1. List the five Special Senses:

SmellTasteSight

HearingEquilibrium

2. Explain how special sense receptors are arranged:

Eyes and Ears

Large complex sensory organs.

Taste buds and olfactory epithelium

Localized clusters of receptors

3. What actually causes us to “feel” our world?

“Our sensory inputs are OVERLAPPING! What we finally experience is a blending of stimulus effects.”

4, Of all of the sensory receptors in the body,how many of them are in the eyes?

5. How much of the adult eye can actually be seen?

Where is the rest of the eye??

“Cushioned by fat, and tucked away within the walls of the bony orbit.”

6. Label the following drawings of the eye:

7.Identify the following External eye Structures

Eye lids

Flaps of skin that close over the eye for protection.

Eye Lashes

Grows from the borders of the eye lids, collects dust and debris and prevents it from entering the eye.

Meibomin Glands

Modified sebaceous glands associated with the eyelid edges. Produces an oily secretion that lubricates the eye.

Ciliary glands

Sweat glands that lie between the eye lashes.

ConjunctivaDelicate membrane that lines the eyelids and covers part of the outer surface of the eyeball. Secretes mucus that lubricates the eyeball.

Lacrimal Apparatus

Group structure consisting of the lacrimal glands, lacrimal ducts, and the lacrimal sacs.

Lacrimal glands

Produces salty tears to wash the eye

Lacrimal ducts

.Drains the tears into the lacrimal sac.

Lacrimal Sac

Collects the tears from the lacrimal duct, and sends them to the nasolacrimal duct.

Nasolacrimal duct

Transfers the tears from the lacrimal sac to the nasal cavity.

8. Explain how the tears washes the eye:

Washes the eye

Salt water flushes trash out of the eye.

Protects the eye fromBacterial invasion

.

Antibodies and an enzyme called LYSOZOME found in the tears destroys most bacteria that try to enter the body through the eyes.

Causes Congestion And the Sniffles

.When tears spill over the eyelids and fill the nasal cavities.

9. What is the importance of crying?

Chemical Irritation

.Crying washes out the chemicals or dilutes it so that it doesn’t hurt as much.

Emotional Tears

Relieves Stress

10. Explain the role of the extrinsic muscles:

A) These are 6 muscles that produce Gross eye movementsB) They make it possible for the eye to follow a moving object.

11. Discuss the general anatomy of the eye:

A- The eye ball is a HOLLOW SPHERE!

B- Its wall is composed of three TUNICS .

(coats, coverings, layers)

C- Its interior is filled with fluids called HUMORS.

D- The lens, the main focusing apparatus of the eye, is supported upright within the eye cavity dividing the eye into two chambers.

Tunic #1“The Sclera”

a- White part of eye

b- in the center of the sclera, is a crystal clear dome called the cornea.

Tunic #2: “The Choroid Layer

a- Middle tunic, contains dark pigments to keep light from scattering.

b- Forms the colored part of the eye called the IRIS.

Tunic # 3: The Retinaa- is sensory tunic found at the back of the eye.

b-Functions like a movie screen

Tunic # 3: The Retinac- Lined with photoreceptors that are stimulated by the incoming light.

13. Discuss the following diseases:

Conjunctivitis

.bacterial infection of the Conjunctiva! Causes a diseases commonly called “Pink eye”

Watery Eyes

Cold or nasal inflammation often causes the lacrimal mucosa to become inflamed and to swell. This impairs the drainage of tears from the eye surface.

14. Identify the following structures of the internal anatomy of the eye

15. Identify by function and / or location the following internal anatomical structures of the eye.

CorneaTransparent window in the center of the sclera. Allows light to enter the eye. Acts like a “Windshield” over the pupil.

Ciliary body

Two smooth muscle groups that holds and changes the shape of the lens.

IrisColored part of the eye. A sphincter muscle that opens and shuts in order to allow a sufficient amount of light to enter the eye.

Pupil

The opening in the center of the iris.

Lens

A crystal biconvex structure used to focus incoming light..

Aqueous humor

Liquid between the lens and the cornea wall.

Vitreous humor

Gel between the lens and the retina wall.

Retina

Back of the eye. Lined with photoreceptors

Optic discSite where the optic nerve is attached to the eye. Called the blind spot because there are NO photoreceptors on that spot.

Fovea Centralis

Found lateral to the blind spot, it is the point of sharpest vision because it contains only cones.

16. Explain why the cornea is the only tissue in the body that can be transplanted from one person to another without fear of rejection:

The cornea has no BLOOD VESSELS; therefore, it is beyond the reach of the immune system.

17. Differentiate the two types of photoreceptors found on the retina:

Rods:

a- Most dense at the edge of the retina and decreases in number

as the center is approached.

Rods:

b- Allows us to see Black, White, and Gray tones.

Rods:

c- Allows us to see in dim light and at night.

Rods:

d- Gives us our peripheral vision, or

side vision.

Cones:

More Cones are found at the center, and they get fewer as you moe to the edges.

Cones:

Allow us to see in

Cones:

Allow us to see in Bright Light!

Cones:

Gives us our frontal vision.

18. Describe the neural layer of the retina:

a- light enters the eye and projects an upside down image on the retina.

b- Rods and cones are stimulated by the light!

c- Signal is transferred to the axons of ganglion cells that transfer the signal to the optic nerve.

19. Describe the major types of neurons composing the retina:

Rods and cones receive the incoming signal.

