chapter 11 sense organs

8/12/2019 Chapter 11 Sense Organs

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Sense organs

Perception



The receptorsStimuli are things that affect

our behaviour, e.g. Light,sound, temperature,

gravity, touch, pain and

chemical taste.

Sense organs have receptorsthat detect these stimuli



The eyeThe eyes receive light then

brings it to focus on theretina.

Cells in the retina detectscolour, and light. The braininterprets the impulses

passed to it by the eyes, thenproduces the pictures wesee.

The eyes are protected by the

eye brows prevent sweatand eyelids prevent dirt andstones from entering the eye.The eye ball is also in asocket that protects it fromknocks.



Structure of the eye.Sclera- the white of the eye.

Helps the eye to keep itsshape.

Conjunctiva- prevents grit

and other substances from

entering the eye.

Cornea – the transparent part

of the sclera.

Iris - the muscle that controlsthe size of the pupil.

Pupil- allows light to pass

through the eye.



Structure of the eye.Virteous and aqueous

humour –

the jelly like fluidthat helps the eye keep its

shape. They also bend the

light that enters the eye.

Lens - focus light on theretina.

Suspensory ligaments-

change the shape of the

lens.



The retinaThe retina is a thin

layer of sensitive

cells that convertlight to electrical

impulses.

The retina sends

impulses via theoptic nerve to the

brain. The optic

nerve pass out of

the eye throughthe blind spot (

the light sensitive

cells are absent).



The retinaThe light sensitive cells in the

retina are of two kinds.

The cones are sensitive to

colour and are affected by

high intense light.

The rods are sensitive toblack and white.

The fovea is the centre of the

retina. It contains cones

that give really good

details.



Colour blindnessColour blind persons only see

black, grey and white. This

occurs when the rods and

cones do not work

properly.

Red/green colour blindpersons cannot distinguish

between red and green .



The pupilThe pupil size gets smaller in

bright light and lager in

dim light.

This reflex action controls the

amount of light entering

the eye.Images formed on the retina

are inverted (upside

down). The brain then turn

them right side up.



Cause and correction of sight defectsSight defects are made better

by using glasses.

Long sightedness occurs

when near objects cannot

be seen properly. A convex

lens is used to help correctlong sightedness.

Short sightedness occurs

when far objects cannot be

seen properly. A concave

lens is used to correct

short sightedness.



The earThe ear is used for receiving

sound, detecting gravity andassist in balance.

The outer air collect sound waves

and pass to through the

auditory canal.The ear drum separates the

outer air from the inner ear.

Sound waves cause the ear

drum to vibrate. This vibration

is amplified by three small

bones called ossicles which

pass them to the inner ear.



The vibrations travel to

the inner air where

they are changed toelectrical impulses by

the COCHLEA. The

impulses are

transported to thebrain by the auditory

nerve.

The auditory centre of

the brain interpret the

impulses as sounds.



Gravity and BalanceThe semicircular canals

are located in the

inner ear above the

cochlea.

Each movement of the

head cause fluids inthe ear to stimulate

the semicircular

canal to coordinate

which muscle isneeded to keep your

balance.



The tongueTaste is detected by the taste

buds in the tongue. Thetaste buds detect four

basic taste, sour, sweet,

salt and bitter.

chapter 11 sense organs

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