2. the visual system II Flashcards
(16 cards)
Where is the highest density of photoreceptors located in the retina?
In the fovea
The fovea is the center of the visual field and contains predominantly cone photoreceptors.
What type of photoreceptors dominate the peripheral retina?
Rods
Rods are responsible for low-light vision and are more numerous in the peripheral regions of the retina.
What is the primary function of cones?
Daylight vision (photopic conditions)
Cones are responsible for high-resolution and color vision in well-lit conditions.
How do rods and cones differ in sensitivity to light?
Rods are more sensitive; cones require 100x more light
This difference is crucial for their respective functions in low and high light conditions.
What are the two major types of retinal ganglion cells?
ON-center and OFF-center cells
These cells provide complementary information about the visual scene.
What happens to photoreceptors when light hits them?
They hyperpolarize
This hyperpolarization leads to different responses in bipolar cells.
What type of receptors do OFF-center bipolar cells use?
AMPA receptors
These receptors are excitatory and respond to the hyperpolarization of photoreceptors.
What is the role of horizontal cells in the retina?
Provide negative feedback to photoreceptors
This helps in detecting background illumination levels.
True or False: Ganglion cells are responsive to edges in the visual field.
True
They are particularly sensitive to edges and boundaries, enhancing visual perception.
What is the primary target area of retinal ganglion cells in the brain?
Lateral geniculate nucleus (LGN)
The LGN is involved in visual processing and has a layered structure.
What does the visual cortex maintain?
Spatial organization of the visual field
It processes information from both eyes to create a unified visual perception.
Fill in the blank: Rods have a _______ concentration of pigment for greater sensitivity.
Higher
This higher concentration allows rods to be more sensitive to light.
What is the effect of edge enhancement in visual perception?
Creates visual illusions
For example, uniform gray bars can appear shaded due to edge detection.
What type of visual conditions do rods primarily function in?
Scotopic conditions (night vision)
Rods are adapted for vision in low-light environments.
How do ON-center bipolar cells respond to photoreceptor hyperpolarization?
They depolarize
This is a sign-inverting response, contrasting with OFF-center bipolar cells.
What is the significance of retinotopic mapping in the LGN?
Maintains spatial arrangement of visual input
This organization allows for accurate visual processing based on the location of stimuli.
