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260 Cards in this Set
- Front
- Back
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Eyes can sense _______ gradations of light
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10,000,000
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Eyes can sense ________ shades of color
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7,000,000
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Eyes are responsible for about ?
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75% of all that we perceive
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the only place we can see the CNS without surgery and the only place where the CNS is in direct contact with the outside world.
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The eyes
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Four Accessory structures for the eyes
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Eyebrows, eyelids, eyelashes, tear glands
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Eyes respond to light and initiate
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afferent action potentials
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Eyelids or palpebrae
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protect & lubricate the eyes
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Tarsal glands produce
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oily secretions keep lids from sticking together
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Two types of Conjunctiva
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palpebral & bulbar
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Eyeball =
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1 inch in diameter
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5/6 of Eyeball inside?
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orbit
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Eyelashes & eyebrows help protect from?
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foreign objects, perspiration & sunlight
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Sebaceous glands are found at base of?
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eyelashes (infection = sty)
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Palpebral fissure is gap between ?
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the eyelids
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About 1 ml of tears produced ?
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per day
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Spread over eye by ?
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blinking
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Tears contain bactericidal enzyme called ?
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lysozyme.
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Extraocular Muscles?
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Six muscles that insert on the exterior surface of the eyeball
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Extraocular Muscles have the smallest motor units of ?
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any skeletal muscle
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for precision and smoothness of motion Extraocular Muscles have how many fibers per nuron?
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2-3 ms fibers/neuron
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What three Nerves innervate the Extraocular Muscles?
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CN III (oculomotor), IV (trochlear) and VI (abducens)
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What are the 4 rectus muscles of the Extraocular Muscles?
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superior, inferior, lateral and medial
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What are the 2 oblique muscles of the Extraocular Muscles?
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inferior and superior
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Three coats or tunics of the eye?
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Vascular, Fibrous and Nervous
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Fibrous?
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Consists of sclera and cornea
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Vascular?
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Consists of choroid, ciliary body, iris
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Nervous?
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Consists of retina
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Sclera?
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White outer layer, maintains shape, protects internal structures, provides muscle attachment point, continuous with cornea
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Cornea?
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Avascular, transparent, allows light to enter eye and bends and refracts light
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Iris?
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Controls light entering pupil; smooth muscle
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Ciliary muscles?
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Control lens shape; smooth muscle
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Retina contains?
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neurons sensitive to light
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Macula lutea or fovea centralis?
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Area of greatest visual acuity
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Optic disc?
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Blind spot
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Anterior Compartment?
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Aqueous humor
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Posterior Compartment?
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Vitreous humor
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Lens Held by?
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suspensory ligaments attached to ciliary muscles
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Describe the lens?
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Transparent, biconvex
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Fibrous Tunic: Layer?
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outer layer
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Vascular Tunic: Layer?
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middle layer
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Nervous Tunic: Layer?
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inner layer
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Cornea Helps focus ?
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light
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3 layers of cornea
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-nonkeratinized stratified squamous
-collagen fibers & fibroblasts -simple squamous epithelium |
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A transplanted Cornea has no blood vessels so no ?
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antibodies to cause rejection
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Cornea is Nourished by ?
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tears & aqueous humor
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Description of Sclera?
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white of the eye
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Sclera provides?
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shape & support
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At the junction of the sclera and cornea is an opening ?
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scleral venous sinus
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The sclera is posteriorly pierced by
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Optic Nerve (CN II)
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Choroid?
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pigmented epithilial cells (melanocytes) & blood vessels
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Choroid provides?
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nutrients to retina
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black pigment in melanocytes absorb?
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scattered light
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ciliary processes do (2)?
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-folds on ciliary body
-secrete aqueous humor |
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ciliary muscle is?
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smooth muscle that alters shape of lens
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Iris?
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Colored portion of eye
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Hole in center of iris is ?
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pupil
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circular muscle fibers contract in bright light to ?
