BIOL 252 1st Edition Lecture 6 Outline of Last Lecture I. Enteric Nervous System II. Poll EverywhereIII. Single InnervationIV. Control of Autonomic FunctionV. Sensory SystemsOutline of Current LectureI. GustationII. OlfactionIII. Hearing and EquilibriumIV. Poll EverywhereV. Sensory CodingVI. Cochlear TuningVII. Projection PathwayVIII. EquilibriumCurrent LectureI. Gustationa.b. Projection Pathwayi. Taste1. CN VII: from taste buds over anterior 2/3 of tongue2. CN IX: from taste buds of posterior 1/3 of tongue3. CN X: from taste buds of palate, pharynx, epiglottisii. General sensation1. CN V: from anterior 2/3 of tongueThese 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.2. CN IX: from posterior 1/3 of tongue3. CN X: from palate, pharynx, epiglottisiii. Sent to 2 destinations1. Hypothalamusa. Controls autonomic reflexes: gagging, salivation, vomiting2. Postcentral gyrusa. Conscious sense of tasteII. Olfactiona. Cribriform foramina: cranial nerve I (olfactory)b. W/in olfactory epithelium = nerve endings => bulb => tractc. 3 cell combo: olfactory cells, supporting cells, basal cells = olfactory epitheliumd.e. Cranial nerve 1 projects to primary olfactory cortex in temporal lobei. Cranial nerve V also carries info about irritation, etc.III. Hearing and Equilibriuma. Pitch: perception of high vs. lowi. High pitch = high frequency where frequency = cycles/secondb. Loudness: perception of sound intensity (amplitude)i. Low intensity = not very loudii. After 120 decibels, all sounds sameiii.c. Anatomy of the Eari. Outer Ear-brings in sound1. Auricle, auditory canal, tympanic membraneii. Middle ear-transmits vibrations from tympanic membrane to inner ear1. 3 little bones = ossiclesa. Malleus, incus, stapes (hammer, anvil, stirrup)2. Why is the temporal membrane filled w/ air?a. So the same pressure is on both sidesb. Maintain air pressure by auditory (eustacian) tube, which leads to pharynx (throat) iii. Inner ear1.2. Cochlea-bony structurea.b. Cross section:c.3. Openingsa. Oval window: in contact w/ stapesb. Round window4. Cochlear duct: spirals around 2.5 timesa. Perilymph surrounds it5. Organ of corti: runs all through cochlear ducta. Sandwiched between 2 membranesi. Above = tectorialii. Cell at bottom = basilar b.iv. Excitation of hair cells1. Mechanically gated ion channels at tip of stereocilia respond to vibrations2. Un-stimulated: ion gate closed; stimulated: ion gate open3. Hair cells do not regenerate 4. Fewer inner hair cells vs. outera. Inner: perception of soundb. Outer: discriminating soundsIV. Poll Everywherea. 39-year-old woman cannot hear properly. Upon examination, she is able to hear a tuning fork against her forehead, but not while ringing next to her ear. Diagnosethe location of the deficit.i. Answer: IncusV. Sensory Codinga. Amplitude: degree of vibration corresponds to degree of stimulationi. Small motion = small vibrationb. Frequency: pitch depends on which part of basilar membrane vibrates; uses principle of labeled line code (certain stimulated regions sent to different parts ofthe brain)i. Close (proximal) end = near stapes, most sensitive to high pitch ii. Distal end: more resilient, low pitch iii. As you get older, hair cells die off at proximal end (lose high pitch) iv.VI. Cochlear Tuninga. Outer hair cells shorten, reducing basilar membrane’s mobility: responsible for ability to focus in noisy environmentsb. Inhibitory neurons synapse near base of inner hair cells VII. Projection Pathwaya. Inferior colliculus: auditory reflex (head turning)b. Superior olivary nucleus: reflexes for cochlear tuning-locating sounds in space (binaural hearing)VIII. Equilibriuma. Inner ear responsible for senses of equilibrium: angular acceleration, linear acceleration, static equilibriumb. Semicircular ducts: in places at 90 degrees to each otheri. Responsible for angular accelerationc. Organ of equilibrium: the maculai.ii. Similar to organ of corti for hearingiii. Macula: supporting cells, otoliths (ear stones of calcium carbonate to add density), hair cells, otolithic membraneiv. Static equilibrium: when head is tilted, heavy otolithic membrane sags, bending