BIOL 252 1st Edition Lecture 6 Outline of Last Lecture I Enteric Nervous System II Poll Everywhere III Single Innervation IV Control of Autonomic Function V Sensory Systems Outline of Current Lecture I Gustation II Olfaction III Hearing and Equilibrium IV Poll Everywhere V Sensory Coding VI Cochlear Tuning VII Projection Pathway VIII Equilibrium Current Lecture I Gustation a b Projection Pathway i Taste 1 CN VII from taste buds over anterior 2 3 of tongue 2 CN IX from taste buds of posterior 1 3 of tongue 3 CN X from taste buds of palate pharynx epiglottis ii General sensation 1 CN V from anterior 2 3 of tongue 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 2 CN IX from posterior 1 3 of tongue 3 CN X from palate pharynx epiglottis iii Sent to 2 destinations 1 Hypothalamus a Controls autonomic reflexes gagging salivation vomiting 2 Postcentral gyrus a Conscious sense of taste II Olfaction a Cribriform foramina cranial nerve I olfactory b W in olfactory epithelium nerve endings bulb tract c 3 cell combo olfactory cells supporting cells basal cells olfactory epithelium III d e Cranial nerve 1 projects to primary olfactory cortex in temporal lobe i Cranial nerve V also carries info about irritation etc Hearing and Equilibrium a Pitch perception of high vs low i High pitch high frequency where frequency cycles second b Loudness perception of sound intensity amplitude i Low intensity not very loud ii After 120 decibels all sounds same iii c Anatomy of the Ear i Outer Ear brings in sound 1 Auricle auditory canal tympanic membrane ii Middle ear transmits vibrations from tympanic membrane to inner ear 1 3 little bones ossicles a Malleus incus stapes hammer anvil stirrup 2 Why is the temporal membrane filled w air a So the same pressure is on both sides b Maintain air pressure by auditory eustacian tube which leads to pharynx throat iii Inner ear 1 2 Cochlea bony structure a b Cross section c 3 Openings a Oval window in contact w stapes b Round window 4 Cochlear duct spirals around 2 5 times a Perilymph surrounds it 5 Organ of corti runs all through cochlear duct a Sandwiched between 2 membranes i Above tectorial ii Cell at bottom basilar b iv Excitation of hair cells 1 Mechanically gated ion channels at tip of stereocilia respond to vibrations 2 Un stimulated ion gate closed stimulated ion gate open 3 Hair cells do not regenerate 4 Fewer inner hair cells vs outer a Inner perception of sound b Outer discriminating sounds IV V VI VII VIII Poll Everywhere a 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 Diagnose the location of the deficit i Answer Incus Sensory Coding a Amplitude degree of vibration corresponds to degree of stimulation i Small motion small vibration b Frequency pitch depends on which part of basilar membrane vibrates uses principle of labeled line code certain stimulated regions sent to different parts of the 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 Cochlear Tuning a Outer hair cells shorten reducing basilar membrane s mobility responsible for ability to focus in noisy environments b Inhibitory neurons synapse near base of inner hair cells Projection Pathway a Inferior colliculus auditory reflex head turning b Superior olivary nucleus reflexes for cochlear tuning locating sounds in space binaural hearing Equilibrium a Inner ear responsible for senses of equilibrium angular acceleration linear acceleration static equilibrium b Semicircular ducts in places at 90 degrees to each other i Responsible for angular acceleration c Organ of equilibrium the macula i ii Similar to organ of corti for hearing iii Macula supporting cells otoliths ear stones of calcium carbonate to add density hair cells otolithic membrane iv Static equilibrium when head is tilted heavy otolithic membrane sags bending stereocilia