Exam 2: The Visual System Flashcards
Sensation
Detection of stimuli from the environment.
Perception
Interpretation of detected stimuli.
Light
Electromagnetic radiation that is visible to the human eye and serves as the primary stimulus for vision.
Photon
Elementary particle of light.
Cornea
The front-most part of the eye that refracts light.
Pupil
The hole in the center of the eye that allows light to enter.
Lens
The structure that refracts light to focus it on the retina.
Accommodation
The process by which the lens changes shape to focus on objects at different distances.
Retina
The back part of the eye where light is converted into neural signals.
Fovea
The small pit in the retina with the highest visual acuity.
Optic Disk
The spot where the optic nerve exits the eye, creating a blind spot.
Blind spot
The area of the retina where the optic nerve exits the eye, lacking photoreceptors and thus insensitive to light.
Photoreceptors
Cells in the retina that detect light (includes rods and cones).
Rods
Photoreceptors that detect low light levels and are responsible for peripheral vision.
Cones
Photoreceptors responsible for high-acuity and color vision.
Phototransduction
The process by which photoreceptors convert light into neural signals.
Horizontal Cells
Interneurons in the retina that inhibit adjacent photoreceptors.
Bipolar Cells
Neurons in the retina that receive input from photoreceptors and send signals to ganglion cells.
Amacrine Cells
Interneurons in the retina that modulate signals between bipolar and ganglion cells.
Vertical communication in the retina
The flow of visual information from photoreceptors to bipolar cells and then to ganglion cells.
Lateral communication in the retina
The processing of visual information across the retina via horizontal and amacrine cells, which modify signals through inhibition and integration.
Retinal Ganglion Cells
Neurons that receive input from bipolar cells and form the optic nerve.
Optic Nerve
The nerve that carries visual information from the retina to the brain.
Optic Chiasm
The point where the optic nerves cross and diverge to the brain.
Lateral Geniculate Nucleus (LGN)
A part of the thalamus that processes visual information from the optic nerve.
Optic Radiations
Axonal bundles that carry visual information from the LGN to the visual cortex.
Primary Visual Cortex (V1)
The region of the brain that receives and processes visual information.
Retinotopic Organization
The mapping of visual input from the retina to neurons in the visual cortex.
Dorsal Stream
The “where” pathway that processes spatial location and movement.
Ventral Stream
The “what” pathway that processes object identification and visual memory.
Color Vision Deficiency
A condition where one or more types of cone photoreceptors are dysfunctional.
Saccades
Rapid, jerking movements of the eyes to scan the visual field.
Convergence
The process by which multiple photoreceptors synapse onto a single bipolar or ganglion cell, affecting visual acuity and sensitivity.
Depolarization of photoreceptors
Occurs in the dark when photoreceptors release glutamate due to the open sodium channels in their membranes.
Hyperpolarization of photoreceptors
Occurs in response to light when sodium channels close, reducing glutamate release and initiating visual signaling.
Three types of cones
The three photoreceptor types in the retina—S-cones (blue), M-cones (green), and L-cones (red)—each sensitive to different wavelengths of light.
Receptive field
The specific area of the visual field that influences the activity of a particular neuron in the visual system.
Off-center bipolar cells
Bipolar cells that are inhibited by light in the center of their receptive field and excited by light in the surround.
On-center bipolar cells
Bipolar cells that are excited by light in the center of their receptive field and inhibited by light in the surround.
Edge detection
A fundamental process in visual perception that enhances contrast at borders, crucial for identifying object boundaries.
Lateral inhibition
A neural mechanism in which active neurons inhibit neighboring neurons to enhance contrast and sharpen edges in visual processing.
Opponent Color Processing
A theory of color vision stating that colors are perceived in opposing pairs (red-green, blue-yellow, black-white) due to retinal and neural processing.
Color afterimage
A visual illusion where exposure to a color causes a subsequent complementary color to appear when looking at a neutral surface.
Optic tracts
The nerve pathways that extend from the optic chiasm to various visual processing centers, including the thalamus and midbrain.
The thalamus
A brain structure that relays and processes sensory information, including visual input from the retina via the lateral geniculate nucleus (LGN).
Superior Colliculus
A midbrain structure involved in the coordination of eye movements, visual attention, and orientation toward stimuli.
Pretectal Area
A region of the midbrain that plays a role in controlling the pupillary light reflex.
Suprachiasmatic Nucleus (SCN)
A region of the hypothalamus that regulates circadian rhythms using light information received from the retina.
Secondary (Extrastriate) Visual Areas
Cortical regions beyond the primary visual cortex (V1) that process complex aspects of vision, such as motion (MT/V5) and object recognition.
Fusiform face area (FFA)
A region in the inferior temporal cortex specialized for recognizing faces and facial features.
Prosopagnosia
A neurological condition, also known as face blindness, in which individuals have difficulty recognizing faces.
Visual agnosia
A disorder in which individuals can see objects but cannot recognize or name them due to damage in higher visual processing areas.
Optic ataxia
A condition where individuals have difficulty reaching for objects under visual guidance due to damage in the dorsal stream of the visual pathway.
Blindsight
A phenomenon in which individuals with damage to the primary visual cortex can respond to visual stimuli without conscious awareness of seeing them.
