senses

1.1Sensory Organs

1.21.2 Sense of TouchSense of Touch

1.31.3 Sense of Smell Sense of Smell

1.41.4 Sense of Taste Sense of Taste

1.51.5 Sense of Hearing Sense of Hearing

1.61.6 Sense of Sight Sense of Sight

1.71.7 Light and SightLight and Sight

1.81.8 Sound and HearingSound and Hearing

1.91.9 Stimuli and Responses in PlantStimuli and Responses in Plant

Teacher

1.11.1 Sensory OrgansSensory Organs

Sensory Organs and Their StimuliSensory Organs and Their Stimuli

How do we know what is going on around us? How do we know what is going on around us?

Humans have five senses. Humans have five senses.

help us to detect objects and the changes in the help us to detect objects and the changes in the surroundings. Our five senses surroundings. Our five senses are the sense ofare the sense of

sight,sight, smell taste hearing

Sensory Organs and Their StimuliSensory Organs and Their Stimuli

Sensory organs

Stimuli

Found in parts of the body

Changes/ objects that

can be detected by our senses

Let’s go to the garden!

Name the sense and the sensory Name the sense and the sensory organ in each of the photographs.organ in each of the photographs.

StimuliStimuli Sense Sense ((deriaderia))

Sensory Sensory organorgan

Touch, heat, cold, Touch, heat, cold, pain & pressurepain & pressure

ColdCold SkinSkin

Smell or odoursSmell or odours ChemicaChemicall

NoseNose

Sweet, sour, Sweet, sour, bitter & saltbitter & salt

ChemicaChemicall

TongueTongue

SoundSound SoundSound EarEar

Light (brightness Light (brightness or colour)or colour)

LightLight EyeEye

response

The way in which a living thing acts upon receiving a

stimulus

How would you respond How would you respond when you:when you:

(a)(a) hear the bell ring? hear the bell ring? (b)(b) eat hot and spicy food?eat hot and spicy food?(d) smell a marigold, a foul (d) smell a marigold, a foul

smelling flower?smelling flower?(e) see an empty plastic bag (e) see an empty plastic bag

lying on the floor in front of lying on the floor in front of you?you?

StimulusStimulus Receptors in Receptors in Sense organSense organ

NervesNerves BrainBrain

NervesNervesResponseResponse

Skin nerve

Brain nerveBrain nerve

Effectors Effectors

(Muscles, glands)(Muscles, glands)

1.11.1 Sensory OrgansSensory OrgansThe Pathway from Stimulus to ResponseThe Pathway from Stimulus to Response

The organ that detect touch sense is skin.

Skin give respond to stimuli like touch, pain, heat, cold and pressure.

Our skin is 2mm thick and consists of 2 layers which epidermis and dermis.

The sensitivity of the skin depends on the number of sensory receptors and the thickness of the epidermis.

EpidermisEpidermis(upper layer)(upper layer)

• made of dead cellsmade of dead cells

• waterproofwaterproof

• act as a protective layer to act as a protective layer to preventing the entry of bacteria preventing the entry of bacteria into the tissues.into the tissues.

DermisDermis(lower layer)(lower layer)

Consists of living cells, blood Consists of living cells, blood capillaries, nerve and sweat glandscapillaries, nerve and sweat glands

Consists receptor or nerve ending, Consists receptor or nerve ending, enable skin to detect stimulienable skin to detect stimuli

1.21.2 Sense of TouchSense of Touch11

Pain Pain receptorreceptor

Touch Touch receptorreceptor

Heat Heat receptorreceptor

Cold Cold receptorreceptor

PressurPressure e

receptorreceptorss

StimulusStimulus Receptors in Receptors in Sense organSense organ

NervesNerves BrainBrain

NervesNervesResponseResponse

How do the boy do after holding the hot pan? Describe the pathway from stimulus to respond.

1.31.3 Sense of SmellSense of Smell

NoseNose is the sensory organ of smellsmell..

Sensory cells are found in the upper roof of the nose cavity.

Smell from chemical substances dissolves in the mucus of the nose.

