Visual System Flashcards
Retina
Innermost tissues layer and contains light sensitive neurons
Sclera
Outermost layer composed of fibrous white tissue
Cornea
Transparent anterior portion of the sclera
Choroid
Capillary bed that nourishes the retina
Ciliary muscle
Adjust the shape of the lens, changing refractive power
Lens
Transparent
Thickens and flattens (or accommodates) to focus light on retina
How does the lens focus on distant objects?
Lens gets thin and flat
How does the lens focus on near objects?
The lens gets thick and round
Emmetropia
The normal refraction
Light is focused on the retina
Myopia
Lens not flat enough or eye too long
Light focused in front of the retina
Near sided
Hyperopia
Lens not round enough or eye too short
Light focused behind retina
Far sided
Iris
Colored portion of the eye
Contains muscles that adjust pupil size
Pupil
Size changes in response to light
Controlled by sympathetic and parasympathetic innervation
Fovea
Area of highest receptor density and highest visual acuity within the retina
Two types of photoreceptors
Rods - black and white vision
Cones - color vision
Characteristics of rods
Very sensitive to light - respond to single photon
Contain single photopigment
Characteristics of cones
Mediate daylight vision - activation needs many photons
3 types of cones for different wavelengths (blue=short, green=medium, red=long)
Response to light speed
Rods are slow
Cones are fast
Steps of the visual pathway
Optic nerve
Optic tract
Optic radiations
Primary visual cortex
Information from the nasal retina is associated with what
Temporal (lateral) portions of the visual field
What are areas of visual cortex that respond more strongly to visual stimuli presented to one eye called?
Ocular dominance columns
Dorsal visual pathway is concerned with what
Where objects are
Ventral visual pathway cares about what
What objects are
