Chapter 27: Sensory Systems

audition

sense of hearing

auricle

cartilaginous outer ear

basilar membrane

stiff structure in the cochlea that indirectly anchors auditory receptors

bipolar neuron

neuron with two processes extending from the cell body, typically in opposite directions

candela

(cd) unit of measurement of luminous intensity (brightness)

circadian

describes a time cycle about one day in length

cochlea

whorled structure that contains receptors for transduction of the mechanical wave into an electrical signal

cone

weakly photosensitive, chromatic, cone-shaped neuron in the fovea of the retina that detects bright light and is used in daytime color vision

cornea

transparent layer over the front of the eye that helps focus light waves

fovea

region in the center of the retina with a high density of photoreceptors and which is responsible for acute vision

free nerve ending

ending of an afferent neuron that lacks a specialized structure for detection of sensory stimuli; some respond to touch, pain, or temperature

glabrous

describes the non-hairy skin found on palms and fingers, soles of feet, and lips of humans and other primates

glomerulus

in the olfactory bulb, one of the two neural clusters that receives signals from one type of olfactory receptor

Golgi tendon organ

muscular proprioceptive tension receptor that provides the sensory component of the Golgi tendon reflex

gustation

sense of taste

hyperopia

(also, farsightedness) visual defect in which the image focus falls behind the retina, thereby making images in the distance clear, but close-up images blurry

incus

(also, anvil) second of the three bones of the middle ear

inner ear

innermost part of the ear; consists of the cochlea and the vestibular system

iris

pigmented, circular muscle at the front of the eye that regulates the amount of light entering the eye

kinesthesia

sense of body movement

labyrinth

bony, hollow structure that is the most internal part of the ear; contains the sites of transduction of auditory and vestibular information

lens

transparent, convex structure behind the cornea that helps focus light waves on the retina

malleus

(also, hammer) first of the three bones of the middle ear

mechanoreceptor

sensory receptor modified to respond to mechanical disturbance such as being bent, touch, pressure, motion, and sound

Meissner’s corpuscle

(also, tactile corpuscle) encapsulated, rapidly-adapting mechanoreceptor in the skin that responds to light touch

Merkel's disc

unencapsulated, slowly-adapting mechanoreceptor in the skin that responds to touch

middle ear

part of the hearing apparatus that functions to transfer energy from the tympanum to the oval window of the inner ear

muscle spindle

proprioceptive stretch receptor that lies within a muscle and that shortens the muscle to an optimal length for efficient contraction

myopia

(also, nearsightedness) visual defect in which the image focus falls in front of the retina, thereby making images in the distance blurry, but close-up images clear

nociception

neural processing of noxious (such as damaging) stimuli

odorant

airborne molecule that stimulates an olfactory receptor

olfaction

sense of smell

olfactory bulb

neural structure in the vertebrate brain that receives signals from olfactory receptors

olfactory epithelium

specialized tissue in the nasal cavity where olfactory receptors are located

olfactory receptor

dendrite of a specialized neuron

organ of Corti

in the basilar membrane, the site of the transduction of sound, a mechanical wave, to a neural signal

ossicle

one of the three bones of the middle ear

outer ear

part of the ear that consists of the auricle, ear canal, and tympanum and which conducts sound waves into the middle ear

oval window

thin diaphragm between the middle and inner ears that receives sound waves from contact with the stapes bone of the middle ear

Pacinian corpuscle

encapsulated mechanoreceptor in the skin that responds to deep pressure and vibration

papilla

one of the small bump-like projections from the tongue

perception

individual interpretation of a sensation; a brain function

pheromone

substance released by an animal that can affect the physiology or behavior of other animals

presbyopia

visual defect in which the image focus falls behind the retina, thereby making images in the distance clear, but close-up images blurry; caused by age-based changes in the lens

proprioception

sense of limb position; used to track kinesthesia

pupil

small opening through which light enters

reception

receipt of a signal (such as light or sound) by sensory receptors

receptive field

region in space in which a stimulus can activate a given sensory receptor

receptor potential

membrane potential in a sensory receptor in response to detection of a stimulus

retina

layer of photoreceptive and supporting cells on the inner surface of the back of the eye

rhodopsin

main photopigment in vertebrates

rod

strongly photosensitive, achromatic, cylindrical neuron in the outer edges of the retina that detects dim light and is used in peripheral and nighttime vision

Ruffini ending

(also, bulbous corpuscle) slowly-adapting mechanoreceptor in the skin that responds to skin stretch and joint position

semicircular canal

one of three half-circular, fluid-filled tubes in the vestibular labyrinth that monitors angular acceleration and deceleration

sensory receptor

specialized neuron or other cells associated with a neuron that is modified to receive specific sensory input

sensory transduction

conversion of a sensory stimulus into electrical energy in the nervous system by a change in the membrane potential

stapes

(also, stirrup) third of the three bones of the middle ear

stereocilia

in the auditory system, hair-like projections from hair cells that help detect sound waves

superior colliculus

paired structure in the top of the midbrain, which manages eye movements and auditory integration

suprachiasmatic nucleus

cluster of cells in the hypothalamus that plays a role in the circadian cycle

tastant

food molecule that stimulates gustatory receptors

taste bud

clusters of taste cells

tectorial membrane

cochlear structure that lies above the hair cells and participates in the transduction of sound at the hair cells

tonic activity

in a neuron, slight continuous activity while at rest

tympanum

(also, tympanic membrane or ear drum) thin diaphragm between the outer and middle ears

ultrasound

sound frequencies above the human detectable ceiling of approximately 20,000 Hz

umami

one of the five basic tastes, which is described as “savory” and which may be largely the taste of L-glutamate

vestibular sense

sense of spatial orientation and balance

vision

sense of sight