Mucus in the nose stimulates the sensory cells of smell and sends impulses to the brain through nerve cells.

Air Air

Sensory Sensory cellscells

Nasal Nasal cavitcavityy

NostrilNostril

How do our nose detect smell???...How do our nose detect smell???...

Smells are carried by certain Smells are carried by certain chemicalschemicals in the air. When we breathe, these in the air. When we breathe, these chemicals go through our nose. chemicals go through our nose.

It will then It will then dissolve in mucuos –dissolve in mucuos –the the moisture layer that covers the smell moisture layer that covers the smell receptors on the upper part of the receptors on the upper part of the nose. nose.

The dissolved chemicals The dissolved chemicals stimulatestimulate the the smell smell receptorsreceptors. .

The stimulated smell receptors then The stimulated smell receptors then send messages to the brain. The brain send messages to the brain. The brain identifies the smells.identifies the smells.

hearing

Chemical substance

Smell reseptors

dissolve in mucus Nerve

Brain(interpret the massage)

Nerves

Smell is identified

1.41.4 Sense of TasteSense of Taste

The The tonguetongue is the sensory organ of is the sensory organ of tastetaste..

Our tongue able to detect and Our tongue able to detect and differentiate different taste such as differentiate different taste such as sweetsweet

,, saltysalty,,

sour andsour and bittebitter.r.

When we eat or drink, foods or drinks When we eat or drink, foods or drinks dissolved in saliva are detected by the dissolved in saliva are detected by the taste receptors in our tongue.taste receptors in our tongue.

On the surface of tongue has groups of On the surface of tongue has groups of sensory cells called sensory cells called taste budstaste buds for for detecting different tastes. detecting different tastes.

Different areas of the tongue are more Different areas of the tongue are more sensitive to specific tastes. sensitive to specific tastes.

bitterbitter

sousourr

saltsaltyy

sweesweett

Chemical substance (food)

Taste reseptors

dissolve in saliva Nerve

Brain(interpret the massage)

Nerves

Taste is identified

All our senses work together, but the All our senses work together, but the sense of sense of smell smell and and tastetaste are special are special partners. When we eat, our nose smells partners. When we eat, our nose smells the food and our tongue gives us the the food and our tongue gives us the taste of the food. Together, they help taste of the food. Together, they help us to sense most, if not all, of the us to sense most, if not all, of the flavors contained in the food we eat. flavors contained in the food we eat.

Will the food taste as good as it Will the food taste as good as it normally does when our nose is normally does when our nose is blocked?blocked?

It difficult to taste the food you eat It difficult to taste the food you eat when you get a flu.when you get a flu.

1.51.5 Sense of HearingSense of Hearing

Ear is the sensory organ of hearing. Ear is the sensory organ of hearing.

Our ear has 3 main parts:Our ear has 3 main parts:a. the a. the outer earouter ear, filled with air, filled with airb. the b. the middle earmiddle ear, filled with air, filled with airc. the c. the inner earinner ear, filled with liquid, filled with liquid

Outer Outer earear

MiddlMiddle eare ear Inner Inner

earear

pinnpinnaa

ear ear cannalcannal

eardrueardrumm

ossiclossicleses

coclecocleaa

Eustachian Eustachian tubetube

auditorauditory nervey nerve

semicirculsemicircular canalsar canals

oval oval windowwindow

Part of earPart of ear StructureStructure FunctionsFunctions

Pinna Pinna Made of cartilage and skins. Made of cartilage and skins. Shape like a funnelShape like a funnel

Collects and directs sounds into the ear Collects and directs sounds into the ear canalcanal

Ear canalEar canal A long tube, lined with hairs A long tube, lined with hairs Directs sounds to the eardrumDirects sounds to the eardrum

Eardrum Eardrum A thin membraneA thin membrane Vibrates when sound waves hit itVibrates when sound waves hit it

Ossicles Ossicles Three small bones Three small bones Amplify vibrations and transfer them to the Amplify vibrations and transfer them to the oval windowoval window