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shrink pupil
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radial muscle fibers contract in dim light to ?
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enlarge pupil
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Parasympathetic stimulation constricts?
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pupils
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sympathetic – dilates the?
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pupils
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Constrictor pupillae (circular) are innervated by ?
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parasympathetic fibers
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Dilator pupillae (radial) are innervated by?
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sympathetic fibers.
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Is the lens avascular?
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yes
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In the lens Crystallin proteins arranged in ?
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layers
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Lens held in place by ?
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yes
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The lens Focuses light on ?
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fovea
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Suspensory ligaments attach lens to ?
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ciliary process
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Ciliary muscle controls tension on ?
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ligaments & lens
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Retina is located?
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Posterior 3/4 of eyeball
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In the Optic disc the optic nerve exits ?
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the back of eyeball
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Anterior cavity filled with ?
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aqueous humor
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Anterior cavity filled with aqueous humor produced by ?
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ciliary body
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aqueous humor replaced every ?
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90 minutes
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2 chambers of aqueous humor?
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anterior and posterior
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anterior chamber between
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cornea and iris
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posterior chamber between
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iris and lens
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Posterior cavity filled with ?
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vitreous body (jellylike)
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Posterior cavity formed once during ?
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embryonic life
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Aqueous Humor Continuously produced by ?
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ciliary body
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Aqueous Humor Flows from posterior chamber into anterior through the ?
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pupil
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Scleral venous sinus AKA?
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canal of Schlemm
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opening in white of eye at junction of cornea & sclera ?
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Scleral venous sinus
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Scleral venous sinus drains aqueous humor from eye to ?
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bloodstream
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Glaucoma?
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increased intraocular pressure that could produce blindness caused by a problem with drainage of aqueous humor
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Eye functions like a ?
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camera
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Iris allows light into ?
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eye
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Lens, cornea, humors focus light onto ?
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Retina
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Light striking retina is converted into ?
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action potentials relayed to brain
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Visible light?
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Portion of electromagnetic spectrum detected by human eye
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Refraction?
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bending of light
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Divergence?
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Light striking a concave surface
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Convergence?
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Light striking a convex surface
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Focal point?
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Point where light rays converge and cross
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Definition of Refraction = Bending of light as it passes from ?
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one substance (air) into a 2nd substance with a different density (cornea)
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In the eye, light is refracted by ?
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the anterior & posterior surfaces of the cornea and the lens
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Major Processes of Image Formation?
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-Refraction of light
-Accommodation of the lens -Constriction of the pupil |
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Image focused on retina is?
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inverted & reversed from left to right
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75% of refraction is done by?
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cornea - rest is done by the lens
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Light rays from > 20’ are nearly parallel and only need to ?
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be bent enough to focus on retina
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Light rays from < 6’ are more divergent & need ?
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more refraction
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extra process needed to get additional bending of light is called ?
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accommodation
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Convex lens refract light rays towards ?
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each other
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Lens of eye is convex on ?
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both surfaces
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To View a distant object the lens is nearly flat by pulling of ?
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suspensory ligaments
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To View a close object the ciliary muscle is contracted & decreases the ?
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pull of the suspensory ligaments on the lens
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elastic lens thickens as the tension is?
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removed from it
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increase in curvature of lens is called ?
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accommodation
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Emmetropia?
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Normal resting condition of lens
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Far vision?
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20 feet or more from eye
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Near vision?
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closer than 20 feet
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Near point is the?
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closest distance from the eye an object can be in clear focus
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Near point in a young adult?
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4 inches
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Near point in a 40 year old?
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8 inches
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Near point in a 60 to 80 year old?
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31 inches
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glasses replace refraction previously provided by/
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increased curvature of the relaxed, youthful lens
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Emmetropic eye ?
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-normal
-can refract light from 20 ft away |
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Myopia?
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-nearsighted
-eyeball is too long from front to back -glasses concave |
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Hypermyopia?
