BIOL 3322 1nd Edition Lecture 14I. Audition (how we hear speak and make music II. If a tree falls in the forest and no ine is around to hear it does it make a sound? No sound waves but no actual sound… w/o a brain or ears to process it there is no actual sound… sound is a product of the brainIII. Sound wavea. Undulating displacement of molecules caused by changing pressureb. 3 properties of sound wave energy i. Frequency - # of cycles per second (pitch)ii. Amplitude – magnitude height of peak (loudness)iii. Complexity – combo of frequencies at least 2 pure tones at a single frequency (timbre uniqueness) iv. Pure tone 1 at a freqv. Fundamental frequencies occur most often – rate at which complex mix of freq occur vi. Overtones – set of sound waves right above fundamental freqc. Perception of soundi. Auditory system converts the physical properties of sound wave energy into electrochemical neural activity that travels to the brainii. Sounds are products of the brain d. Tempanic membrane i. Vibration causes movement of incus malleus and stapes e. Pinnai. Aids in collection of sound collects sound waves from surrounding wavesf. Stimulus of audition i. Pinna catches sound waves and deflects them into the ear canalii. Waves amplified and directed to the eardrum causing it to vibrateiii. Ossicles vibratesiv. Convey vibrations to the oval window v. Vibration of oral window sends waves through cochlear fluid vi. Causing the basilar and tectorial membranes to bendvii. Cause cilia of outer hair cells embedded in the membrane to bend… this bendinggenerates neural activity in hair cells viii. Causing the basilar ad tectorial membranes to bend ix. Vibration of oval window sends waves through cochlear fluidg. Cochlea i. Fluid filled (thick)h. Cross section of the cochlea canal i. Tectorial membrane above cilia ii. Cilia above cochlear neuron iii. Where sounds stimulate in basilar membrane differentiate sound These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.iv. One end is cilia other end is nerve fibers (nerve fiber end attaches to the basilar membrane) i. Auditory receptor i. Middle fluid filled chamber is the organ of corti – made up of receptor cells, ganglia cells and basal membrane j. Unicoi led cochlea a narrow thick base is tuned for high frequencies and a wide thin apex is tuned for low frequencies k. Movement of the basilar membrane in response to sound waves creates a shearing forcethat bends cilia in contact with and near the overlying tectorial membrane l. Binding generates neural activity in the hair cells from which the cilia extendIV. Pathways to auditory cortexa. Cochlear – auditory cochlear nerve – cochlear nuclei – superior olives – midbrain (inferior colliculus) – forebrain (auditory cortex)V. Pathways to the auditory cortexa. Analogous to the visual system, 2 distinct pathways in the auditory system b. One for identifying objects by their sound characteristics c. One for directing our movements by the sounds we hear d. Secondary auditory cortex is just below the primary auditory cortexe. Other side of the primary auditory cortex is the wernickes area VI. Neural activity and hearing pitcha. Tonotopic representation – property of audition in which sound waves are processed in a systematic fashion from lower to higher frequencies i. One side corresponds to apex of cochlear and the other corresponds to the baseof cochlea ii. Systematic from higher to lower – coded as a function b. Cochlear implant i. Electronic device implanted surgically into the inner ear to transduce sound waves into neural activity and allow deaf people to hearc. Low frequencies i. Tonotpic theory does not explain how sounds below 200hz are coded ii. Sounds in the range stimulate all cells on the very apex of the basilar membrane iii. Rate of firing is proportional to frequencyVII. Detecting loudness a. Louder more of everything b. The greater the amplitude of the incoming sound waves the greater the firing rate of bipolar cells in the cochlea c. More intense sound waves trigger more intense movements of the basilar membrane d. Results in greater shearing action of hair cells e. Leads to more neurotransmitter release onto bipolar cells VIII. Detecting locationa. Medial part of the superior olivary complex b. Cells in the hemisphere receive inputs from both ears and calculate the difference in arrival times between the two earsc. Lateral part of the superior olive and trapezoid body (source of sound is detected by the relative loudness on the left or on the right side of the head)d. Calculates extra distance that sound must travel to reach the right