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Chapter 16

Sense Organs

Sensory receptor any structure specialized to detect a stimulus
transduction the conversion of one energy to another
Sensation awareness of the stimulus
Modality the type of stimulus or the sensation it produces
Location encoded by which nerve fibers are sending signals to the brain
Intensity strength of stimuli based on which fibers are firing, and how fast those fibers are firing
Duration how long the stimulus lasts
Classification of Receptors -By stimulus modality -by origin of stimulus
Thermoreceptors respond to heat and cold
Photoreceptors respond to light
Nociceptors respond to tissue injury
Chemoreceptors respond to chemicals
Mechanoreceptors respond to physical deformation of a cell
Exteroreceptors detect stimuli outside the body
Interoceptors detect stimuli in the internal organs
Proprioceptors detect the position and movements of the body
Unencapsulated Nerve Endings sensory dendrites that are not wrapped with CT
Free nerve endings detect pain, heat, cold
Tactile discs detect light touch and pressure
Hair receptors detect hair movement
Encapsulated Nerve Endings nerve fibers wrapped in glial cells or CT
Tactile corpuscles detect light touch and texture, in dermal papillae
End bulbs similar to tactile corpuscles but are found in mucous membranes of the lips and tongue, and conjunctiva
Lamellar corpuscles detect deep pressure, stretch, tickle, and vibration
Bulbous corpuscles detect heavy touch, pressure, and stretching of skin, and joint movement
Nociceptors.. ..occur in skin, mucosa, all organs except brain and liver
Myelinated pain fibers produce fast pain a feeling of sharp, localized pain perceived at the time of injury
Unmyelinated pain fibers produce slow pain longer-lasting, dull, diffuse feeling
Injured tissues release chemicals that stimulate the nociceptors and trigger pain
Referred pain pain in the viscera is mistakenly thought to come from skin
Taste Gustation
Lingual papillae surface protrusions on the tongue
Filiform papillae tiny spikes without taste buds that detect the texture of food
Foliate papillae parallel ridges on the sides of the tongue that lose most of the taste buds by age 2-3
Fungiform papillae widely distributed, but concentrated at the tip and sides of the tongue
Vallate papillae papillae arranged in a V at the rear of the tongue
Taste buds groups of taste cells, supporting cells, and basal cells
Taste cell epithelial cell with taste hairs, which serve as receptors, and that release neurotransmitters at their base to stimulate sensory nerve fibers
Basal cells stem cells that multiply and replace taste cells
Primary tastes salty, sweet, sour, bitter, umame
Smell Olfaction
Olfactory mucosa a patch of olfactory cells, supporting cells, and basal stem cells in the roof of the nasal cavity
Olfactory cells neurons with olfactory hairs, cilia that have binding sites for odor molecules, on the modified dendrite
The axons leave the nasal cavity through .. ..the cribriform foramina and converge to become cranial nerve I
An odorant molecule .. .binds to a receptor on an olfactory hair
Binding.. ..activates a 2nd messenger system
The cell depolarizes triggering .. action potential that transmits a signal to the brain
The signal travels .. the orbitofrontal cortex which receives input from taste and smell and integrates them into our overall perception of flavor
Outer ear a funnel for conducting vibrations to the timpanic membrane
Auricle (pinna) fleshy structure on the side of the head
Auditory canal the passage leading through the temporal bone to the tympanic membrane
Middle ear located in tympanic cavity of the temporal bone
Tympanic membrane the membrane that closes the inner end of the auditory canal and vibrates free in response to the sound
Auditory tube a passageway from the middle ear to the nasopharynx that allows air to enter to equalize air pressure
Auditory ossicles (malleus, incus, stapes) bones that connect the tympanic membrane to the inner ear
Oval window opening covered by the stapes
Inner Ear passage ways in the temporal bone
Vestibule a chamber that contains organs of equilibrium
Cochlea a coiled tube that is the organ of hearing
Scala vestibuli and scala tympani chambers filled with perilymph that connect at the apex of the cochlea
Cochlear duct middle chamber of the cochlea formed by the vestibular membrane and basilar membrane
Spiral organ cells and membranes in the cochlear duct that convert vibrations into nerve impulse
Hair cells sensory cells with short projections called stereocilia
Tectorial membrane gelatinous layer resting on hair cells
- sound an audible vibration of molecules
Transmission air  tympanic membrane  ossicles  perilymph  vestibular membrane  basilar membrane  round window membrane
The reverse for outward vibration ... ..pushes the basilar membrane up and pushes the hair cells against the tectorial membrane
On Inner Hair Cells is.. ..a protein at its tip that functions as a gated ion channel
If the basilar membrane rises, the IHC push against the tectorial membrane bending the stereocilia and pulling open the gate
K+ in the ______ flows through the gate and depolarizes the hair cells endolymph
The hair cells release .... ...a neurotransmitter from the base which stimulates the dendrites of a sensory neuron of cochlear nerve
Equilibrium coordination, balance, and orientation in 3-D space
Saccule and utricle chambers in the vestibule of the inner ear
Macula hair cells and supporting cells in the saccule and utricle
Otolithic membrane gelatinous layer the stereocilia hair cells are embedded in
When the head is tilted .. ..the otolithic membrane sags and bend the stereocilia, stimulating the hair cells