Oval windowOval window A small, thin membraneA small, thin membrane Transfers vibrations of the ossicles to the Transfers vibrations of the ossicles to the cochleacochlea

Cochlea Cochlea A coiled tube, filled with fluid. A coiled tube, filled with fluid. Contains receptorsContains receptors

Detects vibrations and converts then into Detects vibrations and converts then into nerve implusesnerve impluses

Eustachian tube Eustachian tube A tube that connects the A tube that connects the middle ear to the throatmiddle ear to the throat

Equalises air pressure on both sides of the Equalises air pressure on both sides of the eardrum, preventing it from damageeardrum, preventing it from damage

Auditory nerveAuditory nerve Nerve fibers that connect to the Nerve fibers that connect to the brainbrain

Cariies nerve impulses to the brainCariies nerve impulses to the brain

Semicircular Semicircular canalscanals

Three semicircular canals Three semicircular canals situated at right angles to each situated at right angles to each other other

Detect position and movement of head to Detect position and movement of head to help us keep our balancehelp us keep our balance

How do we hear????How do we hear????

Pinna get sound

Auditory canal

Eardrum vibrate

Ossicles vibrate Oval window

Liquid in cochlea vibrate

Sound waves

Auditory nerve

1.81.8 Sound & HearingSound & Hearing

Sound produced by Sound produced by vibrations of an vibrations of an objectsobjects..When sound is produced kinetic energy is When sound is produced kinetic energy is changed to the sound energy.changed to the sound energy.

Sound can Sound can traveltravel through through solidssolids, , liquidsliquids and and gasesgases. Sound . Sound cannot travelcannot travel through through vacuumvacuum. . Sound travels faster trough solids than Sound travels faster trough solids than liquids or gases because the particles in a liquids or gases because the particles in a solid are very close together. solid are very close together.

Sound can be Sound can be absorbedabsorbed by a soft surface by a soft surface such as soft board on the walls of a cinema such as soft board on the walls of a cinema hall. hall. Soft and rough surfacesSoft and rough surfaces are good are good absorbers of sound.absorbers of sound.

Sound can be Sound can be reflectedreflected when sound hits when sound hits hard and smooth surfaceshard and smooth surfaces like walls. A like walls. A reflected sound is called an echo. A large reflected sound is called an echo. A large tunnel and a cave are examples that can tunnel and a cave are examples that can give out echoes.give out echoes.

Defects of hearing and ways to correct Defects of hearing and ways to correct themthem

Hearing loss can be occur from wax Hearing loss can be occur from wax blockage, a punctured eardrum, birth blockage, a punctured eardrum, birth defects or ear infections. defects or ear infections.

The damage is often temporary and can be The damage is often temporary and can be treated medically or surgically.treated medically or surgically.

Defects of hearing and ways to correct Defects of hearing and ways to correct themthem

Other hearing loss can be caused by the Other hearing loss can be caused by the processes of aging, bacterial infections, a processes of aging, bacterial infections, a severe blow to the side of the head, severe blow to the side of the head, extended exposure to loud sound or a extended exposure to loud sound or a tumour in the inner ear.tumour in the inner ear.

This damages cannot be treated medically This damages cannot be treated medically but can be corrected using hearing aids.but can be corrected using hearing aids.

Limitations of hearingLimitations of hearing

Our ears can only hear sounds which have Our ears can only hear sounds which have a frequency of about 20 Hz to 20 000 Hz. a frequency of about 20 Hz to 20 000 Hz. Different people have different ranges of Different people have different ranges of hearing. hearing.

Some devices that are used to overcome Some devices that are used to overcome the limitations of hearing such as the limitations of hearing such as earphones and stethoscopes.earphones and stethoscopes.

Stereophonic hearingStereophonic hearing

Stereophonic hearing is hearing with both Stereophonic hearing is hearing with both our ears.our ears.Stereophonic hearing helps us to determine Stereophonic hearing helps us to determine the direction from which a sound comes.the direction from which a sound comes.

1.61.6 Sense of SightSense of Sight

The The eyeeye is the sensory organ of is the sensory organ of sightsight and it is and it is sensitive to lightsensitive to light..

