THE WORLD THROUGH OUR SENSES

Receptor

Our body have different types of receptors. These are:

• pain receptor• touch receptor• heat receptor• cold receptor• pressure receptor

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Human skin

Try to answer

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The degree of sensitivity of the skin depends on the:

1.Thickness of the epidermis• The thinner the epidermis, the more sensitive

the skin is to the stimulus2. Number of receptors present PMR 05

• The more receptors found on the skin the more sensitive is that part of the skin.

Other functions of the human skin.

• Water proof• prevent water loss from skin.

• Prevents entry of microorganisms that cause illnesses.• Remove waste products

• excess water, urea and mineral salts.• Produces Vitamin D in the presence of the sunlight.• Stabilise body temperature

Fill in the blank with the suitable terms given in the box.

Receptors thickness thinner sense of touch touch more number

• The skin is an organ of __________________ • There are five types of __ ___ in the skin sensitive to various

stimuli.• The sensitivity of the skin depends on the ___________ of the

epidermis and the ____________ receptors on the skin.• The ____________ the epidermis, the more sensitive it is to

stimulus.• The ________ receptors there are on the skin, the more sensitive it

is to stimulus.• Blind people use their ____ to help them read Braille

Human Tongue

Try these

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PMR 2012

Human nose

Try to answer ….

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Sense of smell• When we have a cold or

flu, a lot of mucus is produce. The smell receptors are surrounded by this thick layer of mucus and vary little of chemical vapor gets to the smell receptors. Therefore, the smell receptors do not get stimulated enough to effectively function as a sensory organ of smell.

The sensitivity of the nose towards stimuli is influenced by the following factors: PMR 05

• The strength of the smell. A stronger smell will be detected by the nose easily compared with a weaker smell.

• The presence of mucus in the nose. A lot of mucus will reduce the sensitivity of the nose.

Human ear

• A human ear has three main part.1. the outer ear, filled with air.2. The middle ear, filled with air.3. The inner ear, filled with liquid

Human ear

Try to answer

Test

FUNCTIONS OF DIFFERENT PARTS OF THE HUMAN EAR

Part functionOUTER EARPinna collects and directs sound waves into the ear canal.

ear canal / auditory canal transmits sound waves to the eardrum.

Eardrum vibrates and transmits sound waves to the ossicles.

MIDDLE EAROssicles

intensify the vibrations of the sound waves by 22 times before transmitting to the oval window.

Eustachian tube balances the air pressure at both side of the eardrum.

oval window transmits sound vibrations from the middle ear to the inner ear.

INNER EARCochlea transforms sound vibrations into impulses.

semicircular canals balance the body position.

auditory nerves send messages to the brain which interprets the messages as sound.

Stereophonic hearing

• Stereophonic hearing is hearing using both ears.• The advantages of stereophonic hearing:

– enables the direction of the source of hearing to be detected more accurately.

– This is because the ear nearer the source of sound receives sound louder and earlier than the other ear.

– Animals that have stereophonic sound can detect the presence of preys and predators more quickly.

Properties of sound

– sound can transferred through;– solids– liquids– gases– cannot be transferred through in vacuum.

(particles in solids and liquids are closer each other compared to the molecules in gases. Vacuum is space that does not have any particles.)

ANIMAL Frekuansi snake 100-800Hzfrog 50-10 000Hzdog 10-50 000Hzcat 60-60 000Hzbat 1000-120 000Hz

grasshopper 100-15 000Hzwhale 10-50HzHuman 20hz – 20 000 hz

The range of frequencies of hearing in man is 20 Hz until 20 000 Hz. The following table shows the range of frequencies of hearing of several animals:

Different people have different limitations of hearing.

Experiment PKBS 1 2012 F2

Reflection and absorption of sound• Sound can be reflected or absorbed by the surface of an

object.• The sound reflected repeatedly from one surface is known

as echo.• Surfaces that are smooth, even and hard are good sound

reflectors and produce loud echo. For examples, concrete, plank, metal and mirror

• Surfaces that are rough, hollow and soft are good sound absorbers and produce weak echo. For examples cloth, sponge, cork, rubber, carpet and cushion.

