11 21 2013 Audition Vestibular Sense Body Senses and Chemical Senses Sound is dealt with almost exclusively as a wave Final exam information Audition Characteristics of a wave Wavelength Amplitude o Explain properties of volume and pitch Pitch coded by frequency in such a way that Low frequency sound waves greater distance between peaks are base notes Measured in Hertz High frequency treble notes If you have a base note that is moving quickly the loudness of the sound is found by the more air that moves Timbre Attribute of sound that makes the same pitch and volume sound different on two different instruments o Produced by vibrations of the acoustic instrument o Occurs with natural acoustic instruments o Has to be replicated in electric instruments Reissuance vibration set up in an object when presented by a sound wave Volume measured in decibels Structures of the Ear Outer Ear waves o Pinna not moveable in humans Purpose to capture the o Auricle opening that exists in the outer ear Funnels sound down the external ear canal Ear canal o Tympanic membrane sound is funneled to here o Purpose collect and channel frequencies to ear drum Middle Ear Auditory nerve o Contains the Tympanic membrane o Lined with mucous membrane that is similar the sinus o Allow for pressure equalization forces the ear drum out Bones of the middle ear have 3 functions o 1 Transmitting vibration of ear drum o 2 Amplify the force of the vibration Done by change in surface area The stapes is positioned on a part of the inner ear called the oval Middle ear window Made of bone Hollow vessel that contains fluid and fluid is set into vibration by stapes How it works because pressure waves has increased there is an inward movement by the stapes Inward movement of stapes leads to outward movement of stapes Attenuation Reflex 30 40 decibel reduction Used when we speak There are two muscles attached to bone Tensor tympanic malleus Stampedes footplate of the stapes control of the muscles Inferior colluci are the auditory relays in the brain stem and are in Low frequency these two muscle masses contract and the stapes is moved away from the oval window dampens the force of the vibration Used in a reflexive protective measure o Has a latency too it Maybe 40 seconds o If the loud sound is a rapid change attenuation reflex can handle it Inner ear structures Contains a bony structure that is a separate entity that can be dissected from the temporal lobe Contains 2 sensory systems 8th nerve auditory nerve or the vestibular cochlear nerve Bony labyrinth hollow In it there is another structure that conforms to this and is membranous Membranous labyrinth Membranous labyrinth conforms to the shape but has a smaller outer diameter than the Both spaces are filled with fluid Membranous labyrinth fluid endolymph inside the membranous Fluid between Bony labyrinth and membranous labyrinth Perilymph Fluids do not communicate with each other Vestibular sense contained in two portions of the inner ear o Semicircular canals there are 3 named for approximate positions Anterior Lateral Posterior Are closely approximated to the 3 planes of space o Vestibular Sacs there are two receptor areas Saccule 4 Utricle 14 Auditory Sense o Cochlea Oval window Receives its energy from the oval window and pressure waves travel through the window and dissipated through the round window Round window Membranous Labyrinth Bony Labyrinth dissected away 2 and revolutions Oval window and round window Cochlea Hair cells There are 3 chambers When the vibration is set up in the scale vestibule oval window travels through the Scala Media The round window is located at the base of the Scala Tympani Organ of corti where the receptors are electrical signals happen here o Picked up by the dendrites o Axons of the ganglion cells are located along the length of the Purpose of vestibular membrane allow inner ear to regulate chemical composition of this fluid around the hair cells Cells have optimum performance in terms of transmission of pressure it doesn t exist doesn t resist transmission vibration at all Fine tune the pitch we are detecting Outer hair cells are associated with protein molecules that can change their length can contract Inner hair cells code for a particular pitch Outer hair cells amplify the specificity of that code so we have a better discrimination Base of hair cell will move differently than the apex move in separate ways Result physical force is applied to hair that extend from apex and that is what is coded for as a signal Place coding of Pitch Traveling wave on basilar membrane o High frequency sounds affect perfedtially to the base of the basilar membrane close to the vestibule As you go up toward the apex membrane in responding to increasingly lower frequencies High frequency base Low frequency apex Tonotopic representation Helmholtz came up with this The way we discriminate most pitches The Cochlea seen as a straight tube Hair cells Stereocilia o All of the hair cells are interconnected with fibers called tip links and the place at which they re connected at various hair cells are called insertional plaques o What happens here when vibration is established in stereocillia if displaced to shorter cilia then tension on the tip links will be reduced and if they are displaced to the other direction tension on tip links will be increased Tectorial membrane Tip Links Movement toward kinocilium opens ion channel o Potassium and calcium enter o Produces receptor potential Support for Place Theory Observation of Traveling waves Antibiotics o Hair cell loss at base o Loss of high frequency sounds Cochlear implants Rate Theory Low frequencies Auditory system is doing this hair cells in the organ of corti are phase locked with the frequency White nose o Increase rate of turning on and off the pitch will increase o We are coding for frequency in change of pitch even though all of basilar membrane is being stimulated Cochlear implants o If you take someone who has them and you turn on and off the electrodes at a low frequency rate they experience a tone that changes with frequency and only experience in the electrode array is being turned on and off at the apex Central Auditory Pathways Afferent pathways o Cochlear division of c n VIII o Cochlear nuclei First place where auditory information goes This level of the nervous system auditory information is ipsilateral After cochlear nuclei everything becomes bilateral o Superior olivary nuclei o Inferior