Human beings have a pair of eyes situated in the Human beings have a pair of eyes situated in the socket of the skull.socket of the skull.

Each eye is surrounded by fatty tissues.Each eye is surrounded by fatty tissues.

1.61.6 Sense of SightSense of Sight Cilialry Cilialry bodybody

ConjuctivConjuctiva a

1.61.6 Sense of SightSense of SightModel of a human eyeModel of a human eye

1.61.6 Sense of SightSense of SightModel of a cow eyeModel of a cow eye

1.61.6 Sense of SightSense of Sight

Light enter the eye through the Light enter the eye through the corneacornea and and aqueous humouraqueous humour to the to the pupilpupil and to and to the the lenslens of the eye. of the eye.

The convex lens focusses the light rays The convex lens focusses the light rays onto the onto the vitreous humousvitreous humous and the and the retinaretina to produce a clear image. to produce a clear image.

cornecorneaa

aqueous aqueous humourhumour

pupilpupil lenslens

vitreouvitreous s

humouhumouss

retinaretinaoptic nerveoptic nerve

The Formation of Images

How do we see?????????

1. Light rays travel from the object to eye

2. The light rays pass through the eye, they are refracted by some cornea, aqueous humour, lens and vitreous humour

3. An upside downimage (flag) is formed on the retina

4. The photoreceptors on the retina send nerve impulses along the optic nerve to the brain

5. The brain interprets the impulses and allows us to see the object

1.71.7 Light & SightLight & Sight

Light plays an important part in our life Light plays an important part in our life because without light we cannot see.because without light we cannot see.

The properties of light are:The properties of light are:

(a) its travels in straight lines.(a) its travels in straight lines.

(b) its can be reflected. (b) its can be reflected. (pantul)(pantul)

(c) its can be refracted. (c) its can be refracted. (bias)(bias)

Properties of Light

Light travels in a straight

Light can be reflected

Light can be refracted

Light can be dispersed

Light travels in Light travels in straight linesstraight lines. This causes . This causes the formation of shadows and eclipses of the formation of shadows and eclipses of the sun and the moon.the sun and the moon.

Light can be Light can be reflectedreflected. The image in a . The image in a plane mirror is due to the mirror reflecting plane mirror is due to the mirror reflecting light from the object to the observer. This light from the object to the observer. This is because the light bounces off the surface is because the light bounces off the surface of an object.of an object.

A smooth and shiny opaque surface A smooth and shiny opaque surface reflects more light than a rough surface.reflects more light than a rough surface.

The image in a plane mirrorThe image in a plane mirror

the angle of reflection = the angle of the angle of reflection = the angle of incidenceincidence

regular surface irregular surface

When light travels from one medium to When light travels from one medium to another, its speed changes. This causes the another, its speed changes. This causes the light to bend or change its direction means light to bend or change its direction means the light is the light is refractedrefracted. .

When light ray travels When light ray travels from a less densefrom a less dense medium (air) medium (air) to a more denseto a more dense medium medium (glass) the refracted ray (glass) the refracted ray bends towards the bends towards the normalnormal. .

mirror

raynormal

When light ray travels When light ray travels from a more densefrom a more dense medium (glass) medium (glass) to a less denseto a less dense medium medium (air) the refracted ray (air) the refracted ray bends away from the bends away from the normalnormal. .

mirrorair

normal

When light ray travels medium When light ray travels medium perpendicularly the light rayperpendicularly the light ray passes passes straight through the medium without being straight through the medium without being bent or refracted. bent or refracted.

mirrorair

raynormal

A stick which partly immersed in A stick which partly immersed in water to appear water to appear bentbent at the surface at the surface of the water.of the water.

Defects of vision and ways to correct themDefects of vision and ways to correct them

People who cannot see well are said to People who cannot see well are said to have defects in their vision.have defects in their vision.

