Unit 5 Lecture 4 Notes I Special Senses a Smell taste hearing and equilibrium vision b Olfactory Organs olfactory epithelium contains receptors i Smell sense ii Yellowish brown masses surrounded by mucous membranes iii Cover roof of nasal cavity and part of nasal septum iv Bipolar neurons knobs at distal ends of dendrites 1 Cilia radiate from knobs and project into nasal cavity 2 Covered by mucous produced by supporting cells and olfactory gland dissolves airborne odor molecules v Olfactory Cilia 1 Olfactory receptors chemoreceptors stimulated by chemicals dissolved in mucus 2 Once stimulated impulses travel along axons of receptor cells axons grouped into fascicles 3 Stimulation pass through tiny openings in the cribriform plates of the ethmoid bone a Synapse with neurons in olfactory bulbs b Impulse travels along the olfactory tracts to olfactory cortex in the uncus vi Olfactory receptor cells are only neurons which are regularly replaced 1 Only neurons directly in contact with exterior experience wear and tear 2 Replaced about every 60 days c Gustatory Sense Taste i Taste buds special organs for taste 1 Associated with papillae tiny elevations 2 Modified epithelial cells called taste or Gustatory cells 3 Function as receptors 4 Taste pore opening on free surface 5 Taste hairs protrude from taste pore microvilli sensitive part of the receptors 6 Chemoreceptors modified epithelial cells NOT nerve cells a Chemicals dissolve in watery fluid surrounding taste buds trigger receptor potential ii Sensitive to 5 substances 1 Sweet tip of tongue 2 Sour lateral margins 3 Salty tip and along lateral edges 4 Bitter back of tongue Cilia 5 Umami meaty taste produces by amino acids region unknown d Ear Auditory Hearing i Respond to sound waves caused by compression waves in the air 1 Air is compressed relaxed compressed wave results ii Vibrations received by outer ear amplified by middle ear received transduced and transmitted but inner ear transmitted to auditory cortex iii Outer Ear glands 1 Pinna or Auricle gathers and funnels sound 2 External Auditory Meatus contains hairs and modified sweat a Cerminous glands secrete cerumen ear wax keep iv Middle Ear out foreign objects 1 Tympanic Cavity air filled space between outer and inner ear 2 Tympanic Membrane ear drum semitransparent membrane at end of ear canal a Outer surface thin layer of skin b Inner surface mucous membrane c Cone shaped apex directed inward 3 Auditory Ossicles 3 small bones that amplify sound a Malleus hammer attached to tympanic membrane b c Stapes stirrup attached to the oval window opening Incus anvil transmits vibration to stapes in inner ear d TM surface area 18 20X greater than oval window e Tensor Tympani Muscle making is possible to move fluid behind oval window malleus wall of auditory tube attached to medial surface of i Pulls malleus inward ii Tightens tympanic membrane damps or reduces vibrations f Stapedius posterior wall of tympanic cavity attached to posterior side of stapes i Pulls stapes outward away from oval window ii Also damps vibrations g Tympanic Reflex Initiated by loud sound muscles i Make tympanic membrane and oval window ii Protect inner ear less vibration transmitted connects middle ear with the h Eustachian Tube nasopharynx i Allows air to pass between tympanic cavity and exterior via throat and mouth ii Maintain equal air pressure on both sides of tympanic membrane iii Auditory tube is usually flattened but when pressure changes it must open system to contract ridge II Cochlea a 3 parallel compartments equalize pressure between tympanic cavity and the outside swallow yawn chew v Inner Ear Hearing 1 Labyrinth complex system of tubes and chambers which comprises the inner ear a Osseous Labyrinth divided structurally and functionally passageways in temporal bone i Cochlea functions in hearing 1 Actual organ of hearing 2 Coiled spiral shaped 2 5 turns 3 3 parallel compartments ii Semicircular canals iii Vestibule holes in solid temporal and function 3 equilibrium dizziness opening which serves both structure iv Lines with endosteum v Filled with perilymph b Membranous Labyrinth Labyrinth formed by continuous series of sacs and ducts floating inside bony osseous i Floats in perilymph ii Filled with endolymph c Both filled with fluid i Scala Vestibuli upper bony compartment begins at oval window and terminates at apex of cochlea cochlea back around to round window into vestibule lower bony compartment extends from apex of ii Scala Tympani These two compartments comprise the osseous labyrinth filled with perilymph flows from one chamber to the other through helicotrema opening at apex of cochlea iii Scala Media or cochlear duct membranous labyrinth filled with endolymph between vestibule and scala tympani middle compartments part of 1 Separated from scala vestibule by vestibular membrane 2 Separated from scala tympani by basilar membrane a Basilar Membrane narrow and thick near oval window becomes wider and thinner toward apex Supports the Organ of Corti or Spiral organ that contains sound receptors cochlear hair cells iv Arranged in 4 rows 1 inner row and 3 outer rows 1 Located between basilar and tectorial membrane 2 Have long hair like processes stereocilia specialized microvilli a Extend into endolymph or cochlear duct b Longest embedded into el like tectorial membrane c Serves as rood of organ of Corti d Basal end synapses with cochlear nerve division of CN VIII 3 Division of Sound frequencies cause pressure waves a Cause movement of basilar membrane at different locations within perilymph of scala vestibule III Path of Sound Transmission a Cochlear hair cells causes hair cells stereocilia to bend or shear i Tips embedded in tectorial membrane ii Leads to depolarization and transmission of an impulses that are interpreted as sound b Sound gathers and enters external ear vibrates tympanic membrane i Low frequencies slow vibrations ii High frequencies fast vibrations c Moves auditory ossicles Malleus incus stapes d Stapes moves oval window i Compresses perilymph to scala vertibuli ii Creates a wave in perilymph e Vibrations transmitted across vestibular membrane to endolymph in f Endolymph pushes down on basilar membrane ad moves it moves hair cochlear duct cells stereocilia g Tectorial membrane contact causes hairs to bend i Produces receptor potential and leads to transmission of impulse interpreted as sound h Vibrations pass through perilymph of scala tympani i Dissipated by movement of