BOVINE EYE DISSECTION INTRO – Spring 10

Can humans or non-human animals see in the dark?

Light?

Waves of electromagnetic energy Photons = discrete particles of energy

Travel in space at high speeds (186,000/mi/second!)Measure in length nanometers (billionth of a meter)

So, we call these wavelenths

Visable to humans 380 – 760 nm

Visible Spectrum of Wavelength - Humans

*snakes see infrared

Anatomy of the Eye

4. Iris: muscle, control of light intake, color (melanin)

5. Pupil: hole in iris --dilates/contract based on available light

10. Optic Nerve

6. Lens: adjusts the eye’sfocus (20%) accomodation

2. Cornea: covers iris & pupil focusing begins (80%)

3. Anterior Chamber (aqueous): clear fluid nutrients/shape

7. Vitreous Humor: gives eyeball shape

1. Sclera: covering of eye

1.

8.

2.

3.

4.

5.

6.

7.

9.

10.

8. retina: transduction rods & cones

9. Fovea: acuity, cones

11. choroid

11.

Anatomy of the Eye Light entering the eye

Normal Vision

Problem in lens Cataracts protein clumping together

Problem in the macula (fovea)Macular Degeneration: loss of acuity and center vision

Anatomy of the Eye - Retina

Retina: PhotoreceptorsTransduction of light

Into electrical chemical Message

Instead of NT Binding to receptor…

Light cause cascade of Intercellular messages

…notice anything funky about the set up?

Ganglion Cell Axons form optic nerve

Cell Layers in the Retina

Duplexity TheoryRods (scotopic)-responsible for night vision-very sensitive to light (low levels)-found in the periphery of retina- more than cones- Provide monochromatic info (Achromatic)- Provides poor acuity- Night blindness

Cones (photopic): -responsible for day vision (sensitive to mod-hi light) - found in fovea - provides greater acuity - trichromatic – color vision - legally blind (day blindness)

Anatomy of the Eye – Blind Spot

blind spot

The blind Spot

1 million nerve fibers

Optic Tract1/2 axons go to right side of the brain1/2 go to left side of brain

Not the same in all animals – depending on location of eyes

Ex: Rabbits & Guinea Pigs

IPSI & CONTRALATERAL PATHWAYS

How does the signal get to the Visual Cortex?

VIA the Retinal Ganglion Cell Axons

OPTIC TRACT

OPTIC TRACT

Glaucoma: problem in the Anterior Chamber fluid there doesn’t drain correctly which puts pressure on the back of the eye especially the optic nerve

Damage to the optic nerve = Glaucoma