Transcript Document

The Senses
Chapter 35
5 senses --- touch , taste, smell, sight &
hearing
TOUCH
The skin is the organ of touch
Touch is a combination of pain, pressure, hot & cold
 TASTE
The tongue is the organ of taste
Receptors for taste are located in the taste buds
Sweet--- tip of tongue
Salt--- sides of tongue near front
Sour--- sides of tongue near back
Bitter--- across back of tongue

•SMELL
The nose is the organ of smell
The Olfactory neurons in the
nose detect smell
•SIGHT
The eye is the organ for sight
The Eye
PART
FUNCTION
conjunctiva
protection
sclera
Lets no light through
Holds the eye in shape
cornea
Lets light into the eye
choroid
Nourishes eye &
prevents reflection of
light with in eye
Fovea (yellow spot)
Contains cones only–
region of sharpest vision
Blind spot
Where optic nerve leaves
the eye
Optic nerve
Carries impulses from
the eye to the brain
Lens
Changes shape to focus
light on the retina
Ciliary muscle
Cause the lens to change
shape
Iris (coloured part)
Controls the amount of
light entering the eye
Pupil
Lets light into the eye
Aqueous Humour
Holds the front of the
eye in shape
Retina
Contains rods & cones
(the light receptors)
Rods for black & white
vision & work in dim light
Cones for colour vision &
work in bright light
Vitreous Humour
Holds the back of the eye
in shape
Long Sightedness--Hypermetropia
Person with long sight can see distant
objects clearly, but cannot see near
objects
 Cause: eyeball is too short
 To Fix: use CONVEX lens

Short sightedness--- Myopia
Person can see near objects clearly, but
cannot see distant objects
 Cause: the eyeball is too long
 To Fix: use CONCAVE lens

Accommodation

Is the ability of the eye to focus light from
objects at different distances by altering
the focal length of the retina
Response of Iris to light

BRIGHT LIGHT
the circular muscles contract
the size of the pupil decreases
Less light enters the eye

DIM LIGHT
The circular muscles relax
The size of the pupil increases
More light enters the eye
Hearing


1.
2.
3.
The function of the ear is hearing and
balance
There are 3 sections to the ear
Outer ear
Middle ear
Inner ear
The Ear
PART
FUNCTION
Auditory canal
Collects vibrations & carries
vibration to eardrum
Carries vibration to the
middle ear
Eardrum
Ossicles– hammer, anvil,
stirrup
Eustachian tube
Increases the vibrations &
passes them to the oval
window
Connects the middle ear &
pharynx
Equalises pressure between
the middle & outer ear
Cochlea
Organ of Corti
Hearing– contain
receptors which are
stimulated by pressure
waves in lymph.
Receptors cause
electrical impulses to be
sent to the brain along
the auditory nerve which
interprets them as sound
Contains receptors for
hearing
Pinna
Collect and channel
vibration into the
auditory canal
Vestibular apparatus
Balance
How we hear
Sound waves enter the ear
 Eardrum vibrates
 Three bones amplify the sound
 Oval window vibrates
 Liquid in cochlea moves
 hair cells stimulated
 Auditory nerve carries impulses to the
brain
 Brain interprets the sound

Glue Ear
Is a hearing disorder
 Caused: by too much sticky fluid in the
middle ear
 Corrected: by decongestants or
grommets( small tubes inserted into the
eardrum)
