1.5 Sense of Hearing

7/28/2019 1.5 Sense of Hearing

1/15

CHAPTER 1

THE WORLD THROUGH

OUR SENSES

1.5 : SENSE OF HEARING


2/15

SENSE OF HEARING

Detects the sound produced by vibrating objects.

Sensory organ of hearing: ear

The ear:

Has 3 parts:

the outer ear

The middle ear The inner ear


3/15

Structure and Function of The Ear

Outer ear Middle ear

Inner ear


4/15


Outer ear

Pinna

Collects and directs sounds into the ear canal

Ear canal

Directs the sounds to the eardrum EardrumVibrates and transfers sound wavesto the ossicles


5/15


Middle ear

Ossicles

Amplify vibrations of the sound waves andtransfer them to the oval window

Oval

window

Eustachian

tubeTransfer sound vibration from the ossiclesto the cochlea

Balances the airpressure on bothsides of the eardrum


6/15


Inner ear

Semicircularcanal

Auditorynerve

Cochlea

Controls the balance of the body

Converts sound vibrations intonerve impulses

Sends impulses

from thecochlea to thebrain


7/15

How do we ear?

Ear pinna Ear canal Eardrum Ossicles

OvalwindowCochlea

Auditorynerves

Brain

Receives and

collect soundwaves

Directs the

sound waves to

Amplify the

soundvibrations

Vibrates

The liquid vibrated

and stimulate thereceptor in

Receptor

produces nerveimpulses

Nerve impulses are carried

to the brain to beinterpreted


8/15

Question!

1. What is the sensory organ for hearing?

2. What is the structure of the ear that vibrates when it is hit bysound waves?

3. Name the structure of the ear that amplify sound vibrations .

4. Name the structure of the ear that detects vibration andchanges it into nerve impulses.

5. State 2 structures of ears that do not play any part in hearing.


9/15

CHAPTER 1

THE WORLD THROUGH

OUR SENSES

1.6 : SENSE OF SIGHT


10/15

The sense of sight

Detects light stimulus

Organ of sight : eye

Structure of the human eye: has 3 layers of tissues:

The sclera (outermost)

The choroid (middle)

The retina (innermost)

has eyelid protects the front of the eye.

The eyeball is held in the eye sockets of the skull bymuscles.


11/15

Cross-section of human eye

2

47

5

6

31

8 9 10

11

12

13

1415

1. Conjunctiva2. Cornea3. Aqueous humour4. Cilliary body5. Iris

6. Pupil7. Suspensory ligaments8. Eye lens9. Sclera10. Choroid11. Retina12. Yellow spot13. Optic nerve14. Blind spot15. Vitreous humour


12/15

How do we see?

Light rays travel fromthe object to the eye.

1As the light rays pass through the eye, they

are refracted by the cornea, aqueoushumour, lens and the vitreous humour

2

An upside down imageis formed on the retina.

3

The photoreceptors on the retinasend nerve impulses along theoptic nerve to the brain.

4The brain interprets the

impulses and allows us tosee the object.

5


13/15

How do we see?

Human eyes have the ability:

To focus on objects at different distances by changing thethickness of the lens.

To look at an object in different light intensity by changingthe size of the pupil.

When looking at distance objects: The ciliary body relaxes

The eye lens becomes thinner

When looking at near objects The ciliary body contracts

The eye lens becomes thicker


14/15

How do we see?

When we look at an object in bright day: The size of the pupil decreases

Less light can enter the eyes

When we look at an object in dim area:

The size of pupil increases

More light can enter the eyes


15/15

Documents

1.5 Sense of Hearing