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Contents
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The Sensory ofThe Organ .
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The Sensory Organs !
The sensory organs > enable an organism to detect changes that occur in its
environment .
Five main sensory organs in humans and stimuli they respond to are shown in table
below >
Sensoryorgan Sense StimuliTouch Heat , pressure , pain ,
cold , touch
Smell Chemical subtances
Taste Chemical subtances
Sight Light
Hearing Sound
FunctionEnable us to feel and identify t
size , texture and shape of the
object
Detect various temperatureRemove waste substances in th
form of sweat
Detect various smell
Taste different flavoured prod
To see objects
Detects sound and help to bala
the body
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The pathway from stimulus to response >
Stimulus Receptors in sensory organs
Sensory nerves Motor nerves
Effectors Response
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Senseof
Touch
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Sense Of Touch !( skin)*the largest sensory organ in human body .*Very sensitive to touch .*The structure of the skin .*The skin consists of two main layers > epidermis & dermis .*Our body have different types of receptors >pain receptors
> touch receptors
> heat receptors
> cold receptors
> pressure receptors
*The receptors are connected to nerves .
*When a receptor is stimulated , an impulse is produced and sent through the nervous
system to the brain to be evualated .
*The sensitivity of skin > different parts of body have different degrees of sensitivity .
a) Thickness of the epidermis
> The thicker the epidermis , the lower the sensitivity of skin
>The thinner the epidermis , the more the sensitivity of skin .
b)The number of receptors
>The larger the number of receptors , the higher the sensitivity of skin .
> The smaller the number of receptors , the lower the sensitivity of skin .
c) Example : more sensitive >
: less sensitive >
Lips FingertipsNeck Back o
ha
toungue
ElbowSoles ofthe feet
LegsBack ofthe body
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* Advantages >
>
Reading Braille
> the blind use their fingertips to identify letters and
read Braille .
> this book used raised dots to represent numbers and
words .
The injection spot on the body
> doctors usually give injection at the forearm or the
hip .
> this area have few receptors and thicker epidermis .
> hence , less pain is felt by the patient .
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Sense oSmell
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Sense of Smell ! ( nose)# Smell > chemical present in the air
> chemical substances that give out air : food
: perfume
: flower
# Smell receptors > located at the roof of nasal cavity to allow the smell receptors have
the maximum exposure to the air current .
# Nervous pathway for detecting smell >
The brain interprets the impulses and the smell is
identified
Smell receptors are simulated
The smell receptors produce
nervous impulses
Chemical dissolve in the mucus
Chemical in the air enter the nasal cavity
Nervous impulses are sent to the brain
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# The Sensitivity of Smell > higher in animal :
Rat cat dog
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Sense oTaste
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Sense of Taste ( toungue )Sensory receptors . taste buds on the surface of tongue.Main types of taste . sour , salt , sweet and bitterTaste buds for detecting different types of taste are concentrated at different
parts of toungueGood taste of food > can only detected if the food is in the form of liquids or can
be dissolved by the salivaNervous pathway for detecting taste >
The brain interprets the impulses and the taste is identified .
Nervous impulses are sent to the brain .
Sensory cells produce nervous impulses .
Chemicals stimulate the sensory cells in taste buds .
Chemical dissolve in saliva .
food
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Sense of
Hearing
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Sense of Hearing ( ear)Sense of hearing > ability of the ear to detect the stimulus of sound .
Sense of balancing > ability to detect changes of the position of the body .Mechanism of hearing >
Pinna
Auditory canal
Eardrum
Cochlea
Ossicles
Oval window
Auditory nerve
Brain
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Senseof
Sight
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Sense of sight ( eyes)The human eyeball > spherical in shapenand lies in the eye socket .
The movements of the eyeball > controlled by three pairs of extrinsic muscles .
The mechanism of sight >
Light
Cornea
Aqueous humour
Vitreous humour
Optic nerve
Retina
Brain
Lens
pupil
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Christina Perri A Thousand YearsHeartbeats fastColors and promisesHow to be braveHow can I love when Im afraid to fallBut watching you stand alone
All of my doubt suddenly goes away somehowOne step closer
I have died everyday waiting for youDarling dont be afraid I have loved youFor a thousand yearsIll love you for a thousand more
Time stands still
Beauty in all she isI will be braveI will not let anything take awayWhats standing in front of meEvery breathEvery hour has come to thisOne step closer
I have died everyday waiting for youDarling dont be afraid I have loved youFor a thousand yearsIll love you for a thousand more
And all along I believed that I would find youTime has brought your heart to meI have loved you for a thousand yearsIll love you for a thousand more
One step closerOne step closer
I have died everyday waiting for youDarling dont be afraid I have loved youFor a thousand years
Ill love you for a thousand more
And all along I believed I would find youTime has brought your heart to meI have loved you for a thousand yearsIll love you for a thousand more
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Plug In stereo Oh Darlingyou seem quite nice for a girl with good looks
And Im the kinda fellow thatll make you feel better when your life gets shook
So give it a chance according to your plans
I bet I'm not number one on your list to kiss, but please understand
You seem quite shy, but youre oh so cute
And Im the kind of girl that would love to be yours if you'd asked me to
So just take a chance, try to hold my hand
I swear Id never let go
Just let me know if youd be my man
I really want to come out and tell you
Oh darling, I love you so
If youd ask me for my heart, theres no way that Ill say no
Oh darling, just take a chance pleaseSo we can stay together till hell starts to freeze
You seem quite right for a boy like me
And I wanna know would you treat me well
Would you treat me like a queen
Cause Id like to show you and make you see
That although were different types
We were meant to be
I really want to come out and tell you
Oh darling, I love you so
If youd ask me for my heart, theres no way that Ill say no
Oh darling, just take a chance please
So we can stay together till hell starts to freeze
So I gotta ask you,
I cant be afraid
I gotta take a chance at love
So what do you say
Oh darling, I love you so
If youd ask me for my heart, theres no way that Ill say no
Oh darling, just take a chance pleaseSo we can stay together till hell starts to freeze
Oh darling, I love you so
If youd ask me for my heart, theres no way that Ill say no
Oh darling, just take a chance please
So we can stay together till hell starts to freeze
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Light And SightLight travels in straight lines.
When light falls on dull surface, part of the light is absorbed and part of it
reflected.
Rate of reflection depends on > the colour of the surface
>the condition of the surface
Reflection of light can be used in the following
a) Periscope > a device that can be used to see over or around opaque object .It can be also used in submarines.
b) Kaleidoscope > a device that is able to produce beautiful and colourful imageswhen small objects are put into it .
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