The Eye and Vision Flashcards
A sensory organ that has three layers, a lens, and humors.
Eye
Includes eyebrows, eyelids, conjunctiva, lacrimal apparatus, and extrinsic eye muscles.
Accessory Structures
Six muscles that control the movement of the eyeball.
Extrinsic Eye Muscles
Moves eye laterally
Lateral Rectus m.
Moves eye medially
Medial Rectus m.
Elevates eye and turns it medially
Superior Rectus m.
Depresses the eye and turns it medially.
Inferior Rectus m.
Elevates the eye and turns it laterally
Inferior Oblique m.
Depresses the eye and turns it laterally
Superior Oblique m.
The outermost coat of the eyeball.
Fibrous Tunic
The posterior portion and bulk of the fibrous tunic. White and opaque in color. Protects the eye and provides anchoring sites for the extrinsic muscles.
Sclera
The anterior of the fibrous tunic. Translucent. Allows light to enter the eye.
Cornea
The middle coat of the eyeball.
Vascular Tunic
A blood vessel-rich, dark brown membrane that forms the posterior 5/6s of the vascular tunic. Provides nutrients to all layers of the eye and helps absorb light.
Choroid
Ring of tissue that encircles the lens. Contains smooth muscle that controls the lens shape and secretes fluid into the anterior segment.
Ciliary Body
The colored part of the eye. Made up of two smooth muscle layers that vary pupil size.
Iris
The central opening that allows light to enter the eye.
Pupil
The innermost layer of the eye. Contains photoreceptors and neurons involved in processing responses to light.
Retina
A single-cell-thick lining next to the choroid. Absorbs light and prevents it from scattering in the eye.
Pigmented Layer of the Retina
The transparent inner layer of the retina. Contains neurons.
Neural Layer of the Retina
Produce signals in response to light.
Photoreceptors
Cells where action potentials are generated in the retina.
Bipolar cells
Leave the posterior aspect of the eye as the optic nerve.
Ganglion Cells
Location where the optic nerve exits the eye. Lacks photoreceptors.
Optic Disc
Dim-light and peripheral vision receptors. Most numerous and most light sensitive type of photoreceptor.
Rods
Vision receptors for bright light and provide high-resolution color vision.
Cones
Contains mostly cones. Lateral to the blind spot of each eye.
Macula lutea
Area where retinal structures are displaced. Contains only cones.
Fovea Centralis
Area behind the lens. Filled with vitreous humor.
Posterior Segment
Fluid in the posterior chamber. Transmits light, supports the posterior surface of the lens and holds the neural layer of the retina firmly against the pigmented layer, contributes to intraocular pressure, helping to counteract the pulling force of the extrinsic eye muscles.
Vitreous Humor
Area in front of the lens. Filled with aqueous humor.
Anterior Segment
A clear fluid that is similar to plasma. Supplies nutrients and oxygen to the lens, cornea, some cells of the retina, and it carries away metabolic wastes.
Aqueous Humor
Venous canal where aqueous humor drains.
Scleral Venous Sinus
A transparent, flexible structure that can change shape to precisely focus light on the retina.
Crystalline Lens
Found on the anterior lens surface. Consists of cuboidal cells.
Lens Epithelium
Cells that form the bulk of the lens. Contain no nuclei and few organelles.
Lens Fibers
Precisely folded proteins that form the body of the lens.
Crystallins
Includes all energy waves.
Electromagnetic Radiation
The part of the electromagnetic spectrum that our eyes respond to.
Visible Spectrum
Changes in light speed that occur when light passes through another medium with a different density.
Refraction
Location where light rays converge.
Focal Point
The image formed by a convex lens.
Real Image
The distance beyond which no change in lens shape is needed for focusing.
Far Point of Vision
The normal eye.
Emmetropic
The nearsighted eye. The focal point is in front of the retina.
Myopic
The farsighted eye. The focal point is behind the retina.
Hyperopic
Process that increases the refractory power of the lens. Caused by contracting the ciliary body and bulging of the lens.
Accommodation
The closest point on which one can focus clearly. Occurs at the maximum bulge the lens can achieve.
Near Point of Vision
Occurs when the size of the pupil is reduced to focus vision.
Constriction
Medial rotation of the eye by constriction of the medial rectus muscle to turn the eye towards the object being view.
Convergence
Change shape as they absorb light.
Visual Pigments (Photopigments)
A light-absorbing molecule made from vitamin A.
Retinal
Proteins that bind to retinal to form visual pigments.
Opsins
Isomer of retinal that is bound to opsin.
11-cis-retinal
Isomer of retinal after a photon has been absorbed. Activates opsin.
All-trans-retinal
Process by which light energy is converted into a graded receptor potential.
Phototransduction
The visual pigment of rods.
Rhodopsin
The breakdown of rhodopsin into retinal and opsin.
Bleaching of the pigment
A G protein activated by light-activated rhodopsin.
Transducin
Binds to cation channels in photoreceptor cells in the dark, holding them open. Broken down by enzyme activated by transducin.
Cyclic GMP (cGMP)
Occurs when moving from darkness into bright light. Rods and cones are strongly stimulated, and large amounts of visual pigments are break down almost instantaneously, producing a flood of signals.
Light Adaptation
Occurs when moving from a well-lit room to a dark one.
Dark Adaption
Where axons of retinal ganglion cells exit the eye.
Optic Nerve
Location where fibers from the medial aspect of the eye cross over to the opposite side.
Optic Chiasma
Contains fibers from the lateral aspect of the eye and fibers from the medial aspect of the opposite eye. Carries all information from the same half of the visual field.
Optic Tracts
Synapse with optic tracts in the thalamus.
Lateral Geniculate Nuclei
Fibers in the cerebral white matter that project to the primary visual cortex.
Optic Radiation
Part of the occipital lobe where conscious perception of visual images occurs.
Primary Visual Cortex
Visual reflex centers in the midbrain that control the extrinsic muscles of the eye.
Superior Colliculi
Part of the hypothalamus that functions as a timer for daily biorhythms.
Suprachiasmatic Nucleus
Three-dimensional vision created because each eye sees a slightly different field.
Depth Perception