KIN 1223 Unit 5 Lecture 4 Olfactory Sense Smell Olfactory organs o Called olfactory epithelium Yellowish brown masses Surrounded by mucous membranes Covers roof of nasal cavity and part of nasal septum Contains receptors bipolar neurons with knobs at distal ends of dendrites Olfactory cilia radiate from knobs o Project into nasal cavity o Covered by mucous produced by supporting cells and olfactory glands Mucous dissolves airborne odor molecules o Chemoreceptors stimulated by chemicals dissolved in mucus Once stimulated impulses travel along axons grouped into fascicles of receptor cells Stimulation o Pass through tiny openings in the cribriform plates of the ethmoid bone o Synapse with neurons in olfactory bulbs o Impulse travels along olfactory tracts to olfactory cortex in the uncus Olfactory receptor cells are unique only neurons which are regularly replaced o Only neurons directly in contact with exterior Experience wear and tear Replaced about every 60 days Gustatory Sense Taste Taste buds function as receptors o Taste bud is somewhat spherical o Taste pore opening on free surface o Taste hairs tiny projections microvilli protruding from taste pore Sensitive part of receptor cell o Taste receptors are chemoreceptors Modified epithelial cells not nerve cells Chemicals dissolved in watery fluid surrounding taste buds trigger receptor potential o Sensitive to 5 types of substances 1 Sweet tip of the tongue 2 Sour lateral margins 3 Salty tip and along lateral edges 4 Bitter back of tongue 5 Umami meaty taste produced by amino acids tongue region unknown Auditory Sense Hearing Responds to sound waves caused by compression waves in air o Air is compressed relaxed compressed results in wave Vibration received by outer ear Amplified by middle ear Received transduced and transmitted by inner ear Transmitted to auditory cortex Ear structure o Outer Ear o Middle Ear Pinna auricle gathers and funnels sound External Auditory Meatus contains hairs and modified sweat glands Ceruminous glands secrete cerumen ear wax Tympanic cavity air filled space between outer inner ear Tympanic membrane Ear drum semitransparent membrane at end of ear canal Oval margin Cone shaped apex directed inward Outer surface thin layer of skin Inner surface mucous membrane Tympanic reflex o Initiated by loud sound muscles contract o Make tympanic membrane oval window rigid o Protects inner ear less vibration transmitted Auditory Ossicles transmit vibrations from eardrum to inner ear may amplify sound Malleus hammer attached to tympanic membrane o Tensor Tympani Muscle pulls Malleus inward Attached to medial surface of Malleus wall of auditory tube Tightens tympanic membrane damps or reduces vibration Incus anvil transmits vibration to the Stapes Stapes staple attached to the oval window opening to inner ear o Stapedius pulls Stapes outward away from oval window Attached to posterior side of Stapes posterior wall of tympanic cavity Also damps vibration Eustachian tube Connects middle ear with nasopahrynx Allows air to pass between tympanic cavity and exterior via throat and mouth o Maintain equal air pressure on both sides of tympanic membrane With unequal pressure eardrum can t vibrate When pressure changes must open system to equalize pressure between tympanic cavity and the outside Swallow yawn and chew Auditory tube normally flattened o Inner Ear Hearing Labyrinth complex system of tubes and chambers which comprises the inner ear Osseous labyrinth Passageways lined with endosteum in temporal bone filled with fluid perilymph o Divided into structurally and functionally into 3 different regions Cochlea actual organ that functions in hearing Divided into 3 parallel compartments o Scala vestibuli Upper bony compartment Begins at oval window and opens into middle ear Comprise the osseous labyrinth Filled w perilymph Flows form one chamber to the other through helicotrema opening at apex of cochlea o Scala tympani Stapes attached to membrane of oval window Terminates at apex of cochlea Lower bony compartment Extends from apex of cochlea Back to round window into vestibule o Scala media Cochlear duct Separated from scala vestibule by vestibular Separated from scala tympani by basilar membrane membrane apex Narrow and thick near oval window Becomes wider and thinner toward Supports the Organ of Corti spiral organ contains Cochlear hair cells sound receptors Causes hair cells stereocilia to bend or shear Tips embedded in tectorial membrane Leads to depolarization and transmission of an impulse Impulse interpreted as sound Cochlear hair cells Arranged in 4 rows 1 inner 3 outer rows membranes Located between basilar and tectorial Have long hair like processes stereocillia Specialized microvilli Extend into endolymph of cochlear duct Longest embedded into gel like tectorial membrane Serves as roof of Organ of Corti Basal end synapses with cochlear nerve CN VIII Division of sound frequencies Cause pressure waves Cause movement of basilar membrane At different locations within perilymph of scala vestibule Semicircular canals 3 equilibrium Vestibule opening which serves both Membranous labyrinth floating in perilymph inside bony labyrinth formed by Path of Sound Transmission https www youtube com watch v L4F4zaRqQdk continuous series of sacs and ducts o Gathered and enters external ear o Vibration of tympanic membrane Low frequencies slow vibration High frequencies fast vibration o Moves auditory Ossicles malleus incus stapes o Stapes move oval window Window movement compresses perilymph to scala vestibuli Creates a wave in perilymph o Vibrations transmitted across vestibular membrane to endolymph in cochlear duct o Endolymph pushes down on basilar membrane Moves basilar membrane Moves hair cells stereocilia o Tectorial membrane contact causes hairs to bend Produces receptor potential Leads to transmission of impulse interpreted as sound o Vibrations pass through perilymph of scala tympani Dissipated by movement of membrane covering round window secondary tympanic Response specificity membrane o Areas of the basilar membrane vibrate in response to different sound frequencies o Results in mapping of cochlear duct for sound frequency High frequency basilar end Low frequency apex o Human response 20 20 000 Hz Most sensitive 1500 4000 Hz o Sounds 90dB can cause damage