Sense Organs Flashcards
Hearing
-mechanical sense
-converts vibrations or air molecules into nerve impulses
-impulses interpreted by brain as sound
-organ of hearing = ear
Structures w/in temporal bones of skull
-external ear
-middle ear
-inner ear
Pinna
funnels sound waves
L-shaped external ear
external auditory canal
Tympanic membrane
= eardrum
-paper thin c.t.
*stretched tightly across opening b/w: external auditory canal and middle ear cavity
-vibrations strike and cause to vibrate
Otitis externa
infection of the external ear canal
Otitis media
infection of the middle ear
Middle ear
-hollowed out area in temporal bone
-filled with air
- 3 ossicles: hammer, anvil, stirrup
-opening of the eustachian tube
Ossicles
-function to transmit vibrations
-act as system of levers that transmit sound wave vibrations from tympanic membrane to cochlea
-vibrations are decreased in size and increased in force
Malleus
outermost bone, attached to tympanic membrane
Incus
middle bone
Stapes
attached to membrane covering oval window of cochlea
Eustachian tube
auditory tube
-connects middle ear cavity with pharynx
-equalizes air pressure on two sides of tympanic membrane
Inner ear
-structures contribute to hearing and equilibrium
-includes: cochlea, organ of corti, vestibule, semicircular canals
Cochlea
-snail shaped spiral cavity
- contains hearing portion of inner ear
Organ of Corti
- w/in cochlea
-fluid filled portion (endolymph) that makes up receptor organ of hearing - contains HAIR CELLS (hearing receptors)
Process of Hearing
- sound wave vibrations cause tympanic membrane and ossicles in middle ear to vibrate
-vibration goes to the cochlea which houses the organ of corti
-preilymph vibrates causing distortion of hair cells
-nerves impulses are generated (Vestibulocochlear nerve)
-impulses travel to brain and are interpreted as sound
Vestibulocochlear nerve
CN 8
convey sensory for hearing and balance
Equilibrium- Inner ear
-mechanical sense
-helps animal maintain balance by keeping track of head’s position and movements
Equilibrium receptors in inner ear
vestibule = linear motion
semicircular canals = rotary motion
Vestibulocochlear nerve
sends info which is integrated in the brain
Vestibular disease
can be caused by central or peripheral vestibular system, idiopathic vestibular disease
-head tilt, loss of balance
-inner ear disease or vestibulocochlear nerve lesion
Eye components
-function to help form an accurate visual image
-not to detect the image
Photoreceptors
-located in single layer of cells in retina
-function is to detect the image
-generate visual nerve impulses
Outer fibrous layer of eyeball
cornea, sclera
Middle vascular layer of eyeball
choroid, iris, ciliary body
Inner nervous layer of eyeball
retina
Cornea
-transparent; admits light to interior of eye
-orderly arrangement of collagen fibers
-no blood vessels; many pain receptors
Sclera
white of the eye
limbus
junction of the cornea and sclera
Uvea
Middle vascular layer of eye
-choroid
-iris
-ciliary body
Choroid
-lies b/w sclera and retina
-consists mainly of pigment and blood vessels
*tapetum lucidum = highly reflective area in rear of eye (not present in humans and swine)
Iris
-pigmented muscular diaphragm
-controls amount of light that enters the posterior part of eye
*pupil = opening in center of iris
Ciliary body
-ring shaped behind iris
-contains tiny muscles that adjust shape of the lens to allow near and far vision
Retina
-lines back of eye
-component of fundus
-contains rods and cones, sensory receptors for vision
Aqueous compartment of eye
-located in front of lens
-subdivided by iris: anterior and posterior chamber
-contains clear watery fluid = aqueous humor
Where is aqueous humor produced?
posterior chamber by cells of ciliary body
Vitreous compartment/ chamber
-clear gelatinous fluid = vitreous humor
-fills whole back of eyeball behind lens and ciliary body
Lens
-elastic and biconvex
-helps focus clear image on the retina through accommodation process
Nuclear sclerosis
aka lenticular sclerosis
-normal age related change
-can still see the back of the eye
-compression makes lens less elastic and visible
Optic disc
“blind spot” of eye
-site where nerve fibers on inside of retina converge and leave the eye to form optic nerve
Photoreceptor cells
-neurons with dendrites modified into sensory receptors for light
rod= more sensitive to light
cones = more sensitive to color and detail
4 refractive media
cornea, aqueous humor, lens, vitreous humor
Nerve fibers leave the eye and form
the optic nerve (CN II)
Conjunctiva
thin moist transparent membrane
covers front portion of eyeball
Bulbar conjunctiva
covers front portion of eyeball
Palpebral conjunctiva
lines interior surfaces of eyelids
Conjunctival sac
space b/w bulbar and palpebral portions of conjunctiva
Tear drainage system
-lacrimal puncta
-lacrimal sacs
-nasolacrimal duct
3 main layers of tears
- inner mucous layer - from cells in conjunctiva
- middle tear layer - from lacrimal glands and accessory lacrimal glands of third eyelid
- outer oily layer -from tarsal or meibomian glands
Not enough tears
KCS- keratoconjunctivitis sicca
