Science - Chapter 1 Form 2

8/2/2019 Science - Chapter 1 Form 2

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Done By :

Chan Jia Wei

Steve Koh

Chin Yein Yee


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Our senses detect stimuli and we respond.

Human have receptors or sense organs such as:

The skin responds to touch , pressure, pain,

heat and cold.

The tongue responds to chemical in ourfood and drink. It gives us our sense of

taste .

The nose responds to chemical in the air. It

gives us our sense of smell.

The ears respond to sound vibrations and

movements. They give us our sense of

hearing and our balance. The eyes respond to light rays. They give us our sense of

sight.

Nervous pathway from stimulus to response:

Stimulus Sensory organs Sensory nerves Brain

Response Motor nerves

Humans have 5 senses: touch, taste, smell, sight,

and hearing. The senses are based on receptor cells

or groups of receptor cells called sense organs.

Receptors respond to stimuli and send nerve

impulses along sensory neurons. The braininterprets the nerve impulse and, thus, we perceive

the impulse as one of our senses.


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SkinThe skin is made up of three layers- theepidermis, the derm is and the fatty layer.

There are many different types of sensors in the skin.

The number of sensors varies in different parts of our body.

The sensitivity of the skin depends on two factors: The thickness of the epidermis

The number of receptors

- Pain receptors are at the skin

surface. They are branched and

respond to intense stimuli.

-Some touch receptors are attachedto the base of our hair. So you can

feel it they are being pulled.

-Pressure receptors are in the fatty

layer. It is used to detect pressure

exerted on the skin.

-Heat receptors are located belowthe epidermis. It detects heat or any

rise of temperature.

-Cold receptors are also located

below the epidermis. It detects a

cold substances or any fall in

temperature


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TongueYour senses of taste and smell are closely linked. They are both

chemical senses.

What things can you taste?

-You can only taste sweet, sour, bitter, and salty things. Peoplethink that they can taste

other things but they are actually using their sense of smell.

The sensors that give you your sense of taste are found in little

grooves on your tongue.

They are call taste buds.

Each taste bud can only taste one taste.The different types of taste buds are found in particular areas on

the tongue.

The taste buds send nervous impulses along the nerves to the

brain for its interpretation.

When food is placed in the mouth, the saliva dissolves the food

and the chemicalsstimulate the taste buds.

Nervous pathway for detecting taste:

Food(stimuli) Saliva dissolves food Chemical in food stimulate

taste buds

Taste buds send impulses to brain . The brain interprets the

impulses

Different areas of the

tongue are especially

sensitive to different

taste


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NoseOur nose also senses

chemical but it is

thousands of time more

sensitive than your

sense

of taste.

Smells are chemical in

the air.

The chemical dissolve in

the moist lining of your

nose.

They stimulate sensors

in your nose to send

impulses to the brain.

The brain interprets

these impulses as

different smells.

The nasal cavities have

glands which produce a

sticky fluid called

mucus.

A person having a cold cannot

smell well. This is because the

sensory cells are covered

with a lot mucus and not much

chemicals can reach and stimulate

the sensory cells.

The nervous pathway can be

summarized as follows:Chemical enter the nose

Chemical dissolves in mucus

Chemical stimulate the

sensory cells The sensory cells

produce nervous impulses

Nervous impulses aresent along the nerves to the brain

The brain interprets the impulses

as a certain smell


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EarsThe air around us is full of sound waves.

You ears work by converting these sound waves into nerve

impulses.

This I show it happens:

The outer part of your ear funnels the sound

waves into the ear canal

The sound waves travel along the ear canal

to the eardrum.

The ear drum starts to vibrate when sound

waves hit it

The vibrations are passed on to 3 little bones called the

ossicles

The ossicles pass the vibrations on to the inner eardrum or

oval window When oval window vibrates it causes fluid in the cochlea to

move

Inside the cochlea are lots of tiny, sensory hairs. Movement of

the fluid sets

these hairs vibrating. They send off nerve impulses to the brain

The brain interprets these impulses as sounds


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Ear Structur


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EyeThe nervous pathway is as follow:

Cornea aqueous humour pupil eye lens vitreous humour retina

brain optic nerve

Light travels in a straight line.

Light can travel through vacuum

Light can be reflected and absorbed

A periscope and a kaleidoscope uses the reflection of light

Light can be refracted.

Light is refracted when light travels from a medium to another medium.

Defects of Vision

Long-sightedness

Short-sightedness

Astigmatism

Colour blindness Optical illusion

Blind spot

There are two kinds of vision:

Stereoscopic vision

Monocular vision

Science - Chapter 1 Form 2

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