To overcome the limitations of hearing, we use

i. the stethoscopeenables doctor to detect the soft heartbeats of patients.

ii. hearing aidscollects sound signals before being sent to the middle ear.

iii. amplifierboosts weak sound signals.

Human eye

choroid

Human eye

Human eye

Human eye

FUNCTIONS OF DIFFERENT PARTS OF THE HUMAN EYE

Part Structure /

characteristic

Function

Sclera Maintains the shape of the eyeball Protects the eyeball

cornea rybb

ChoroidsConjunctivairispupil

Lens PMR 04Transparent and elastic convex lens

Refracts and focuses light onto the retina.

ciliary musclesupportive ligamentvitreous humouraqueous humourRetina PMR 2011optic nerve

Human eye

Yellow spot

Daily activities

pupil

iris

dark roombright room

Daily activities

Stereoscopic vision • - using both eyes.• predator• Advantages

– See three-dimensional pictures of objects.

– Enables more accurate estimation of distance and position.

• Disadvantages• A narrow vision field.

Monocular vision.• using only one eye.• prey• Advantages• having a wide vision

field.

• Disadvantages• cannot estimate

distance accurately.

Experiment Textbook pages 20

Mechanism of Sight PMR 03, 07• The eye lens focuses the image onto the

retina by changing the thickness of the eye lens. The thickness of the lens is changed by the cilliarry muscles.i.Focusing near objectsTo focus near objects onto the retina, the cilliarry muscles contract. The eye lens become thicker.

ii. focusing distant object.To focus distant objects onto the retina, the cilliarry muscles relax. The eye lens becomes thinner.

Reflection of light

Rough surface Flat, shiny, smooth

Contoh, BOMBA, POLIS

BOMBA

Device used concept reflection

Kalaideskop – tak guna concept reflection

Reflection of light

Refraction of light

Refraction of light

Refraction of light

Smooth, shiny, flat

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GH

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Less dense

denser

Short sightedness

Causes:1. Eye ball is too big2. Eye lens is to thick.

Correction:

Wearing concave lens

Long sightedness

Causes:1. Eye ball is too small2. Eye lens is to thin.

Correction:

Wearing convex lens

Comparison between SS and LS

Astigmatism • Light is

refracted to multiple areas of the retina.

• This defect can be overcome by wearing glasses with cylindrical lenses or contact lens or by surgery.

Astigmatism

Instructions

1) First, I want you to form groups of four. In your group, discuss why some people wear glasses

2) Next, I want you to look at the first picture on the screen

3) Click and drag the picture from left to right. Observe what happens to the image

4) Then, repeat the activity on the second and third pictures

Experiment short sightedness & long sightedness

Questions

1) Why do some people wear glasses?

2) What is the cause of short sightedness?

3) Where does the image fall when a short sighted person look at a far object?

4) What kind of lens is used to correct short sightedness?

Types of Defects Able to see close/near objects(clear/blur)

Able to see distant object (clear/blur)

Types of lens used to correct defects

1) Short sightedness

2) Long sightedness

3) Astigmatism

Formative Assessment

Complete the diagram

Short sightedness Long sightedness

The image falls _______ of the retina The image falls ______of the retina

Short sightedness & long sightedness

Optical illusion

Optical illusion

Blind spot

The blind spot is a spot on the retina of the eye that cannot detect light stimulus.The image of the object formed at the blind spot cannot be seen by the eye because there are no light-sensitive cells (photoreceptors) at the blind spot.

Tropism • Plant response to external stimulus• Plants grow towards stimulus called positive tropism• Plants grow away from stimulus called negative tropism

AnhydrousCalciumchloride

Phototropism

• Response to light.

Hydrotropism• Response to water

Geotropism

• Response to gravity

Thigmotropism• Response to touch• move towards – to obtain

support

Nastic movement• Response to touch• Move - run away

Penutup

2. Tasbih Kifarah.

1. Baca Surah Al-`Ashr

The end