Special Senses

palpebrae

upper and lower eyelids

palpebral fissure

opening between eyelids

lacrimal caruncle

fleshy elevation at the medial commissure; produces a whitish oily secretion

conjunctiva

Delicate membrane lining the eyelids and covering the eyeball

conjunctivitis

inflammation of the conjunctiva

lacrimal apparatus

the structures that produce, store, and remove tears

lacrimal puncta

pores that drain the tears

lacrimal canaliculi

drain lacrimal fluid from eyes medially

lacrimal gland

produces tears

nasolacrimal duct

drains tears into the nasal cavity

lysosyme

Antibacterial enzyme, attacks the cell wall of some bacterial

fibrous layer of eye

Sclera and Cornea; outermost layer

vascular layer of eye

middle layer

retina

Contains sensory receptors that process visual information and sends it to the brain

sclera

white of the eye

cornea

The clear tissue that covers the front of the eye

Canal of Schlemm (scleral venous sinus)

drains aqueous humor

choroid

contains blood vessels and melanin

ciliary body

changes the shape of the eye and makes aqueous humor

ora serrata

the serrated boundary between the ciliary muscle and the retina

ciliary processes

folds of ciliary body that secrete aqueous humor

suspensory ligaments

hold the lens in place

ciliary muscle

smooth muscle portion of the ciliary body, which contracts to assist in near vision

lens

Focuses light onto retina

iris

Colored part of the eye

radial muscles of iris

contracts to dilate pupil

circular muscles of the iris

Smooth muscle that contracts to constrict pupil

anterior segment/cavity

between lens and cornea; filled with aqueous humor

Anterior chamber

between cornea and iris

Posterior chamber

between iris and lens

posterior segment/cavity

between lens and retina; contains gel-like vitreous humor

pupil

opening in the center of the iris

aqueous humor

fluid found anterior to the lens; nourishes the eye

viterous humor

jellylike substance posterior to the lens; holds the retina in place

refraction

The bending of a wave as it passes from one medium to another

macula lutea

a yellowish central area of the retina that is rich in cones and that mediates clear detailed vision

fovea centralis

pinpoint depression in the center of the macula lutea that is the site of sharpest vision

neural layer of retina

houses photoreceptors and other associated neurons

pigmented layer of retina

absorbs light and prevents it from scattering in the eye

rods

receptors that detect black, white, and gray

cones

color vision

photoreceptor layer

contains rods and cones

bipolar cell layer

rods and cones synapse on these cells

ganglion cell layer

A layer of the retina closest to the center of the eye, containing ganglion cells

optic disc (blind spot)

Region at the back of the eye where the optic nerve meets the retina. No photoreceptors are here

optic chiasm

point at which optic nerve fibers cross in the brain

optic tract

leads from optic chiasma to terminate in lateral geniculate body

optic radiations

the diffuse neural pathways from each lateral geniculate nucleus to the primary visual cortex of the same hemisphere

fixation

looking at a motionless object

saccades

moving the eyes rapidly from one location to another

smooth pursuit

tracking objects

pretectal nuclei

involved with pupillary reflexes

external ear

outer structures of the ear that collect sound

middle ear

conveys sound vibrations to the oval window

inner ear

contains cochlea, semicircular canals, and vestibule

auricle

external portion of the ear

helix

rim of ear

lobule

earlobe

External acoustic (auditory) meatus

transmits sound waves from the auricle to the tympanic membrane of the middle ear

tympanic membrane

eardrum; turns sound waves into vibrations

pharyngotympanic (auditory) tube

channel between the middle ear and throat

ossicles

three tiny bones in the middle ear; transmits vibrations to the inner ear

malleus

hammer; first of the three auditory ossicles of the middle ear

incus

anvil; middle of the three auditory ossicles of the middle ear

stapes

stirrup; last of the three auditory ossicles of the middle ear

round window

A membrane-covered opening in the inner wall of the middle ear that compensates for changes in cochlear pressure.

middle ear infections

Usually result when infections of the nose and throat move through the auditory tubes

More common in children because their auditory tubes are horizontal, allowing easier access to bacteria

bony labyrinth

winding tunnels located in the inner ear

membranous labyrinth

membrane-covered tubes inside the bony labyrinth

perilymph

fluid contained in the bony labyrinth of the inner ear

endolymph

fluid within the membranous labyrinth of the inner ear

vestibule

the area between cochlea & semicircular canals. detects linear acceleration and head position

otolith organs

the mechanical structures in the vestibular system that sense both linear acceleration and gravity

utricle

horizontal sac; detects side to side and forward backward motions

saccule

vertical sac; detects up/down and forward/backward motions

semicircular canals

three canals within the inner ear that contain specialized receptor cells that generate nerve impulses with rotational acceleration

anterior semicircular canal

nodding yes

lateral semicircular canal

saying no

posterior semicircular canal

ear to shoulder

equilibrium pathway

CN8 to the vestibular nuclei; integration occurs and info sent out thru CN3, 4, 6, 11 and the vestibulospinal tract. Impulses to VPN for conscious awareness of balance

motion sickness

Effect when visual and/or motor feedback is inconsistent with vestibular info

inferior cerebellar peduncles

part of equilibrium pathway; aid in balance and coordinating postural adjustments

cochlea

site of hearing receptors

modiolus

bony core of cochlea

helicotrema

the opening that connects the tympanic and vestibular canals at the apex of the cochlea

oval window

entrance to the inner ear

scala tympani

inferior chamber of cochlea

scala vestibuli

superior chamber of cochlea

cochlear duct

middle chamber of cochlea that houses the organ of Corti

vestibular membrane

separates the cochlear duct from the scala vestibuli

tectorial membrane

A rigid membrane in the cochlear duct, against which the stereocilia in the organ of Corti bend when stimulated by vibration, setting off an action potential.

basilar membrane

separates the cochlear duct from the scala tympani

Rotational acceleration/deceleration

sensation sensed in the semicircular canals

linear acceleration/deceleration

sensation sensed in the vestibule

stereocilia

hair-like extensions on the tips of hair cells in the cochlea

organ of corti

sensory organ of hearing

organ of corti receptor type

mechanoreceptor

Fast auditory pathway

CN8 to the cochlear nuclei; decussation and movement toward lateral lemniscus and inf. colliculus, synapse in med. geniculate nuclei to auditory cortex

fast auditory pathway example

jumping from a loud noise

slow auditory pathway

CN 8 to cochlear nuclei to superior olivary nucleus, lateral lemniscus to inferior colliculus, synapse in med. geniculate nuclei to auditory cortex