1. the visual system Flashcards
(21 cards)
What are the three layers of the eye?
Sclera, Choroid, Retina
The sclera is the outer protective layer, the choroid is the middle vascular layer, and the retina is the inner sensory layer containing photoreceptors.
What substance fills the eye?
Vitreous humor
The vitreous humor is a clear, jelly-like substance that fills the eye.
Which part of the eye provides most of the light refraction?
Cornea
The cornea provides most of the light refraction and is non-adjustable.
What role does the lens play in light refraction?
Provides additional refraction and is adjustable via ciliary muscles
The lens can change shape to focus light, adjusting the refraction.
What is presbyopia?
Decreased ability to accommodate with age
Presbyopia is a common vision problem that occurs as people age.
What is myopia?
Nearsightedness where the eyeball is too long
In myopia, images are focused in front of the retina.
What is hyperopia?
Farsightedness where the eyeball is too short
In hyperopia, images are focused behind the retina.
What occurs at the optic chiasm?
Most fibers cross to the opposite side of the brain
This crossing supports binocular vision and depth perception.
What is the primary relay point for visual information?
Lateral geniculate nucleus
The lateral geniculate nucleus is crucial for processing visual data.
Which area of the brain is primarily involved in visual processing?
Visual cortex
Approximately 40% of the cortical area is involved in visual processing.
What is the organization of the retina?
Inverted organization
Light must pass through multiple cell layers before reaching photoreceptors.
What creates a blind spot in the retina?
Optic nerve
The optic nerve creates a blind spot where it passes through the retina.
What are the main cell types found in the retina?
Photoreceptors, Bipolar cells, Ganglion cells, Horizontal cells, Amacrine cells
These cells play essential roles in processing visual information.
What is the primary function of rods?
Function in low light, extremely sensitive
Rods can detect single photons but do not discriminate color.
What is the primary function of cones?
High spatial resolution, color discrimination
Cones require more light than rods and are responsible for color vision.
What are the three types of cones in human vision?
Short wavelength (blue), Medium wavelength (green), Long wavelength (red)
These correspond to approximately 420nm, 530nm, and 560nm respectively.
What is color blindness more common in males?
Medium and long wavelength cone genes are on the X chromosome
This genetic factor contributes to the higher incidence of color blindness in males.
What happens during phototransduction in photoreceptors?
Light causes hyperpolarization and activates a G-protein cascade
The process reduces cGMP, closing cation channels.
What is the function of rods in different lighting conditions?
Function in scotopic conditions but saturate in brighter conditions
Rods are adapted for very low light but cannot handle bright light effectively.
What conditions do cones function in?
Photopic (daylight) conditions
Cones are responsible for vision in well-lit environments.
Fill in the blank: The eye is approximately _______ in length.
25mm
