1. Sense Organs: Eyes & Ears
Section 9.5 & 9.6

2. The Human Eye - Vision

3. 3 layers
Outside layer = Sclera
Middle layer = Choroid
Inside layer = Retina

4. Sclera Thick, white external layer that gives the eye its shape
Protective
Helps to absorb some of the light that hits the surface of the eye

5. Cornea
Transparent part of the sclera that covers the area where the light enters
Space behind the cornea is filled with a liquid called the aqueous humour which supplies it with nutrients

6. Choroid Middle layer of the eye
Coloured membrane that absorbs the light which is not absorbed by the sclera

7. Iris
Part of the choroid that opens and closes to change the size of the pupil
Coloured due to melanin pigments (blue eyes have less pigment)

8. Pupil
Hole in the iris through which light passes to enter the eye

9. Lens Clear, flexible structure behind the iris
Allows the eye to focus on objects & changes its shape depending on whether the object is near or far

10. Accomodation
Close objects: ciliary muscles contract, lens becomes thicker
Far objects: ciliary muscles relax, lens becomes thinner

11. Retina Internal layer Composed of photoreceptors
Also contains blood vessels that supply oxygen and nutrients to the eye
The empty space in the eye is filled with a liquid called the vitreous humour

12. Photoreceptors Fovea Centralis Concectrated region of cones
Require light to be stimulated
Identify colours
Rods
Sensitive to light
Cannot distinguish colours
Fovea Centralis
Concectrated region of cones
Found directly behind the center of the lens

13. Blind Spot
The optic nerve, located at the back of the eye is a gap in the retina
No rods or cones at this spot
Therefore, no image can be formed with the light that hits this spot

15. Find your blind spot!

16. Pathway of nerve impulse
Stimulus (light)
Photoreceptors
Bipolar cells (in the retina)
Optic Nerve
CNS (Occipital Lobe)
Pathway of nerve impulse

18. The Human Ear – Hearing & Equilibrium

19. 3 sections Outer ear: Pinna & auditory canal
Middle ear: Eardrum  Oval window
Inner ear: Vestibule, semicircular canals & cochlea

20. Pinna
External structure of the ear
“funnel” that collects sound

21. Auditory Canal
Channel that connects the external environment to the interior of the ear
Ends at the eardrum
Sweat glands produce earwax – traps foreign particles

22. Tympanic Membrane AKA: eardrum
Thin layer of tissue, separates outer ear from middle ear
Sound waves cause it to vibrate

23. Ossicles 3 small bones Malleus (hammer) Incus (anvil) Stapes (stirrup)
Amplify sound when they vibrate
Sound is passed from eardrum through ossicles to oval window (covered with a thin membrane – leads to inner ear)

24. Eustachian Tube
Channel that leads from the middle ear to the mouth & nose
Swallowing, chewing, yawning allow air to be released & pressure on either sides of the eardrum to be equalized

25. Vestibule Chamber in the inner ear
Involved in balance (static equilibrium)
Allows you to determine the position of your head

26. Semicircular Canals Channels filled with fluid
Involved in balance (dynamic equilibrium)
Allows you to identify body movement

27. Cochlea Shaped like a snail shell
Converts sound waves into nerve impulses

28. Organ of Corti Sound receptor located in the cochlea
Auditory nerves relay impulses from the cochlea to the temporal lobe