Special Senses Terms

true sense organs

nerve tissue surrounded by other tissues that enhance response to a certain stimulus

receptor potential

small local electrical charge on a receptor cell brought about by a stimulus; results in release of neurotransmitters or a volley of action potentials that generate nerve signals to the CNS

Weber’s law

the just noticeable difference for a stimulus is proportional to the magnitude

modality

the type of stimulus or sensation a sensory receptor produces

labeled line code

all action potentials are identical; nerve pathways are labeled to identify the origin

phasic receptors

adapt readily; generate a burst of action potentials when first stimulated then quickly reduce or stop signaling even though stimulus continues

tonic receptors

adapt slowly; generate nerve signals more steadily throughout presence of stimulus

exteroceptors

detect external stimuli

interoceptors

detect internal stimuli

proprioceptors

sense body position, muscle tension, and joint movements

free nerve endings

unencapsulated, for pain and temperature, skin and mucous membrane

tactile (merkel) discs

unencapsulated, for light touch and texture, in epidermis basal layer

hair receptors

unencapsulated, coil around a hair follicle, monitor movement of hair, adapt quickly

tactile (massner) corpuscles

encapsulated, for light touch and texture, dermal papillae of hairless skin

krause end bulbs

encapsulated, tactile, in mucous membranes in lips and tongue

lamellar (pacinian) corpuscles

encapsulated, phasic, deep pressure, stretch, tickle, vibration, in periosteum of bone and deep dermis of skin

bulbous (ruffini) corpuscles

encapsulated, tonic, heavy touch, pressure, joint movement

pain nerve endings

encapsulated, discomfort caused by tissue injury or toxic stimulation, typically leading to evasive action, P substance

nociceptors

encapsulated

2 types providing different pain sensations:

fast pain - myelinated fibers; sharp localized pain

slow pain - unmyelinated fibers; longer lasting, dull (diffusing) pain

referred pain

pain in viscera often mistakenly thought to come from the skin or other superficial site

tympanostomy

cutting tympanic membrane and draining fluid from tympanic cavity

modiolus

screw-like spongy bone that the cochlea wraps around

scala vestibuli

superior chamber of cochlea, filled with perilymph

scala tympani

inferior chamber of cochlea, filled with perilymph

scala media (cochlear duct)

middle chamber of cochlea, filled with endolymph

What separates the scala media from the scala vestibuli?

vestibular membrane

What separates the scala media from the scala media?

basilar membrane

stereocilia

long stiff microvilli on hair cells of ear

tectorial membrane

gelatinous structure that rests on top of stereocilia

osteosclerosis

fusion of auditory ossicles that prevents their free vibration

conductive deafness

conditions interfere with transmissions of vibrations to inner ear

sensorineural (nerve) deafness

death of hair cells or any nervous system elements concerned with hearing

static equilibrium

the perception of the orientation of the head when the body is stationary

dynamic equilibrium

the perception of motion or acceleration

linear acceleration

type of dynamic equilibrium, change of velocity in straight line

angular acceleration

type of dynamic equilibrium, change of rate of rotation

macula

a 2 by 3 mm patch of hair cells and supporting cells in saccule and utricle

macula sacculi

lies vertically on wall of saccule

macula utriculi

lies horizontally on floor of utricle

otoliths

in otolithic membrane, calcium carbonate protein granules that add to the weight and inertia and enhance the sense of gravity and motion

crista ampularis

consists of hair cells with stereocilia and a kinocilium buried in a mound of gelatinous membrane

cupula

mound of gelatinous membrane that buries the crista ampularis

lacrimal apparatus

makes, distributes, and drains tears

tunica fibrosa

outer, fibrous layer; cornea and sclera

tunica vasculosa (urea)

middle, vascular layer; choroid, ciliary body, iris

tunica interna

innermost layer; retina and beginning of optic nerve

semicircular canals

utricle

cochlea

vestibulocochlear nerve

retina

choroid

sclera

cornea

lens

ciliary body

suspensory ligaments

iris

optic disc

optic nerve

emmetropia

convergence

What kind of lens is used to correct farsightedness?

A more convex lens, thicker in the middle

What kind of lens is used to correct nearsightedness?

A more concave lens, thinner in the middle

rods

cones

auricle/pinna

tympanic membrane

temporal bone

external acoustic meatus

olfactory bulb and olfactory nerve

olfactory tract

olfactory bulb

olfactory nerves