the senses reception of stimuli. 2 contents the senses organs classification of the senses...
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3 The Senses & Organs SenseOrgan Taste Smell Touch Hearing Sight Balance PressureTRANSCRIPT
The Senses
Reception of stimuli
2
ContentsThe Senses & OrgansClassification of the sensesInteroceptorsExteroceptorsHow they workTaste and Smell – smellTaste and Smell - taste
TouchEarHearingHearing defectsBalanceVisionEye – Parts & functionEye defectsVisual disorders
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The Senses & OrgansSense OrganTaste
Smell
Touch
Hearing
Sight
Balance
Pressure
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Classification of the senses
Classified according to type of stimulus to which they respond.
Two groups –Interoceptors
andExteroceptors
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Interoceptorsinteroceptors: sensory receptors that
respond to changes in the internal environment, e.g. stretch receptors in the muscles.
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Exteroceptorsexteroceptors: sensory receptors that
respond to external changes in the environment, e.g. taste receptors.
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Further division of receptors
Type of Receptor Responds to …
Chemoreceptor Chemicals e.g. taste
Photoreceptors Light e.g. rods & cones
Mechanoreceptors Physical change e.g. pressure
Thermoreceptors Temperature change
Proprioreceptors Movement of the body & position
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How they workThe sense organs contain receptors which
receive the stimuli and send messages to the brain along
sensory neurons. The brain acts as the interpreting centre for
received information.All nervous messages are the same.How they are interpreted by the various
parts of the brain is different.
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Taste and Smell - smellClosely related senses – chemoreceptors.
Chemicals enter the nose and stimulate the olfactory membranes in the back of the nose.
Different chemicals stimulate different receptors resulting in different “smells”.
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The
hum
an sm
ell
rece
ptor
s
What happens to your sense of
smell when you have a cold?
Why?
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Taste and Smell - tasteTaste buds in the tongue are similar.
They respond to chemicals dissolved in the mouth.
Sweet, sour bitter and salt – four basic tastes on different parts of the tongue.
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The
hum
an ta
ste
rece
ptor
s
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Tongue, rabbit, showing taste buds
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TouchFound in the skin.Involves the ability to sense a number of
stimuli e.g.Touch receptors – gentle force on hairless
skin – palm of handPressure receptors – greater force – found
all over the bodyPain receptors – found over the whole
skin.
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Vario
us se
nse
rece
ptor
s in
the
skin
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Skin of the scalp
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Skin, hair follicle,
sebaceous gland
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Skin, sweat glands
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EarDivided into three sections: -
Outer - Air filled - up to eardrumMiddle - Air filled - to oval windowInner - Fluid filled - cochlea
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Hearing (1/3)
hearing: perception by the brain of the action of sound on the eardrum.
Sound picked up by pinnaFunnelled into ear canalStrikes off eardrum (tympanum)Eardrum vibratesPressure on both sides of the eardrum is
kept the same by the Eustachian tubeThis connects the middle ear to the throat.
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The
hum
an e
ar
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Hearing (2/3)
This is why your ears ‘pop’ with sudden pressure changes e.g. airplane take off.
Vibration of eardrum passed on to the ear ossicles and amplified twentyfold by them (hammer, anvil, stirrup).
Stirrup connected to oval window which leads into the cochlea – a coiled fluid filled tube.
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The
hum
an e
ar
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Hearing (3/3)
In the cochlea the vibrations are converted into nerve impulses and transmitted along the auditory nerve to the brain where they are interpreted as sound.
The vibrations pass along the cochlea and are lost back to the middle ear at the round window.
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Hearing defects (1/2)
Usually caused by damage to the receptors in the cochlea.Continuous loud noise – pneumatic drills, rock concerts, listening to loud musin on earphones.Sudden very loud noise (gunshot)Some loss of receptors occurs with age
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Hearing defects (2/2)
Problems with outer or middle eare.g. glue ear in young children (usually of
smokers) – sticky fluid in middle ear – inserting drainage tubes into ear usually cures this.
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Balance A function of the inner ear – the semi-
circular canals.Fluid filled structures that detect
movement and position of the head.They are used to keep you balanced.
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Visionvision: the sensation resulting from the
stimulation of the light receptors in the eye that allows the shape and colour of an object to be perceived – the sense of seeing, sight.
The eye contains photoreceptors.
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A section through the eye
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Whole
eye,
mammali
an
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Parts and function (1/6)
Eyebrow – directs sweat away from eye.
Eyelid – blink - keep eye clear and moist.
Eyelashes – trap dust and dirt.
Conjunctiva – transparent membrane covering front of eye.
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Parts and function (2/6)
Lacrimal glands – produce tears - wash away dust and bacteria.
Sclerotic coat (sclera) – maintains eyeball shape, strong, opaque and provides muscle attachment.
Cornea – transparent part of sclera -
allows light to enter eye.
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Parts and function (3/6)
Choroid – dark in colour - prevents light reflection in the eye - contains blood vessels.
Retina – light sensitive layer, contains Rods (dim light) and Cones (colour vision).
Ciliary body – contains muscles, which
alter the shape of the lens.
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Parts and function (4/6)
Lens – transparent - biconvex - focus light on retina.
Suspensory ligament Attaches ciliary body to lens - helps control / adjust shape of lens
Iris – coloured part of eye - controls the
amount of light entering the eye.
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Parts and function (5/6)
Pupil – hole in centre of Iris through which light enters eye.
Aqueous humour – clear liquid found between lens and cornea - maintains eyeball shape.
Vitreous humour – jelly like substance
found between lens and retina - maintains eyeball shape.
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Parts and function (6/6)
Optic nerve – transmits messages from eye to brain.
Blind spot – where optic nerve leaves
eye - no rods or cones on retina => no vision at this spot.
Fovea – area of most acute vision on
retina - directly behind centre of lens.
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Eye defects
COMMON NAME
MEDICAL TERM DIAGNOSIS DEFECT SOLVE BY
WEARING
LONG SIGHT
Hyperm-etropia
Cannot see near objects
Eyeball too
short
Convex lenses
SHORT SIGHT Myopia
Cannot see distant
objects
Eyeball too long
Concave lenses
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Long-s
ighted
ness
and i
ts cor
rectio
n
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Short
-sighte
dness
and i
ts cor
rectio
n
Visual disorders
Not examinablefor information only
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Visual problems
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Glaucoma
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END