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Chapter 16
Sense Organs
| Question | Answer |
|---|---|
| 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 .. | ..an action potential that transmits a signal to the brain |
| The signal travels .. | ..to 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 .. | ..at 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 .. | ..is 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 |
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