The common defects of vision are:The common defects of vision are:• short sightednessshort sightedness, , •long-sightednesslong-sightedness,, •astigmatismastigmatism,, •colour-blindness colour-blindness and and •presbyopiapresbyopia

What do you see? Do you know what MYOPIA is?!

Short sightedness (myopia)Short sightedness (myopia)

Able to see near objects clearly but cannot Able to see near objects clearly but cannot see distant object.see distant object.

To correct this defect, the person has to To correct this defect, the person has to wear wear concave lensesconcave lenses..

SHORT SIGHTEDNESS

NORMAL VISSION SHORT SIGHTEDNESS

A distance object cannot be seen clearly A distance object cannot be seen clearly because the image is focused in front of the because the image is focused in front of the retina.retina.

This is because the eye lens is too thick or This is because the eye lens is too thick or the eyeball is too long.the eyeball is too long.

It is corrected by using a concave lens to It is corrected by using a concave lens to diverge the rays of light on the retina.diverge the rays of light on the retina.

NORMAL VISSION LONG SIGHTEDNESS

Do you see the difference? Is this what we call

HYPEROPIA?!

Long sightedness (Hypermetropia)Long sightedness (Hypermetropia)

A long sightedness person can see distant A long sightedness person can see distant objects clearly but cannot see near object.objects clearly but cannot see near object.

To correct this defect, the person has to To correct this defect, the person has to wear wear convex lensesconvex lenses..

A near object cannot be seen clearly A near object cannot be seen clearly because the image is focused behind of the because the image is focused behind of the retina.retina.

This is because the eye lens is too thin or This is because the eye lens is too thin or the eyeball is too short.the eyeball is too short.

It is corrected by using a convex lens to It is corrected by using a convex lens to converge the rays of light on the retina.converge the rays of light on the retina.

Astigmatism Astigmatism

Astigmatism is a common vision defect Astigmatism is a common vision defect caused by the irregular surface of the caused by the irregular surface of the cornea.cornea.

Things look blur to a person with Things look blur to a person with astigmatism.astigmatism.

This defect of vision can be corrected This defect of vision can be corrected using cylindrical lenses.using cylindrical lenses.

Now test your eyes for astigmatism by Now test your eyes for astigmatism by looking at the figure below. If one or more looking at the figure below. If one or more lines in the chart appears clearer and lines in the chart appears clearer and black but the others appear blurred, then black but the others appear blurred, then you have astigmatism.you have astigmatism.

astigmatism astigmatism imageimage

normal normal imageimage

Can you see the craters on the moon ?

Can you see microorganism in the air?

Limitation of Sight Limitation of Sight

Our sense or sight has its limitations. We cannot see objects that are very tiny, such as bacteria, viruses and atoms with our naked eye. We also cannot see the stars and planets that are very far from Earth.

Examples of limitations of sight are:(a) optical illusions(b) blind-spot

1.71.7 Light & SightLight & SightOptical illusionsOptical illusions

The image formed in the eye is accurate but The image formed in the eye is accurate but the brains plays a trick and makes the image the brains plays a trick and makes the image misleading.misleading.

Optical illusionsOptical illusions

Blind-spot (scotoma)Blind-spot (scotoma)

The blind spot is the point on the retina The blind spot is the point on the retina where the optical nerve leaves the eye.where the optical nerve leaves the eye.

Close your left eye and stare at the cross mark in the Close your left eye and stare at the cross mark in the diagram with your right eye. Now slowly move toward the diagram with your right eye. Now slowly move toward the diagram. Keep looking at the cross mark while you move. At diagram. Keep looking at the cross mark while you move. At a particular distance, the spot will disappear (it will reappear a particular distance, the spot will disappear (it will reappear again if you move even closer). The spot disappears because again if you move even closer). The spot disappears because it falls on the optic nerve head, the hole in the photoreceptor it falls on the optic nerve head, the hole in the photoreceptor sheet.sheet.

