The SensesThe Senses

Name the 5 Senses?Name the 5 Senses? TouchTouch SightSight TasteTaste SmellSmell HearingHearing

Each sense has receptor cells, these Each sense has receptor cells, these maybe neuron endings or specialised cells maybe neuron endings or specialised cells in close contact with neurons.in close contact with neurons.

ReceptorsReceptors

Are specialised to respond to various Are specialised to respond to various stimuli such as heat, light, pressure and stimuli such as heat, light, pressure and chemicalschemicals

All of the above are forms of energy & All of the above are forms of energy & receptors convert this energy into receptors convert this energy into electrical impulses that travel along electrical impulses that travel along neurons.neurons.

TouchTouch Skin contains receptors for touch & Skin contains receptors for touch &

temperaturetemperature

These are found in different concentrations in These are found in different concentrations in skin at various locations around the body.skin at various locations around the body.

E.g. very few in the heel of the foot compared E.g. very few in the heel of the foot compared to the elbow which has several (this is why to the elbow which has several (this is why parents use their elbow to test the temp of a parents use their elbow to test the temp of a babies bath.babies bath.

TasteTaste Receptors are located in taste buds. Which Receptors are located in taste buds. Which

are found on the top and sides of the tongue are found on the top and sides of the tongue & in some parts of the throat.& in some parts of the throat.

4 basic taste receptors4 basic taste receptors Sweet, bitter, sour & salt. (See diagram)Sweet, bitter, sour & salt. (See diagram)

Flavour of food is combination of taste, smell, Flavour of food is combination of taste, smell, texture & temp, hence when we have a cold texture & temp, hence when we have a cold food looses its taste.food looses its taste.

TasteTaste

SmellSmell The nasal cavity has 20 million neurons to The nasal cavity has 20 million neurons to

detect smell (olfactory neurons)detect smell (olfactory neurons)

These respond to over 50 different chemicals These respond to over 50 different chemicals in a gaseous state, which combine to in a gaseous state, which combine to produce 10,000 different smells.produce 10,000 different smells.

These receptors also adjust to a smell very These receptors also adjust to a smell very quickly & stop responding. Hence a smell quickly & stop responding. Hence a smell disappears after awhile. disappears after awhile.

SightSight

Part of EyePart of Eye FunctionFunction

ConjuctivaConjuctiva Thin memb, protests sclera Thin memb, protests sclera (inflammation=Conjunctivitis)(inflammation=Conjunctivitis)

ScleraSclera White of eye, lets no light in, is tough & holds White of eye, lets no light in, is tough & holds shape of eyeshape of eye

CorneaCornea Clear part of eye, allows light into eye & bends Clear part of eye, allows light into eye & bends toward retinatoward retina

ChoroidChoroid Layer which provides blood to eye & Melanin to Layer which provides blood to eye & Melanin to absorb lightabsorb light

RetinaRetina Contains light receptors (cones&rods), Pigment = Contains light receptors (cones&rods), Pigment = rhodopsinrhodopsin

FoveaFovea Only contains cones, region of sharpest visionOnly contains cones, region of sharpest vision

Blind SpotBlind Spot No rods/cones located here, nerve fibres leave eye No rods/cones located here, nerve fibres leave eye herehere

Part of EyePart of Eye FunctionFunction

Optic NerveOptic Nerve 126 million axons carry impulses from rods & 126 million axons carry impulses from rods & cones to braincones to brain

LensLens Changes shape to focus light on retinaChanges shape to focus light on retina

Ciliary MuscleCiliary Muscle Causes shape of lens to changeCauses shape of lens to change

IrisIris Coloured part of eye, Controls amount of light Coloured part of eye, Controls amount of light entering eyeentering eye

PupilPupil Opening in iris, lets light into eye, large opening Opening in iris, lets light into eye, large opening =dilated=dilated

Aqueous Aqueous HumourHumour

Salt solution which holds the shape of front of Salt solution which holds the shape of front of the eyethe eye

Vitreous Vitreous HumourHumour

Viscous fluid, supports eye by exerting pressure Viscous fluid, supports eye by exerting pressure outwardsoutwards

External muscleExternal muscle Eye is moved by 6 external musclesEye is moved by 6 external muscles

HearingHearing

Function of the EarFunction of the Ear Hearing & balanceHearing & balance 3 sections of ear (outer, middle & inner ear)3 sections of ear (outer, middle & inner ear)

Outer & middle ear filled with airOuter & middle ear filled with air Inner ear filled with fluid called lymph.Inner ear filled with fluid called lymph.