Transfers signal to:

Bipolar neurons which transfers it to:

Ganglion cells of the optic nerve.

Optic nerve carries the impulse to the brain.

Definition

Cannot see clearly at night or in dim light

Body Malfunction?

Anything that interferes with the metabolic processes of the rods.

Cause of Malfunction?

Lack of Vitamin “A” in our diet.

“Eat more carrots!”

21. Differentiate the three types of cones:

One type receives

blue!

One type receives Green!

One type receives

Red!

22. Explain how we see intermediate colors:

Impulses received at the same time from more than one type of cone by the visual cortex are interpreted as intermediate colors.

Examples of intermediate color formation:

1 2

Cone 1 sees Red

Cone 2 sees Blue

+

Brain sees Purple

1 2

Cone 1 sees Red

Cone 2 sees Green

+

Brain sees Yellow

1 2

All three cone types stimulated!+

Brain sees White

1 2

No cone stimulation?

Brain sees Black!

23. Explain color blindness:

a) Lack of all three cone types? TOTAL COLOR BLIND

B) Lack of 1 or 2 cone types? Partially color blind.

c) Some people do not know that they are color blind, because they have never known the missing colors!

d) Color blindness is genetically sex linked! Only MALES can be color blind.

24.What is the role of the lens?

To focus the incoming light onto the RETINA.

25. What is a CATARACT?

The soft flexible lens of our youth becomes hard and cloudy. The cataract must be surgically removed.

26. Discuss the Aqueous humor:

a) Clear watery fluid found in front of the lens. Similar to blood plasma.

b) Continually secreted by a special area of the Choroid.

c) Helps maintain pressure inside the eye

d) Provides nutrients for the lens and cornea.

e) The liquid of the aqueous humor is reabsorbed by the Canal of Schlemn and returned to the blood for recharging with nutrients and the removal of cellular waste.

27. Discuss the Vitreous humor:

a)Ball of jelly BEHIND the lens!

b)Prevents the eyeball from collapsing.

28. Disease Glaucoma

What?

Pressure inside the eye increases dramatically and begins to compress the retina and optic nerve. Causing pain and possible blindness.

Why?

Glaucoma begins slowly as the drainage of the aqueous humor becomes blocked.

Symptoms:

At first nothing!

Later signs include seeing halos around lights. Headache and blurred vision.

Test:

Uses a machine called a TONOMETER to measure the internal eye pressure.

Treatment?

Eye drops. Occasionally, surgery to enlarge the drainage channel.

29. Discuss how the emmetropic eye focuses the light:

a)NORMAL EYE!

b) Light passes into the eye, is focused by the lens, and the focal point is projected directly on the retina.

c) Image is clear and in focus!

29. Discuss how the Myopic eye focuses the light:

a) NEARSIGHTED!

B) Light passes into the eye, is focused by the lens, but the focal point is IN FRONT of the retina!

c) Can see clearly up close, but distant vision is blurry.

30. Discuss the Hyperopic eye:

a) FARSIGHTED!

b) Light passes into the eye focused by the lens, but the focal point is BEHIND THE RETINA.

c) What actually hits the retina is NOT IN FOCUS YET. BLURRY.

d) Can see far of, but up close is blurry.

31. What causes a person’s eye to be myopic or hyperopic?

Myopic = Nearsighted

a)Eyeball is too long

b)A lens may be too strong

c)The cornea may be too curved.

Hyperopic = Farsighted

a)Eye ball is too short

b)Lazy lens that won’t change shape

32. What is Astigmatism?

a) Unequal curvatures in different parts of the cornea or lens causes astigmatism.

b) In this condition, blurry images occur because rays of light are focused not as points on the retina, but as lines.

Special corrective lens are required specifically designed for the individual needing them.

33. Explain how the myopic eye can be corrected?

Concave lens are used to bend the light, so that it will focus on the retina after if passes through the lens

34. Explain how vision in the Hyperopic eye can be corrected:

A convex lens is used to bend the light so that the lens cn bring it to a focus on the retina.

35. Explain how the images are received by the brain:

a) The optic nerve in each eyeball receives the images from that eye’s field of view.

b) At the optic chiasma, the neural tracts CROSS! The impulses from the right eye enters into the left cerebral hemisphere.

The impulses from the left eye, enters into the right cerebral hemisphere.

c) In the OCCIPITAL LOBE, these two views are merged, and …we see!

What causes us to see

a) Each eye has its own field of view.

b) When we look at something, our right eye gives us one perspective, and the left eye gives us another perspective.

c) When our mind puts these two perspectives together …3 – D !!!!

Can we see in 3-D with just one eye?

What if we lose one eye due to injury?

You will only be able to see things flat, like looking at a picture in a book.

37. Explain our eye reflexes:

ConvergenceWhen we look at close objects, our lens muscles automatically adjust the shape of our lens by pushing it into a ball so we can see it.

Add this Reflex term!

DivergenceWhen we look at Far objects, our lens muscles automatically stretch the shape of our lens so we can see it.

Photopupillary Reflex

The iris automatically closes when the light is too intense; and automatically opens when the light is less intense

Accommodation papillary reflex

The pupils will constrict when we stare at close objects and open back up when we view distant things.

38. What is eye strain, and how can we avoid it?

Eye strain occurs when we read a lot, and the eye muscles stay busy tryng to keep the pupils constricted, and move the eye back and forth at the same time. They tire out.

Avoid eye strain?

Simple, look UP and STARE at DISTANT objects for a few seconds. This will rest the eyes.