All flashcards
Flashcard 1: What is the primary function of cones in the retina?
Answer: Color vision and high visual acuity in bright light (photopic) vision. Cones contain photopsins for detecting different wavelengths in bright conditions.
Flashcard 2: What is rhodopsin, and in which photoreceptor is it found?
Answer: Light-sensitive pigment in rods (opsin + retinal). The visual pigment undergoes conformational change when light hits retinal.
Flashcard 3: Which visual field information crosses at the optic chiasm: left or right visual field?
Answer: Both: nasal retinal fibers cross, carrying the contralateral visual field. Nasal fibers from each eye cross to process opposite visual fields.
Flashcard 4: What is the function of bipolar cells in the retina?
Answer: Relay signals from photoreceptors to ganglion cells. They form the middle layer of the retinal neural circuit.
Flashcard 5: What is binocular disparity, and what depth cue type does it represent?
Answer: Difference between the two retinal images; a binocular depth cue. Brain computes distance from horizontal image displacement between eyes.
Flashcard 6: What do retinal ganglion cell axons form as they exit the eye?
Answer: The optic nerve (cranial nerve II). Ganglion cells are the output neurons whose axons carry visual signals to the brain.
Flashcard 7: What structure creates the retinal blind spot by lacking photoreceptors?
Answer: Optic disc (optic nerve head). Where ganglion cell axons converge to form the optic nerve, no photoreceptors exist.
Flashcard 8: What retinal change occurs when light activates photoreceptors in phototransduction?
Answer: Photoreceptors hyperpolarize and reduce glutamate release. Light closes cation channels, causing hyperpolarization and decreased neurotransmitter.
Flashcard 9: Which pathway is the dorsal stream, and what is its main function?
Answer: Occipital-to-parietal “where/how” pathway for spatial location and motion. Guides actions and tracks movement through posterior parietal cortex.
Flashcard 10: Which pathway is the ventral stream, and what is its main function?
Answer: Occipital-to-temporal “what” pathway for object identity and form. Processes visual features for recognition in inferior temporal cortex.
Flashcard 11: What is the primary cortical area that first receives visual input from the LGN?
Answer: Primary visual cortex (V1, striate cortex) in the occipital lobe. V1 contains orientation-selective cells organized in columns.
Flashcard 12: What is the function of horizontal cells in retinal processing?
Answer: Lateral inhibition to enhance contrast via photoreceptor-bipolar modulation. They inhibit neighboring photoreceptors to sharpen edges and boundaries.
Flashcard 13: What are bipolar cells in the retina, in terms of information flow?
Answer: Intermediate neurons between photoreceptors and ganglion cells. They relay signals vertically through the retinal layers.
Flashcard 14: What retinal region provides the highest visual acuity?
Answer: Fovea (within the macula). Dense cone concentration provides sharp central vision.
Flashcard 15: What is the main function of cones in the retina?
Answer: Color (photopic) vision; lower sensitivity, high acuity. Cones contain opsins for detecting different wavelengths.
Flashcard 16: What is the main function of rods in the retina?
Answer: Dim-light (scotopic) vision; high sensitivity, low acuity, no color. Rods contain rhodopsin for detecting low light levels.
Flashcard 17: What is phototransduction in rods and cones?
Answer: Light converts signals in photoreceptors into neural activity. Photons trigger molecular cascades that hyperpolarize cells.
Flashcard 18: What is the key retinal neurotransmitter released by photoreceptors in darkness?
Answer: Glutamate. Darkness depolarizes photoreceptors, triggering release.
Flashcard 19: What is the functional difference between ON-center and OFF-center ganglion cells?
Answer: ON: fire to light in center; OFF: fire to darkness in center. Opposite responses create contrast detection mechanisms.
Flashcard 20: Identify the visual pathway order from retina to primary visual cortex (V1).
Answer: Retina → optic nerve → optic chiasm → LGN → optic radiations → V1. Visual signals relay through thalamus before reaching cortex.
Flashcard 21: At the optic chiasm, which retinal fibers cross to the opposite hemisphere?
Answer: Nasal retinal fibers decussate; temporal fibers remain ipsilateral. This crossing allows each hemisphere to process both eyes.
Flashcard 22: Which visual field projects to the left cerebral hemisphere?
Answer: Right visual field. Contralateral processing: each hemisphere sees opposite field.
Flashcard 23: Which visual field projects to the right cerebral hemisphere?
Answer: Left visual field. Visual fields project contralaterally after chiasm crossing.
Flashcard 24: What is the lateral geniculate nucleus (LGN) and where is it located?
Answer: Thalamic relay nucleus for visual input from retina to V1. Part of thalamus that processes visual signals before V1.
Flashcard 25: What is the primary visual cortex (V1), and where is it located?
Answer: First cortical visual area in occipital lobe (calcarine cortex). Receives LGN input for initial cortical visual processing.
Flashcard 26: What is retinotopic mapping in visual cortex?
Answer: Spatial layout of retina is preserved in V1 cortical representation. Neighboring retinal points map to neighboring cortical areas.
Flashcard 27: What is the function of the ventral visual stream (the “what” pathway)?
Answer: Object identity processing (form, color); projects to temporal lobe. Processes visual features to recognize objects and faces.
Flashcard 28: What is the function of the dorsal visual stream (the “where/how” pathway)?
Answer: Spatial location and motion processing; projects to parietal lobe. Analyzes movement and guides visually-directed actions.
Flashcard 29: What is the function of amacrine cells in retinal processing?
Answer: Modulate bipolar-to-ganglion signaling; motion/temporal processing. They integrate signals laterally for complex processing.
Flashcard 30: What structure is the optic disc, and what key feature does it create in vision?
Answer: Exit of optic nerve; creates the blind spot (no photoreceptors). Axons converge here, leaving no room for photoreceptors.