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-farsighted
-eyeball is too short -glasses convex |
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Astigmatism?
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-corneal surface wavy
-parts of image out of focus |
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Constriction of the Pupil?
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-Narrows beam of light that enters the eye
-Prevents light rays from entering the eye through the edge of the lens -Sharpens vision by preventing blurry edges -Protects retina from very excessively bright light |
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Convergence of the Eyes?
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As you look at an object close to your face, both eyeballs must turn inward
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Binocular vision in humans has both eyes ?
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looking at the same object
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Convergence is required so that light rays from the object will ?
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strike both retinas at the same relative point
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For Convergence extrinsic eye muscles must ?
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coordinate this action
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Retina Provides black backdrop for ?
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increasing visual acuity
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Rods?
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Noncolor vision
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Cones
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Color vision
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Rhodopsin reduction?
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Light adaptation
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Rhodopsin production
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Dark adaptation
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Retina’s 3 layers of neurons ?
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-photoreceptor layer
-bipolar neuron layer -ganglion neuron layer |
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Pigmented epithelium (nonvisual portion) absorbs?
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stray light & helps keep image clear
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Retina’s 2 other cell types (modify the signal)?
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-horizontal cells
-amacrine cells |
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Summary of Rods (5)?
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-rod shaped
-shades of gray in dim light -120 million rod cells -discriminates shapes & movements -distributed along periphery |
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Summary of Cones (3)?
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-cone shaped
-sharp, color vision -6 million |
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Summary of fovea of macula lutea (4)?
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-densely packed region
-at exact visual axis of eye -2nd cells do not cover cones -sharpest resolution or acuity |
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Rods & cones transduce light into?
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action potentials
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Rods & cones excite ?
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bipolar cells
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Bipolars excite ?
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ganglion cells
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Axons of ganglion cells form ?
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optic nerve leaving the eyeball (blind spot)
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The nerves from the retina go to ?
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the thalamus & then the primary visual cortex
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Photoreceptors are named for?
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shape of outer segment
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Transduction of light energy into a receptor potential in?
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outer segment
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integral membrane protein of outer segment membrane ?
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Photopigment
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Photopigments = ?
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opsin (protein) + retinal (derivative of vitamin A)
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rods contain ?
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rhodopsin
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cone photopigments contain 3 different opsin proteins permitting?
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the absorption of 3 different wavelengths (colors) of light
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Isomerization?
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light cause cis-retinal to straighten & become trans-retinal shape
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Photopigment Bleaching (2)?
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-enzymes separate the trans-retinal from the opsin
-colorless final products |
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Regeneration? (resynthesis of a photopigment)
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in darkness, an enzyme converts trans-retinal back to cis-retinal
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Formation of Receptor Potentials In darkness: Na+ channels are held open and photoreceptor is?
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always partially depolarized (-30mV)
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Formation of Receptor Potentials In darkness:
continuous release of ? |
inhibitory neurotransmitter onto bipolar cells
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Formation of Receptor Potentials In light: release of inhibitory neurotransmitter is ?
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stopped
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Formation of Receptor Potentials In light: bipolar cells become excited and?
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a nerve impulse will travel towards the brain
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Formation of Receptor Potentials In light:
enzymes cause the closing of Na+ channels producing ? |
a hyperpolarized receptor potential (-70mV)
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Pigment epithelium near the photoreceptors contains large amounts of ?
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vitamin A and helps the regeneration process
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After complete bleaching, it takes 5 minutes to regenerate 1/2 of the rhodopsin but only 90 seconds to ?
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regenerate the cone photopigments
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Full regeneration of bleached rhodopsin takes ?
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30 to 40 minutes
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Rods contribute little to daylight vision, since ?
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they are bleached as fast as they regenerate.
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Color blindness?
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inability to distinguish between certain colors
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red-green color blind person can not tell
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red from green
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nyctalopia ?
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Night blindness
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Night blindness (2)?
