Ch 15- The Special Senses Flashcards
cards for the 94 slides
five special senses
vision, olfaction, gustation, hearing, equilibrium
most dominant sense
vision, has most sensory receptors
conjuctiva
transpart mucous membrane
conjunctiva function
produces lubricating mucous, preventing dry eye
palpebrae
eyelids, allow open or close.
orbicularis oculi muscle- what is it what does it do
skeletal muscle tissue under eye- allows eye to close
levator palpebrae superioris muscle- what is it what does it do
upper eyelid muscle, allows you to stop eye opening or keep it- pulls eyelid up
lacrimal apparatus
produces and drains tears, also protects.
lysozyme
lubricate for eye surface, washes away foreign bodies in eye and kills bacteria and other pathogens
lacrimal apparatus makeup
lacrimal glands (produce and release tears), lacrimal canaliculi (drains tears at medial portion), nasolacrimal duct(drains tears from cannaliculi into nasal cavity)
extrinsic eye muscle function
allows movement of the eye in orbit, each attach to the sclera of the eye (white)
6 extrinsic eye muscles
superior rectus, inferior rectus, lateral rectus, medial rectus, superior oblique, inferior oblique
lateral rectus
moves eye laterally
medial rectus
moves eye medially
superior rectus
elevates eye, turns medially (up or down)
inferior rectus
depresses eye, turns medially (up or down)
inferior oblique
elevates eye, lateral movement (counteracts direction eye is pulled)
superior oblique
(depresses eye and turns it medially(counteracts direction of eye pull)
what do oblique muscles do
balance out rectus muscles
fibrous layer
outermost coat pf eye, 2 regions
the 2 regions of fibrous layer
sclera and cornea
sclera
white of eye, gives shape and anchor for the muscles
cornea
transparent layer at anterior region, allows light to enter, bends the light. Has pain receptors, regenerates fast, no blood vessels with no immune system
vascular layer
middle coat with 3 regions
3 vascular layer regions
choroid, cilliary body, iris
choroid
well vascularized layer, absorbed light with dark color, allows easy brain interpretation bc no scattering
cilliary body
cilliary muscle (controls lens shape) cilliary processes (secretes aqueous humor), suspensory ligaments (holds lens in place and emits tension from ciliary muscle to lens)
iris
controls the melanin, colored portion of eye, has sphincter pupillae and dilator pupillae
pupil
central opening, allows light to enter eyeball
sphincter pupillae
bright light, pupil decreases in size bc layer thickens
dilator pupillae
dim light, pupil increases in size bc layer narrows
retina
innermost eye layer, has the photoreceptors, responds to light and color. has pigmented layer and neural layer.
pigmented layer of retina
superficial layer, absorbs light, stores vitamin A, makes it so you can produce and regenerate the photoreceptors.
neural layer
deepest layer, generates AP to brain, has photoreceptor cells, rods and cones plus bipolar and ganglion cells
rods
dim light and peripheral visio, outer retina layers
cones
bright light, allows color vision. in fovea central’s ands macula lutea,it is less sensitive to light
bipolar and ganglion cells
generate AP to light stimuli
optic disc
blind spot, no photoreceptors, Brain fills in missing gaps and its in back of eye
macula lutea and fovea centralis
macula: only cones, photoreceptors receive direct light and pushes to side when light strikes cones, ACUTE vision here
fovea: center of macula, 1/1000th of visual field
lens
transparent and flexible structure, has lens fibers for thickness, disadvantage over time bc lens fibers build up and makes it harder to change shape so vision loss occurs
anterior segment
aqueous humor, supplies nutrioents and O2 to structures and removes waste washes it away, it is constantly drained and produced (rate of this must be equal)
glaucoma
too much aqueous humor produced
posterior segment
vitreous humor, behind lens, lasts a lifetime, contributes to pressure on eye and holds retina in place as well as transmits light
visible light spectrum
400-700 nm, light strikes object bounces off it and then strikes the eye. the color of object is what waves are absorbed and what is reflected. WHITE is reflected BLACK is absorbed
light refraction
bending of light as it passes from one substance to another with different density
speed through light mediums
faster transmission in air, slower in solid. light travels ay constant speed thru single medium, refraction is important for vision bc air travel to cornea then must be able to reflect light for stimulation of the photoreceptors
lens and cornea and focusing light
cornea will bend the light, but won’t change shape. lens changes shape to fine tune the refraction- less power is less bulge, more power is more bulging.
relaxation of cilliary muscles
increased tension in suspensory ligaments, pulled tight, so the lens flattens and bends less light, less refractory power
contraction of cilliary muscles
decreased tension in suspensory ligaments, go slack, lens bulges, high refectory power and bends light very well.
looking at an objet far away…
lens flattens, less refractory power
far point of vision
point where lens doesn’t need to change shape to focus, 20+cfeet, distant object means light entering rays are parallel so it can bend easily to focus in on retinal
lens accommodation
ciliary muscles contract, lens will bulge when object is up close, must be rounded
pupil constriction
don’t want scattering here would confuse visual signal, smaller diameter to tell how much light goes in, prevents the diverging rays from entering eye
convergence of eyes
closer object means more conversion, keeps object focused on foveae (highest resolution) and medial rotation
near point of vision
4inches, but increases with age we lose ability to focus close to face, these light rays are more divergent as they enterr the eye, more divergent light rays striking retina means brain is confused so we want less divergence when near
phoptorecepots, rods and cones
very modified and dif from other neurons, outer segment has folded photopigments into discs which respond to light stimuli.(actual response to light AP generated) inner has embedded in neural layer of retina, metabolic processes of them with connection to outer cell body segment.