The Eye

Energy v. Chemical senses Energy SensesChemical 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.

VisionVision 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 BIV Example: 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 Eye Cornea – protects the eye and bends light to provide focus Pupil – 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.

Transduction 1.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