the visual system Flashcards
Accessory structures of the eye
- eyelids
- eyelashes
- eyebrows
- lacrimal apparatus - tears
- extrinsic eye muscles
Extrinsic eye muscles
- superior rectus
- interior rectus
- lateral rectus
- medial rectus
- superior oblique
- inferior rectus
move the eyeball laterally, medially, superior and inferiorly.
layers of the eyeball
- fibrous tunic
- vascular tunic
- retina
fibrous tunic
- the sclera
- the cornea
The sclera
- dense connective tissue
- gives shape and rigidity to the eyeball
- protects inner parts
- provides an attachment point for extrinsic muscles
the function of the cornea
- curved and helps focus light onto the retina.
Vascular tunic - middle layer
- the choroid
- ciliary body
- the iris
the choroid
- the vascular tunic and lines the internal surface of the sclera
- provides nutrients for the retina and absorb stray light
ciliary body
- capillaries that secrete aqueous humour (provide nutrients for the lens and cornea).
ciliary muscle
alters the shape of the lens for near and far vision
the function of the iris?
- between the cornea and the lens
- regulates the amount of light entering the eye through the pupil
bright light = circular muscles contract
dim light = radial muscles contact
Layers of the retina
- The pigmented layer
- The neural layer
the pigmented layer
- between the choroid and neural layer
- prevents reflection and scattering of light within the eyeball
the neural layer
- an outgrowth of the brain
- processes visual information before sending it down the optic nerve.
has 3 cell types - photoreceptors, bipolar cell layer, the ganglion cell layer
It’s layered so that light passes through the ganglion and the bipolar layer before reaching the photoreceptors
Photoreceptors
Rods: allows to see a dim light
Cones: activated during bright light conditions (colour receptors).
pathway of visual information
photoreceptors = bipolar cells = ganglion cells
- axons exit the eyeball through the optic disk and form the optic nerve.
optic disk
no photoreceptors = blind spot
central fovea
- has a small depression on the retina
- contains only cones
- contains bipolar cells and ganglion but doesn’t cover the cones
- highest visual activity
the function of the lens
- helps focus on images onto the retina = accommodation
- far = flatter
- close = round
optic chiasm
axons of the left and right optic nerve pass through it
visual field
- help produce depth perception
- visual fields of both eyes overlap
- light rays from the nasal half of the visual field fall on the temporal the retina
- light rays on the temporal half of the visual field fall on the nasal half of the retina.
pathway of visual information
optic nerve = optic chiasm = optic tract = thalamus = cerebral cortex