The Ear & HearingThe Ear & Hearing Sound caused by vibrations in the air.Sound caused by vibrations in the air.

Vibrations collected by outer ear, passed Vibrations collected by outer ear, passed through the middle ear (vibrations amplified) through the middle ear (vibrations amplified) and transferred to fluid in the Cochlea on inner and transferred to fluid in the Cochlea on inner ear.ear.

Cochlea contains receptors which are Cochlea contains receptors which are stimulated by pressure waves in lymph. These stimulated by pressure waves in lymph. These receptors cause electrical impulses to be sent receptors cause electrical impulses to be sent to the brain which interprets them as sound.to the brain which interprets them as sound.

HearingHearingPart of EarPart of Ear FunctionFunction

PinnaPinna Collects & channels vibrations into Auditory canalCollects & channels vibrations into Auditory canal

Auditory Auditory canalcanal

Carries vibrations to eardrum, wax secreted outside Carries vibrations to eardrum, wax secreted outside eardrum to trap dust & protect the eareardrum to trap dust & protect the ear

EardrumEardrum (tympanic membrane) vibrates due to air vibrations(tympanic membrane) vibrates due to air vibrations

OssiclesOssicles 3 tiny bones in middle ear that vibrate & amplify 3 tiny bones in middle ear that vibrate & amplify vibrations (hammer, anvil & stirrup)vibrations (hammer, anvil & stirrup)

Eustachian Eustachian tubetube

Runs from middle ear to throat, It equalises Runs from middle ear to throat, It equalises pressure on either side of eardrum (pops when we pressure on either side of eardrum (pops when we yawn)yawn)

CochleaCochlea Spiral tube (resembles snails shell) converts Spiral tube (resembles snails shell) converts pressure waves caused by vibrations into electrical pressure waves caused by vibrations into electrical impulses which travel to brainimpulses which travel to brain

CochleaCochlea Vibrations arrive at cochlea from stirrup which Vibrations arrive at cochlea from stirrup which

is attached to a membrane on the cochlea is attached to a membrane on the cochlea called the oval window.called the oval window.

Vibrations pass through OW & form pressure Vibrations pass through OW & form pressure waves in lymph in cochleawaves in lymph in cochlea

Pressure waves stimulate receptors which form Pressure waves stimulate receptors which form a structure called the organ of Cortia structure called the organ of Corti

Receptors send electrical impulses to brain Receptors send electrical impulses to brain Impulsestravel along auditory/cochlear nerve.Impulsestravel along auditory/cochlear nerve.

Round window allows pressure waves to Round window allows pressure waves to dissipate out of cochlea into air of middle ear.dissipate out of cochlea into air of middle ear.

The Ear & BalanceThe Ear & Balance Balance largely detected in Vestibular Balance largely detected in Vestibular

Apparatus in inner ear.Apparatus in inner ear. VA Consists of 3 semicircular canalsVA Consists of 3 semicircular canals Person who damages VA loses sense of Person who damages VA loses sense of

balance balance VA is filled with LymphVA is filled with Lymph Receptors in VA detect whether head is vertical Receptors in VA detect whether head is vertical

or not & other detect movement.or not & other detect movement. Receptors send impulses to cerebellum of brain Receptors send impulses to cerebellum of brain

through vestibular nerve.through vestibular nerve.

Corrective measures for Corrective measures for hearing disorderhearing disorder

DisorderDisorder Glue ear = surplus sticky fluid in middle ear Glue ear = surplus sticky fluid in middle ear

which blocks the Eustachian tube & prevents which blocks the Eustachian tube & prevents movement of eardrum & small bones in middle movement of eardrum & small bones in middle earear

CorrectionCorrection Mild cases= nose drops to unblock ETMild cases= nose drops to unblock ET Severe cases=small tubes called grommets Severe cases=small tubes called grommets

inserted which allow air into the middle ear & inserted which allow air into the middle ear & forces fluid down ET. Grommets eventually fall forces fluid down ET. Grommets eventually fall out themselves.out themselves.