unit 8 Flashcards
accessory eye structures
extrinsic eye muscles
eyelids
conjunctiva
lacrimal apparatus
extrinsic eye muscles
six muscles attached to outer surface of eye and produce eye movements
eyelids
eyelashes; tarsal glands produce oily secretions to lubricate eye; ciliary gland between eyelashes
conjunctiva
mucus membrane around eye that secretes mucus to lubricate eye
lacrimal apparatus
lacrimal gland produces tears that drain to lacrimal canaliculi -> lacrimal sacs -> nasolacrimal duct -> nasal cavity
3 layers of eye
fibrous, vascular, sensory
fibrous layer
outside; sclera and cornea
vascular layer
middle; choroid (blood vessels)
sensory layer
inside; retina; outer pigmented layer absorbs light (bipolar neuron); inner neural layer contains the photoreceptors
rods
edges of retina; vision in dim light and peripheral vision (corners); all perception of gray tones
cones
detailed color vision; densest in center of retina; fovea centralis; 3 types that are sensitive to different wavelengths of visible light (blue, green and red)
special senses
smell, taste, sight, hearing, and equilibrium (balance)
percentage of sensory receptors in eyes
70%
humors
fluid that fills interior of eyeball
lens
divides eye into 2 chambers; aqueous humor and vitreous humor; held in place by a suspensory ligament attached to the
ciliary body
anterior chamber
aqueous humor; watery; Helps maintain intraocular pressure and Provides nutrients for the lens and cornea; Reabsorbed into venous blood through the scleral venous sinus, or canal of Schlemm
posterior chamber
vitreous humor; jelly like; Prevents the eye from collapsing and Helps maintain intraocular pressure; holds retina in place
choroid
blood-rich nutritive layer that contains a pigment; prevents light from scattering
ciliary body
iris; moves muscles of eye
iris
smooth muscle; regulates amount of light entering eye
pupil
opening of eye
tapetum lucidum
reflective part in eye for seeing in dark
fovea centralis
lateral to blind spots; only cones; visual acuity (sharpest vision)
blind spots
no photoreceptors
cataract
lens becomes hardened and cloudy
glycoma (glaucoma)
aqueous fluid doesn’t drain; pressure
pathway of light
-light must be focused on a point on retina (fovea centralis)
-light is bent by cornea, lens, humors then retina
-eye is set or distance (over 20ft)
-accommodation
-image is formed
how image forms
-cornea and humors (curve and fluid bend light)
-lens (flat-distant and convex-near vision)
-ciliary body muscle (attached to lens contracting)
-real image (reversed from left to right, upside down, and smaller than object
accommodation
lens must change shape to focus on closer objects
astigmatism
images are blurry; light focusing as lines and not points; unequal curvature of cornea or lens
emmetropia
eyes focus images correctly on retina
hyperopia
convex; farsightedness; near is blurry; eyeball is short from lazy lens; focused behind retina
myopia
concave; nearsightedness; far away is blurry; eyeball is too long-light fails to reach retina; focused in front of retina
refraction
bending light; curve and fluid bend light
convergence
reflexive movement of eyes medially when we focus on a close subject
photo pupillary reflex
bright light causes pupils to constrict (iris - smooth muscles)
accommodation pupillary reflex
viewing close objects causes pupil to constrict
external ear
-auricle (pinna)
-external acoustic meatus (auditory canal)
-tympanic membrane
-only collecting sound waves
middle ear
-tympanic cavity between tympanic membrane, oval window, and round window
-only senses of hearing
-pharyngotympanic tube (auditory tube): equalizes pressure
-3 bones: transmits vibrations to inner ear
internal ear
-sense organs for hearing and balance
-bony labyrinth (cochlea, vestibule, semicircular canals) with perilymph fluid
static equilibrium
(vestibule and maculae) not moving or changing; head is moving and body is still
-vestibular nerve travels to pons and cerebellum to maintain balance
dynamic equilibrium
(crista ampullaris) head and body moving through space or separate movements
maculae
helps keep head erect; reports position of head; otoliths (tiny stones)
crista ampullaris
responds to angular or rotational movements of head; semicircular canals
spiral organ of corti
in cochlear duct; cochlear nerve to auditory cortex on temporal lobe (transmits nerve impulses); sound waves coming and going
sensorineural deafness
damage to nervous system structures involving hearing
conductive deafness
when transmission of sound vibrations through external and middle ears are hindered
olfactory receptors
roof of nasal cavity; olfactory receptor cells (neurons) (nerve to cortex); interprets smells; bipolar neurons
taste receptors
tongue, soft palate, superior part of pharynx, and cheeks; papillae contains receptors; gustatory hairs = stimulated by salvia
5 basic taste sensations
sweet
sour
bitter
salty
umami
vision changes
infants have poor vision and lack color vision and depth perception; will continue to grow and mature; presbyopia: lens elasticity decreases-difficulty focusing on close vision
hearing changes
infants can’t hear; toddlers will start imitating sounds; sensorineural deafness; presbycosis: (otosclerosis) ear bones fuse
taste and smell changes
acute at birth and decrease in sensitivity as older; damage hair; anosmia
optic nerve
Bundle of axons that exit the back of the eye carrying impulses from the retina
optic chiasma
-where the optic nerves cross
-Fibers from the medial side of each eye cross over to the opposite side of the brain
-fibers from the lateral side of each eye stay on same side of brain
Optic tracts
Contain fibers from the lateral side of the eye on the same side and the medial side of the opposite eye; Synapse with neurons in the thalamus
Optic radiation
Axons from the thalamus run to the occipital lobe; Synapse with cortical cells, and vision interpretation (seeing) occurs
what does the ear house
hearing and equilibrium senses
chemoreceptors
receptors; smell and taste
oval window
sound enters
round window
excess sound pressure exits
high pitched noise
receptor cells are close to oval window;; short and snap off
low pitched noise
specific hair cells that are further along cochlea are affected; longer and floppy
3 nerves for taste
-Facial nerve (cranial nerve VII)
-Glossopharyngeal nerve (cranial nerve IX)
-Vagus nerve (cranial nerve X)
special sense receptors
-Large, complex sensory organs
-Localized clusters of receptors
lateral rectus
outside; move eye laterally (abducens VI)
medial rectus
internal; move eye medially
superior rectus
elevates eye and turns medially
inferior rectus
depresses eye and turns medially
inferior oblique
elevates eye and turns laterally
superior oblique
hooks into trochlea; depresses eye and turns laterally (trochlear IV)
visual acuity
farsighted
mechanoreceptors
receptors for hearing and balance
cupula
gelatinous cap that covers tufts of hair in semicircular canals/crista ampullaris
basilar membrane
contains hair receptors in spiral organ of corti
tectorial membrane
gel-like; capable of bending hair
cells in spiral organ of corti