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-difficulty seeing in low light
-inability to make normal amount of rhodopsin |
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Light adaptation?
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adjustments when emerge from the dark into the light
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Dark adaptation?
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adjustments when enter a dark from a bright situation
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light sensitivity increases as ?
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photopigments regenerate
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during first 8 minutes of dark adaptation, only cone pigments are regenerated, so ?
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threshold burst of light is seen as color
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after sufficient time, sensitivity will increase so that a flash of a single photon of light will be seen as ?
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gray-white
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Transmission of most signals occur in the retinal neurons by ?
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electrotonic conduction (not action potentials).
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The only retinal neurons that fire action potentials are the ?
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ganglion cells.
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Electrotonic conduction ?
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cytoplasmic spreading of direct current (hyperpolarization) from site of generation (outer segments) all the way to site of release of synaptic vesicle without abatement
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The significance of electrotonic conduction is that it allows for ?
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graded conduction of signal strength by rods and cones
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one cone cell synapses onto one bipolar cell produces ?
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best visual acuity
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600 rod cells synapse on single bipolar cell increasing ?
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light sensitivity although slightly blurry image results
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126 million photoreceptors converge on
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1 million ganglion cells
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horizontal cells enhance contrasts in visual scene by ?
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lateral inhibition of bipolar cells in the area
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amacrine cells excite bipolar cells if ?
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levels of illumination change
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Lateral inhibition – provides ?
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contrast detection and enhancement
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signals transmitted directly from photoreceptors to bipolar cells are ?
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excitatory
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signals transmitted laterally (via horizontal cells) are always
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inhibitory
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Left occipital lobe receives visual images from?
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right side of an object through impulses from nasal 1/2 of the right eye and temporal 1/2 of the left eye
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Left occipital lobe sees
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right 1/2 of the world
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Fibers from nasal 1/2 of each retina cross?
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in optic chiasm
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Visual information in optic nerve travels to occipital lobe for ?
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vision
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Visual information in optic nerve travels to midbrain for ?
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controlling pupil size & coordination of head and eye movements
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Visual information in optic nerve travels to hypothalamus to ?
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establish sleep patterns based upon circadian rhythms of light and darkness
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Determination of distance (3)?
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-Sizes of retinal images of known objects
-Moving paralax – monocular; relative distance of different objects -Binocular paralax (strereopsis) |
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strereopsis
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Binocular paralax
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Myopia?
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Nearsightedness
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Hyperopia?
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Farsightedness
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Presbyopia?
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Degeneration of accommodation, corrected by reading glasses
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Astigmatism?
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Cornea or lens not uniformly curved
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Strabismus?
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Lack of parallelism of light paths through eyes
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Retinal detachment?
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Can result in complete blindness
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Glaucoma?
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Increased intraocular pressure by aqueous humor buildup
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Cataract?
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Clouding of lens
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Macular degeneration?
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Common in older people, loss in acute vision
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Diabetes?
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Dysfunction of peripheral circulation
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The Special Senses?
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Smell, taste, vision, hearing and equilibrium
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Ophthalmology is science of the ?
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eye
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Otolaryngology is science of the?
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ear
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Chemical Senses?
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Interaction of molecules with receptor cells
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Olfaction?
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smell
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gustation?
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taste
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Olfaction (smell) and gustation (taste) both project to ?
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cerebral cortex & limbic system
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Olfactory Epithelium: 1 square inch of membrane holding?
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10-100 million receptors
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Olfactory Epithelium: Covers ?
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superior nasal cavity and cribriform plate
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Olfactory Epithelium - 3 types of cells: ?
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olfactory receptors, supporting cells and basal stem cells
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Odor producing molecules are small (3/4 - 18/20) atoms with ?
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relatively high water and lipid solubility
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Olfactory receptors?
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bipolar neurons with cilia or olfactory hairs
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Supporting cells of the Olfactory Membrane ?
