chapter 17; the special senses
wall of eyeballs consists of what 3 layers
1. fibrous tunic (outer layer) 2. Vascaular tunic ( blood supply0 3. Retina ( light strikes vision)
to make this possible the nose contains _____ to _____ receptors for the sense of smell or olfaction , contained within a region called the olfactory epithelium. with a total area of 5 cm
10 mil to 100 mil
humans recognize about _____ different odors
10,000
olfactory nerves
40 or so bundles of axons form the left and right nerves....they terminate in the brain in paired masses of gray matter called __>> olfactory bulbs which are located below the frontal lobes of the cerebrum and lateral to the crista galli of the ethmoid bone.
malleus
"handle" - attached to the internal surface of the tympanic membrane
tinnitus
, a ringing,roaring or clicking in the ears
threshold for taste
- varies for each primary tastes, for bitter substances, such as quinine, is lowest. bc poisonous substances often are bitter, the low threshold (high sensitivity)
conjunctiva
a transparent membrane covering the eyeball and under surface of the eyelid ; pink eye
photophobia
abnormal visual intolerance to light; headaches
otitis media
acute infection of the middle ear cuased mainly by bacteria and associated with infections of the most and throat. symptoms include pain,malaise, fever, and a reddening and outward bulging of the eardrumn which may rupture unless prompt treatment is received
rods
allow us to see in dim light, black white and all shades of gray
olfactory receptors
are the first order neurons of the olfactory pathway. each olfactory receptor is a bipolar neuron with an exposed knob-shaped dendrite and an axon projecting through the cribriform plate and ending in the olfactory bulb
scotoma
area of reduced or lost vision in the visual field [blindspot]
inner hair cells
arranged in a single row, where the outer hair cells are arranged in 3 rows. at the apical top of each hair cell are 40-80 stereocilia that extend into the endolymph of the cochlear duct. despite their stereocilia are actually long,hairlike microvilli arranged in several rows of graded height
olfactory tract
axons of olfactory bulb neurons extend posteriorly , the primary olfactory area is where conscious awareness of smell begins
supporting cells surround about 50 gustatory receptor cells in each taste bud.
basal cells , stem cells found at the periphery of the taste bud near the connective tissue layer, product supporting cells, which then develop into gustatory receptor cells. each gustatory receptor cell has a life span of about 10 days
stapes
base or footplate
refraction
bending; when light rays traveling through a transparent substance pass into a second transparent substance with a diff density they bend at the junction btw the 2 substances
cones
bright light
hyposmia
can't smell; affects half over age of 65 and 75% of those over 80, can be caused by smoking,neurological changes such as head injury,alzheimer disease, or parkinson disease certain drugs like antihistamines, analgesics, or steroids
odorants
chemicals that have an odor and can therefore stimulate the olfactory hairs
iris
colored portion of the eyeball, shaped like a flattened donut. <__> eyes appear brown to black when the iris contains lrg amount of melanin, blue = low melanin, and green when its moderate
supporting cells
columnar epithelial cells of the mucous membrane lining the nose. they provide physical support nourishment and electrical insulation for the olfactory receptors and they help detoxify chemicals that come in contact with olfactory epithelium
6 million ______, 120 million ______
cones,rods
lens
crystallins - layers of an onion , behind pupil and iris, perfectly transparent and lacks bvs
adaptation
decreasing sensitivity to odors occurs rapidly. olfactory receptors adapt by about 50% in the first second or so after stimulation buy adapt very slowly there after.
olfactory pathway
each side of nose about 40 bundles of slender unmyelinated axons of olfactory receptors extend through about 20 olfactory foramina in the cribriform plate of the ethmoid bone.
nearly 10,000 taste buds of an young adult are on the tongue but some are found on the soft palate, pharynx, and epiglottis
each taste bud is an oval body consisting of 3 kinds of epithelial cells; supporting cells,gustatory receptor cells, and basal cells.
otalgia
earache
tympanic membrane
eardrum, thin semitransparent partition btw the external auditory canal and middle ear.
