Where is the spinal cord located?

Ans3. The spinal cord acts as a bridge between the brain and the rest

of the body and it extends from the brain down the spinal column.

4. What is reflex arc?

Ans4. In human beings, reflexes occur through a pathway called the

reflex arc.

5. List the three types of nerve found in our body.

Ans5. Three types of nerves are sensory, motor and mixed.



6. What is retina? State its functions.

Ans6. Retina is a light-sensitive lining behind the lens, at the back of

our eye. It sends messages to the optic nerve, which carries the

message to the brain.

D. Long answer questions

1. What is brain? Draw a labelled diagram of the human brain and

state the functions of the major parts.

Ans1. Brain is the main control centre of the body, protected by the

skull. The brain monitors and regulates the body’s actions and

reactions. It continuously receives information, rapidly analyzes this

data and then responds. It also controls bodily actions and functions.

For diagram—refer page no.79/ lesson notes.

Functions of the major parts of brain:-

Cerebrum- It collects information from all sense organs and controls

thinking and reasoning. It is the centre of thinking, learning and

memory.



Cerebellum- It helps in coordinating body movements. It is also

responsible for the body balance and posture and is the centre

responsible for creativity.

Brainstem- It lies below the cerebellum. It connects brain to the spinal

cord and It controls breathing and heart rate.

2. List the three types of nerves and mention their functions.

Ans 2. The three main types of nerves are-

Sensory nerves- They carry messages from different parts of

body to the brain or the spinal cord.

Motor nerves- they carry messages from the brain or spinal cord

to different parts of the body.

Mixed Nerves- they carries messages from different parts of the

body to the brain or spinal cord, as well as from the brain or

spinal cord to different parts of the body.

3. With the help of labelled diagram, explain the reflex arc.

Ans3. In humans, reflexes occur through a pathway called the

reflex arc. ( for diagram refer figure on page no.81 of textbook)



A reflex action occurs very quickly because signals are directly

sent from spinal cord without involving the brain.

The reflex arc works as follows:-

The sensory neuron carries the message from the point of

stimulus to the spinal cord.

The spinal cord receives the message, processes it and gives the

response.

The motor neuron then carries the message to the point where

the reflex occurs.

Spinal cord sends reflex messages in less than a second.



4. Draw a labelled diagram of the structure of the ear and state

the function of cochlea.

Ans4. Please refer the given fig. in lesson notes and page no. 83

of coursebook

Function of cochlea (inner ear):-

The outer ear receives sound. This sound travels to the middle

ear and hits the eardrum. The eardrum is a thin, membrane like

structure. It vibrates like a stretched rubber band when you

release it. The vibrations are then passed on to the inner ear

(cochlea). The inner ear transforms the sound into a nerve

signal, which is sent to the brain via nerves.

Chapter: 8 Human Body: Nervous System and Sense Organ

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