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