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: 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

Phase One: Gathering Light

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:

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:

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

The Retina Rods and Cones RodsCones Rods Cones

Rods versus Cones

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:

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

Phase IV: In the Brain Thalamus to Occipital lobe to Visual Cortex to… Feature Detectors –nerves cells in the brain that respond to specific features – line, curve, shape color Example: Supercell clusters – teams of cells that fire in response to complex patterns Example: Example: Feature Detector cells – allow you to see the lines, motion, curves and other features of this turkey.

Parallel Processing Parallel Processing – brain simultaneously process stimulus elements Example: Blindsight – localized area of blindness in part of their field of vision caused by damage to visual cortex Example:

Color Vision Two Major Theories

Trichromatic Theory Three types of cones: Red Blue Green These three types of cones can make millions of combinations of colors. Does not explain afterimages or color blindness well.

Opponent-Process theory The sensory receptors come in pairs. Red/Green Yellow/Blue Black/White If one color is stimulated, the other is inhibited. Example:

Afterimages