visual system

layers of eye

fibrous tunic

vascular tunic (uvea)

nervous tunic

fibrous tunic

sclera, cornea

vascular tunic (uvea)

ciliary body, iris, choroid

nervous tunic

retina, pigmented epithelium

conjuctiva

connective tissue holding eye in place

lacrimal glands

produce tears

nasolacrimal duct

drains tears from eye to nasal cavity

sclera

tough, white, protective outer layer of eye

cornea

dome-shaped; focuses light

pupil

aperture through which light enters eye

dilated pupil

more light enters eye, light scatters more; blurry image

constricted pupil

less light enters eye; less scattering; clearer image

iris

adjusts size of pupil

radial smooth muscle

dilation

circular smooth muscle

constriction

lens

accommodation: adjusts focus of light

rounded lens

light from nearby objects focused onto retina

flat lens

light from distant objects focused onto retina

ciliary body

forms ring

ciliary body: ring

adjusts shape of lens

suspensory ligaments

anchor lens to ciliary body

aqueous humor

watery; produced by ciliary body

delivers oxygen and nutrients to cornea and lens

vitreous humor

gelatinous; provide shape and support for eye

where are photoreceptors located?

retina

photoreceptors: structure

synaptic terminal, inner segment, outer segment (produces pigment)

rods, cones

photoreceptors: flow of information 

photoreceptors → bipolar cells → ganglion cells

• axons of ganglion cells converge to form optic nerve

2 types of photoreceptors

rods

cones

rods: opsin

rhodopsin - pigment

rods: vision

monochromatic vision (grayscale)

rods: vision in light levels and sensitivity

vision in low light levels

high sensitivity

rods: acuity vision and resolution

low acuity vision

low resolution

cones: opsin

multiple opsins; different cone cells with different opsins

cones: vision

color vision

cones: type of vision and sensitivity

daytime vision

low sensitivity

cone: acuity vision and resolution

high acuity vision

high resolution

peripheral retina

peripheral field of vision

peripheral retina: primarily rods or cones?

primarily rods: high sensitivity; low resolution

central retina

central field of vision

central retina: primarily rods or cones?

primarily cones: high resolution; low sensitivity

macula lutea

central retina; high cone density; no large blood vessels

fovea centralis

within macula; especially high cone density

saccades

rapid eye movements, direct fovea to different parts of object

optic disk

point at which optic nerve connects to eye; no photoreceptors

pigmented epithelium

absorbs light; support functions for photoreceptors

choroid

layer of blood vessels behind pigmented epithelium

eyes: side of head

wide field of vision; limited stereoscopic (3D) vision

eyes: front of head

narrower field of vision; increased stereoscopic (3D) vision