The eye-vision
Cranial nerve that controls movement of eyeball > lateral rectus muscle (extrinsic eye muscle)
Abducens nerve VI
An alteration in the curvature of the lens to focus an image on the retina
Accomodation
A change in pupillary size in response to changes in light intensity> pupillary muscle contract, they change the diameter of the pupil
Adaptation
Parasympathetic activation in response to bright light causes the pupils to constrict; Sympathetic activation in response to dim light causes the pupils to dialate
Adaptation
Maintains shape and supplies oxygen and nutrients to lens and cornea
Anterior cavity
In-between cornea and iris; contains aqueous humor
Anterior chamber
Contains microscopic ciliary muscles> Oculomotor nerve III: Controls intrinsic eye movement (changes the diameter of lens, adjusting the amount of light entering the eye, and change the shape of the lens to focus images on the retina) Ciliary processes: epithelium covering the ciliary muscles (body)
Ciliary body
function only under conditions of bright light > color receptors
Cones
Optics: The lens focuses the visual image on the retina: "normal" visual acuity (20/20)
Emmetropic
Sharpest image: area of clearest vision; only cones
Fovea centralis
Optics: The image is focused behind the retina Due to a shortened eyeball or a thin lens
Hyperopia (farsighted)
Cranial nerves involved with the eye
II, III, IV, VI
Light from each portion of an object is focused on a different part of the retina; Resulting image arrives upside down and reversed
Image formation
layers:neuroretina, fovea centralis, blind spot, optic nerve
Inner or retinal
"Color of your eye" > pigmented; regulates the smount of light entering the vitreous chamber; pupillary muscles:contract --> change size of pupil
Iris
Transparent, flexible structure held in place by ciliary ligaments; fine tunes focusing of light, refracts (bends) light
Lens
layer: choroid, ciliary body, ciliary processes, lens, iris, pupil
Middle or vascular
Optics: The image is focused anterior of the retina; Due to an elongated eyeball or thickened lens
Myopia (nearsighted)
Contains photoreceptors (rods & cones)
Neuroretina
Converts light into receptor potential and nerve impulses > output to brain via axons of ganglion cells> which form the optic nerve II
Neuroretina
Looks like wet tolet paper
Neuroretina
Cranial nerve that controls the constriction of the pupils and thickening of the lens of the eye (intrinsic eye muscles)
Oculomotor nerve III
Carries visual information: signals from the retina of the eye to the optic chiasm; formed by axons of all the photoreceptors
Optic Nerve II
Also called the "blind spot" > no photoreceptors (light goes unnoticed)
Optic disc
Opening through which axons of the ganglion cells emerge as optic nerve
Optic disc
Site where the optic nerve exits the eyeball (origin of optic nerve)
Optic disc
cranial nerve responsible for vision
Optic nerve II
Light causes a hyperpolarizing receptor potential in photoreceptors, which decreases release of neurotransmitter (glutamate in rods).
Photoreception
Transduction of light into electricle signal occurs in outer segments of photoreceptors
Photoreception
Maintains shape and keeps retina applied to choroid
Posterior cavity
In-between iris and lens;contains aqueous humor
Posterior chamber
Opening in the center of iris through which light enters the eye; "Hole" in the center of iris
Pupil
specialized receptors for dim light > black/grey/white
Rods
Cranial nerve that controls movement of eyeball > superior oblique muscle (extrinsic eye muscle)
Trochlear nerve IV
Contains vitreous humor
Vitreous chamber
ability to focus for close (less than 20 feet) vision
accommodation
fluid filling the anterior segment of the eye
aqueous humor
light-bending media of the eye (4)
aqueous humor, cornea, vitreous humor, lens
blurred vision due to unequal curvatures of the lens or cornea
astigmatism
The plasma membrane in the outer segment of the photoreceptor contains _____ _____ sodium ion (NA+) channels
chemically gated
Vascular, provides blood supply and absorbs scattered light; reflects light (mirror); appears blue only in animals
choroid
forms the bulk of the heavily pigmented vascular layer
choroid
Alters shape of lens for far and near vision; secretes aqueous humor
ciliary body
modification of the choroid that controls the shape of the crystalline lens and contains the ciliary muscle
ciliary body
smooth muscle structures (2)
ciliary body, iris
form (by filtration) the aqueous humor
ciliary processes of the ciliary body
Correction of myopia by use of a ___ lens that diverges entering light rays so that they come into focus directly on the retina
concave
medial movement of the eyes during focusing on close objects
convergence
Correction of hyperopia by use of ---- lens that converges entering light rays so that they focus directly on retina
convex
Clear, non vascular; Admits and refracts (bends) light
cornea
anterior continuation of the sclera--your "window on the world"
cornea
Pathway of light
cornea, pupil, lens, neuroretina, optic nerve, optic chiasm, optic tract, thalamus, primary visual lobe (occipital)
normal vision
emmetropia
Accommodation the lens _____to focus on a distant object (ciliary muscles _____ , lens ______ for distant vision)
flattens, relaxed, flattened
area of critical focusing and discriminatory vision
fovea centralis
inability to focus well on close objects (farsightedness)
hyperopia
nearsightedness
myopia
layer containing the rods and cones
neuroretina
part of the eye that lacks photoreceptors
optic disc
light bending
refraction
Accommodation the lens becomes_____to focus on nearby object (ciliary muscles are _____> lens ____ for close visions)
rounder, contracted, rounded
composed of tough, white, opaque, fibrous connective tissue
sclera
the "white" of the eye (provides shape and protects inner parts, as well as mechanical support, and physical support)
sclera
Outer or supporting layers
sclera and cornea
drains the aqueous humor from the eye
scleral venous sinus
substance occupying the posterior segment of the eyeball
vitreous humor