The Eye

Energy v. Chemical senses

Energy Senses Chemical Senses

Transduction• Transforming stimulus energy

(signals) into neural impulses.• Each sense has its own

process of transduction• Information goes from the

senses to the thalamus , then to the various areas in the brain.

• Example:Converting Light Rays into neural messages

Remember Ethan in Sky High. He changes his body to slime. Solid form to liquid form. Change from one form of energy to another. Click the picture to watch power placement.

Vision• Our most dominating

sense.• Visual Capture –

tendency to allow visual images to dominate our perception

• Example:In a movie theater tend to think voices are coming from the screen, rather than the speakers

Phase One: Gathering Light

Light reflecting off an object – add info

The Stimulus Input: Light Energy

• Wavelength – distance from one wave to the next

• Determines hue (color)

Phase One: Gathering Light

HUE• The length of the wave gives us it’s hue (color).• ROY G BIVExample:• Red = longest wavelength• Blue-violet = shortest wavelength

The Physical Property of Waves

Intensity•The amount of energy in a light wave, determined by amplitude or height•Height of a wave gives us it’s intensity (brightness).Example:The higher the height, the brighter the color•The lower the height, the duller the color

Wavelength

Phase Two: Getting the light in the eye

The EyeCornea – protects the eye and bends light to provide focusPupil – small adjustable opening in the center of the eye which

light enters Dilation of the pupil allows more light to reach the periphery of the retina

where the rods are located

Iris – ring of muscle tissue that controls the size of the pupil opening

Lens – transparent structure that focuses light onto the retina Accomodation - process by which the lens changes shape (curvature and

thickness) to focus near or far images on the retina

Retina – light sensitive, inner membrane of the eye containing rods and cones where the process of transduction occurs

Retina• Rods - receptor cells

– Black, white, gray sensitive– Peripheral vision– Twilight vision– Most light sensitive

• Cones – receptor cells– Color sensitive – distinguish different wavelengths of light– central vision– Daylight, well-lit– Fine detail– Less sensitive to Dim light

• Fovea - central focal point in the retina– Central vision– Cones– Fine detail

Rods versus Cones

Example: Peripheral vision and color vision

Optic Nerve

• Optic Nerve – nerve that carries neural impulses from the eye to the brain

• Blind Spot – point at which optic nerve leaves the eye– Blind spot = no receptor

cells

• Example:Pg. 127 in textbook Black dot and red car

Phase III: Transduction

Overview: cornea, iris, pupil, lens, retina, optic nerve, thalamus, occipital lobe, visual cortex, feature detector cells.

Transduction1. Rods and Cones convert light energy to electro

chemical neural impulses = transduction 2. Rods and cons synapse with neurons called bipolar

cells located in the retina– Cones hotline to the brain– Direct link between single cone to bipolar preserves fine detail

of cones message

3. Bipolar Cells transmit to ganglion cells (another type of neuron) whose axons form the Optic Nerve)

4. 1/2 axons in optic nerve crisscross (called optic chasm) sending impulses to opposite side of brain

Visual Problems• Farsighted – cornea too

flat or distance from cornea to retina too short

• Nearsighted – cornea too curved or distance from cornea to retina too long

• Astigmatism – irregularly shaped cornea (like a football instead of a baseball

What do you think is the most important part of the eye?

Why?• Cornea• Pupil• Iris• Lense• Retina• Rods• Cones• Fovea• Optic Nerve