limbic system
emotional brain
macula lutea
exact center of the posterior portion of the retina, at the visual axis of the eye
accessory structures of the eye
eyelids,eyelashes,eyebrows, the lacrimal (tear producing) apparatus, and extrinsic eye muscles
ptosis
falling or drooping of the eyelid
hyperopia or hypermetropia
farsightedness
aqueous humor
fluid that drains into the sinus
pupil
hold in the center of the iris , if bright light is directed into the pupil the reflected light is red bc of the bvs on the surface of the retina.
lobule
inferior or bottom portion of ear
color blindness
inherited inability to distinguish btw certain colors, result from the absence or deficiency of the 3 types of cones.
tonometer
instrument for measuring pressure esp intraocular pressure
astigmatism
irregular curvature
age related macular disease (amd)
leading cause of blindness in those over age 75, afflicting 13 million americans and 2.5 times more common in pack a day smokers than in nonsmokers
olfaction
like al special senses has a low threshold. only a few molecules of certain substances need be present in air to be perceived as an odor
aguesia
loss of sense of taste
incus
middle bone in the series articulates with the head of the stapes
strabismus
misalignment of the eyeballs so that the eyes do not move in unison when viewing an object; cross eyed
constriction of the pupil
narrowing diameter of the hold through which light enters the eye due to the contraction of the circular muscles of the iris
myopia
nearsightedness
emmetropic eye
normal eye
presbyopia
old age eye;losing of vision after age of 40 [20 cm] age 60 [80cm]
the olfactory epithelium consists of 3 kinds of cells;
olfactory receptors,supporting cells, and basal cells
olfactory sensations
only sensations that reach the cerebral cortex without first synapsing in the thalamus. --->> other axons of olfactory tract project to limbic system and hypothalamus; these connections account for our emotional and memory evoked responses to odors.
taste aversion
people and animals quickly learn to avoid a food if it upsets the digestive system. ; longer survival
auricle
pinna; flap of elastic cartilage shaped like the flared end of a trumpet and covered by skin.
intraocular pressure
pressure in the eye
eyelashes & eyebrows
protect eye balls from foreign objects, perspiration and direct rays of the sun
sebacious ciliary glands
release a lubricating fluid into the follicles infection of these glands usually by bacteria causes a painful pus filled welling called a STY
helix
rim of the auricle
earwax or cerumen
secreted by ceruminous glands near the exterior opening the external auditory canal contains a few hairs and specialized sweat glands
vertigo
sensation of spinning or movement in which the world seems to revolve or the person seems to revolve in space
trachoma
serious form of conjunctivits and the greatest single cause of blindness in the world.
eyelids or palpebrae
shade eye during sleep , protect eye from excessive light and foreign objects and spread lubricating secretions over the eyeballs. upper eyelid contains levator papebrae superioris muscle
deafness
significant or total hearing loss, conduction and nerve deafness; about 90 db to 100 db. either impairment of hair cells in the cochlea or damage of the cochlear branch of the vestibulocochlear (8_ nerve
optic disc
site where the optic 2 nerve exits the eyeballs; blind spot
what are the 2 chemical senses
smell and taste
special senses
smell,taste,vision,hearing,and equilibrium
cochlea
snail shaped, a bony spiral canal that makes 3 turns around a central bony core called a modiolus. sections through the cochlea reveal that it is divided into 3 channels: cochlear duct, scala vestibule, and scala tympani
basal cells
stem cells located btw the bases of the supporting cells , continually undergo cell division to produce new olfactory receptors which are replaced after a month
gustation
taste; 5 primary tastes; sour,sweet,bitter,umami (meaty or savory), salty ; all other flavors such as choc, pepper, and coffee are combinators of (touch) sensations
perforated eardrum
tearing of the tympanic membrane
lysozyme
the lacrimal fluid produced by these glands is a watery solution containing salts, some mucus, and lysozyme a protective bacterial enzyme
anosmia
total lack of the sense of smell
cornea
transparent coat that covers the colored iris. helps focus light on the retina , avascular
aqueous humor
transparent watery fluid that nourishes the lens and cornea COMPLETELY replaced every 90 mins.
nyctalopia
vitamin A deficiency or night blindness
sclera
white of the eye