1.71.7 Light & SightLight & SightStereoscopic and monocular Stereoscopic and monocular vision vision

Stereoscopic Stereoscopic vision vision

Monocular visionMonocular vision

1.71.7 Light & SightLight & SightStereoscopic and monocular Stereoscopic and monocular vision vision

Stereoscopic visionStereoscopic vision Monocular visionMonocular vision

Location of the Location of the eyeeye

DifferencesDifferences

Size of the field Size of the field of visionof vision

Overlapping field Overlapping field of visionof vision

Importance Importance of visionof vision

ExamplesExamples

At the front of the headAt the front of the head

SmallSmall

Large area of overlapping Large area of overlapping fieldsfields

• Can estimate distance Can estimate distance accuratelyaccurately• see things in three see things in three dimensionsdimensions

Tigers, owl, human beingsTigers, owl, human beings

One on each side of the One on each side of the headhead

Very largeVery large

Small area or no Small area or no overlapping areaoverlapping area

• Can see predators in allCan see predators in all directionsdirections• cannot judge distance cannot judge distance accuratelyaccurately

Pigeons, rabbits, cows, fishPigeons, rabbits, cows, fish

1.71.7 Light & SightLight & SightDevices to Overcome the Limitations of SightDevices to Overcome the Limitations of Sight

Optical instruments

Used to study small objects Used to study small objects and specimens mounted on and specimens mounted on

slidesslides

Used to study Used to study stars in the stars in the

skysky

Used to Used to observe observe distant distant objectsobjects

Used by submarine to look Used by submarine to look out above the surface of the out above the surface of the

seasea

Used to scan and see the Used to scan and see the fetus of a pregnant motherfetus of a pregnant mother

CAT Scan

MRI Scan

1.91.9 Stimuli & Responses in PlantsStimuli & Responses in PlantsRespond in plants to stimulus is known as Respond in plants to stimulus is known as tropismtropism..

PhototropismPhototropism

•Def.: Respond of plant to light Def.: Respond of plant to light •+ve phototropism +ve phototropism Shoots Shoots grow grow towards lighttowards light•-ve phototropism -ve phototropism RootsRoots grow away grow away from lightfrom light•+ve phototropism helps green plants to +ve phototropism helps green plants to make food by photosynthesismake food by photosynthesis

1.91.9 Stimuli & Responses in PlantsStimuli & Responses in Plants

HydrotropismHydrotropism

•Respond to water by plantsRespond to water by plants

•+ve hydrotropism +ve hydrotropism Roots Roots grow towards grow towards waterwater

•-ve hydrotropism-ve hydrotropismShootsShoots grow away from grow away from waterwater

•+ve hydrotropism helps the roots to get +ve hydrotropism helps the roots to get waterwater

•Roots are attracted more by water than by Roots are attracted more by water than by gravity. gravity.

GeotropismGeotropism

•Respond to gravity by plantsRespond to gravity by plants

•-ve geotropism -ve geotropism ShootsShoots grow upwards grow upwards against gravityagainst gravity

•+ve geotropism +ve geotropism RootsRoots grow downwards grow downwards towards gravitytowards gravity

•+ve geotropism helps the roots to get +ve geotropism helps the roots to get water and to anchor the plants firmly into water and to anchor the plants firmly into the soil for supportthe soil for support

ThigmotropismThigmotropism

•Some plants with soft stems climb up Some plants with soft stems climb up a support when they touch ita support when they touch it

•They climb by twining, by using They climb by twining, by using tendrils or thorn/hookstendrils or thorn/hooks

•This This respond to touchrespond to touch by plants is by plants is called called thigmotropismthigmotropism

•Thigmotropism helps plants to get Thigmotropism helps plants to get sunlight for photosynthesissunlight for photosynthesis

Nastic movementsNastic movements

•A movement made by plants in response A movement made by plants in response to stimuli that may come in any directionto stimuli that may come in any direction

•The leaves of the The leaves of the mimosamimosa plant close up plant close up when they are touchedwhen they are touched

•A nastic movement response helps to A nastic movement response helps to protect the plant from injuryprotect the plant from injury

senses

touch sense

sense of smell nose

sense of sight

sense of hearing ear

sensory organs sensory

sense of taste thetongueis

sensory organ of smell

sensory cells of smell

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