When you begin moving or stop.... ..the otolithic membrane moves at a different speed than the rest of the tissue thus bending the stereocilia and stimulating a nerve signal to advise the brain of a change in velocity
The Semicircular ducts passageways filled with endolymph that detect rotational movements
Crista ampullaris hair cells and supporting cells in the ampulla
Cupula gelatinous cap the stereocilia are embedded in
When the head turns.. the duct rotates but the endolymph lags behind, pushing the cupula thus bending the stereocilia and stimulating the hair cells
The hair cells synapse .. their bases with sensory fibers of the vestibular nerve
Eyebrows facial expressions and protect eyes from glare and sweat
Eyelids block foreign objects from the eye, blink to moisten eyes etc.
Conjuctiva transparent mucous membrane that covers the inner surface of the eyelid and the anterior surface of the eye except the cornea, which secretes mucous to prevent the eyeball from drying
Lacrimal gland gland at the superolateral corner of the orbit that produces tears
Lacrimal punctum pore on medial corner that collect tears  lacrimal canal  lacrimal sac  nasolacrimal duct  nasal cavity
Extrinsic eye muscles muscles attach to the walls of the orbit and the external surface of the eyeball that move the eye
Fibrous layer (tunic fibrosa)
Sclera white of the eye, of dense CT perforated by BV and nerves
Cornea anterior transparent region that admits light into the eye
Vascular layer (tunica vasculosa)
Choroid posterior, highly vascular, pigmented layer
Ciliary body muscular ring around the lens that supports the iris and lens and secretes aqueous humor
Iris Adjustable diaphragm that controls the diameter of the pupil
Inner layer (tunica interna) retina and the beginning of the optic nerve
Optical Components transparent elements that admit light rays
Aqueous humor serous fluid secreted by the ciliary body into the posterior chamber which flows though the pupil into the anterior chamber where it is reabsorbed by the sclera venous sinus
Lens transparent oval suspended behind the pupil by suspensory ligaments attached to the ciliary body
Vitreous body transparent jelly filling the space behind the lens
Retina transparent membrane attached to the back of the eye
Macula lutea center of the retina with the fovea centralis which produces the most finely detailed images
Optic disc where the optic nerves leave the rear of the eye and BV enter and exit the eye
Blind spot optic disc contain no receptor
Pupillary constriction smooth muscles stimulated by the PNS that narrow the pupil and admit less light into the eye
Pupillary dilation myoepithelial cells stimulated by the SNS that widen the pupil and admit more light into the eye
Refraction the bending of light rays
Light that passes through the very center of the eye .. not bent
Light that passes through at an angle..
The refraction by the lens .. ..fine-tunes the image
The Near Response adjustment to close-range vision
Convergence of the eyes orients the visual axis of each eye toward the object in order to focus the image on each fovea
Constriction of the pupil constriction decreases peripheral light rays so that refraction occurs closer to the better-focused center
Accommodation of the lens change in the curvature of the lens that enables you to focus on near objects
Photoreceptor cells absorb light and generate a signal
rods responsible for night vision
Cones responsible for day vision and color vision
Bipolar cells first-order neurons; synapse with rods and cones
Ganglion cells second-order neurons; axons form the optic nerve
Horizontal cells and amacrine cells form horizontal connection between rod, cone, and bipolar cells that enhance the perception of contrast, the edge of objects and changes in light intensity
Visual pigments located in the membrane of discs in rods and cones
Rhodopsin visual pigment of rods consisting of opsin and retinal
Photopsin visual pigment of cones consisting of retinal and three different opsin that have different absorption peaks – for color
Light adaption pupil constricts to reduce light intensity
Dark adaptation pupil dilates to admit more light into the eye
The high sensitivity of rods in dim light that stems in part from the neural convergence.. ..allows for a high degree of spatial summation
Peripheral vision visual acuity decreases rapidly as the image forms away from the fovea centralis
High-resolution images formed when you look directly at something and its image falls on the fovea because the fovea is only cones which do not converge
depth perception the ability to judge how far away objects are
stereoscopic vision... ..depends on two eyes with overlapping visual fields looking at the same object from different angles`
Middle-ear infection infection spreads from the throat up the auditory tube to the tympanic cavity
Conductive deafness any condition that interferes with transmission of vibrations to the inner ear
Sensorineural deafness death of hair cells or any of the nervous elements concerned with hearing
Otosclerosis fusion of the ossicles to each other or fusion of the stapes to the oval window
Cataracts clouding of the lens
Glaucoma elevated pressure within the eye that compresses the b.v. that nourish the retina
Detached retina the retina separates from the wall of the eyeball
Astigmatism deviation in the shape of the cornea causing vertical or horizontal to go out of focus
Hyperopia eyeball is too short, causing difficulty seeing near objects
myopia eyeball is too long, causing for difficulty seeing far objects
Presbyopia reduced ability to accommodate for near vision with age
Created by: babyeyes8761



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