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columnar epithelium, provide physical support, nourishment, electrical insulation, and detoxification
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Basal cells = ?
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stem cells
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Olfactory (Bowman’s) glands produce ?
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mucus, dissolve odorants
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Both epithelium & glands are innervated by?
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cranial nerve VII.
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Sence of smell : Odorants bind to ?
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receptors
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Lipophylic odorants may use ?
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ODP (odorant-binding proteins) in mucous
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Activated receptors are coupled to?
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G proteins which activate 2nd messengers (cAMP, phospholipase C)
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Adaptation = ?
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decreasing sensitivity
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Olfactory adaptation is ?
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rapid – sometimes beneficial
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Olfactory adaptation : 50% in 1 second, complete in ?
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1 minute
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Olfaction discrimination – over ?
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10,000 odors can be distinguished
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Differentiation of stimulus intensity is poor ?
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30% change needed to be detected
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Axons from olfactory receptors form the?
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olfactory nerves (CN I) that synapse in the olfactory bulb
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olfactory bulb is part of ?
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telencephalon (the only sense which has 1st synapse in telencephalon)
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Axons pass through ?
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40 foramina in cribriform plate
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Second-order neurons within the olfactory bulb form the ?
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olfactory tract that synapses on primary olfactory area of temporal lobe
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Other pathways lead to the frontal lobe (Brodmann area 11) where identification of ?
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the odor occurs
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memory and emotional responses to smell happen where?
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hypothalamus and the limbic system
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There are about 1,000 different olfactory receptors, yet we can distinguish ?
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10,000 different odors
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different patterns of activation of olfactory glomeruli allow us to?
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distinguish odors
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role of location (on top of nasal concha) and current eddies?
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Sniffing
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naked endings of trigeminal nerves are stimulated by irritating substances, e.g menthol, chlorine… ?
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Pain receptors in nose
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These endings are also responsible for initiating sneezing, lacrimation, respiratory inhibition
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Pain receptors in nose
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perception of odor in the form of pheromones: role in reproduction and ingestion; has ~ 30 serpentine receptors that differ from the olfactory receptors called ?
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Vomeronasal organ
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Anosmia?
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associated with hypogonadism (Kallmann’s syndrome),
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hyposmia?
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can be age associated
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dysosmia?
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Age related increase in olfactory threshold
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Taste detected by?
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taste buds
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Vallate?
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100-300 buds
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Fungiform?
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over entire tongue
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Foliate?
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only in childhood
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Filiform?
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only tactile, no taste
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Receptors on hairs detect ?
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dissolved substances
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Taste types (5 modalities)?
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-Sour – H+
-Salty – Na+ -Bitter – cations: Mg, Ca, ammonium, urea, caffeine, nicotine, morphine (no common feature) -Sweet – organic substances, 3-D structure is important -Umami |
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Taste requires dissolving of ?
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substances
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10,000 taste buds found on ?
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tongue, soft palate & larynx
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3 cell types of taste: ?
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supporting, receptor & basal cells
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Anatomy of Taste Buds?
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An oval body consisting of 50 receptor cells surrounded by supporting cells
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Basal cells develop into supporting and then ?
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into new receptor cells
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Receptor cells have life span of?
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10 days
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Taste threshold ?
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varies with stimuli
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Intensity discrimination ?
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30%
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Abnormalities?
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ageusia, hypogeusia, disgeusia; temporary, permanent
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First-order gustatory fibers found in ?
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cranial nerves
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VII (facial) serves?
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anterior 2/3 of tongue
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IX (glossopharyngeal) serves ?
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posterior 1/3 of tongue
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X (vagus) serves ?
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palate & epiglottis
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Signals travel to the?
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medulla
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Signals travel from the medulla to?
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the thalamus or limbic system (strong association with emotions) & hypothalamus
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limbic system ?
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strong association with emotions
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Taste fibers extend from the thalamus to the ?
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primary gustatory area on parietal lobe of the cerebral cortex
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