The Visual Sense: Sight EQ: What is the process though which we see and how do we differentiate between different objects and types of motion?

Visible Light: Wavelength The key to vision is light, however, we cannot however see all light Only electromagnetic radiation with a wavelength between 400 nanometers and 750 nanometers is within our visible spectrum All other light is invisible to the naked eye Wavelength determines color

Visible Light: Intensity The intensity of a light is determined by the amount of energy the light contains The more energy, the brighter the light

Step 1: Accessory Structures of Sight: Cornea Accessing light begins with the Cornea This curved, transparent layer protects our eyes and allows light to enter the rest of our eye

Step 1: Accessory Structures of Sight: Pupil This opening, directly behind the cornea, allows light to pass into the rest of the eye. The Pupil has the ability to contract or expand in order to allow less or more light into the eye.

Step 1: Accessory Structures of Sight: Iris The Iris can expand and contract to adjust the amount of light that enters the eye This contraction and expansion change the size of the Pupil The Iris determines our eye color

Step 1: Accessory Structures of Sight: Lens The lens, which is situated behind the pupil bends the light This light is focused onto the Retina Because the light bends, the object gets turned upside down and backwards.

Step 1: Accessory Structures of Sight: Retina The light from all the other accessory structures ends up on the retina where it is ready for transduction

Step 2: Receptor Structures of Sight: Rods Rods, which are photoreceptors, are placed toward the rear edges of the retina They are highly sensitive to light, but not to color. They allow us to see even in low light situations.

Focus on Dark Adaptation

Step 2: Receptor Structures of Sight: Cones Cones are photoreceptors that are designed to help distinguish color Cones are filled with photopigments that respond to certain spectrums of light

Focus on the Fovea The cones are found in the rear middle of the retina in an area called the Fovea Our ability to see clearly (Visual Acuity) is greatest in the Fovea.

Step 3: Sensory Nerves of Sight: Optic Nerve Once the information has been coded during transduction, the information travels up the Optic Nerve to the Thalamus.

Steps 4/5: In the Brain Once in the Thalamus, the neural impulse is sent to the Primary Visual Cortex within the occipital lobe Within this structure, the neural impulse is decoded (Perceived) and decisions based on behavior occur

Seeing Color: Hue Hue represents the essential color, which is determined by the dominant wavelength of the light.

Seeing Color: Saturation Saturation refers to how pure the color is represented

Seeing Color: Brightness Brightness refers to the overall intensity of all the wavelengths of the light together

Visual Representations: Feature Detectors Cells in the visual cortex that respond to a specific feature of an object. These detectors help define shape, color, direction, and other features of objects.

The Trichromatic Theory of Color This theory claims that all color vision is made up of three types of visual elements Each of these features is most sensitive to different wavelengths of light This takes place within our cones in our retina

Cones and the Trichromatic Theory: Each type of cone is sensitive to a different type of stimulus -Short Wavelength Cones: Respond most to blues -Medium Wavelength Cones: Respond most to greens -Large Wavelength Cones: Respond most to reddish-yellow WHY???

The Opponent-Process Theory of Color This theory claims that all color vision is made up of color sensitive visual elements These are made up of red- green, blue-yellow, and black-white elements Like the Trichromatic Theory, this also is a function of our cones

The Opponent-Process Theory of Color

Color Blindness: Some people are born with faulty cones containing only 2 of the 3 photoreceptors. If this happens, a person will suffer from color blindness