Bio 449Lecture 11 - Sensory Physiology IIISep. 20, 2010 Somatosensory system (conclusion) Equilibrium Audition - the ear Structure Function Terms to Know Hair cell Stereocilia Kinocilium Otoliths (statoconia) Otolith organs (maculae) Semicircular canal Ampulla Cupula Tympanic membrane Auditory ossicles Cochlea Oval window Round window Organ of Corti Basilar membrane Tectorial membrane Readings Lectures 10-12:Chapter 10, pages Lectures 13-14:Chapters 6 & 7

Hair Cells –30 0 Membrane potential of hair cell Action potentials in primary sensory neuron Excitation opens ion channels Inhibition closes ion channels Release mV (a) At rest(b) Excitation(c) Inhibition Tip link Stereocilium Hair cell Primary sensory neuron More channels open. Cation entry depolarizes cell. Channels closed. Less cation entry hyperpolarizes cell. Action potentialsAction potentials increaseNo action potentials Some channels open Time mV Fig

Hair Cells

Anatomy of the Ear Fig MIDDLE EARINNER EAREXTERNAL EAR Nerves Semicircular canals Vestibular appartus Cochlea

Saccule Utricle Maculae SEMICIRCULAR CANALS Superior Horizontal Posterior OTOLITH ORGANS Cristae within ampulla Vestibular Apparatus Fig

Otolith organs KinociliumStereocilia Sensory nerve fibers Supporting cells Hair cells Gelatinous layer Otoliths Similar to Fig

Otolith Movement

Cochlea Saccule Utricle Maculae SEMICIRCULAR CANALS Superior Horizontal Posterior OTOLITH ORGANS Cristae within ampulla Vestibular Apparatus Fig

Orientation of Semicircular Canals Vestibular apparatus Superior canal (nod for “ yes ” ) Horizontal canal (shake head for “ no ” ) Posterior canal (head tilt) Leftright

Endolymph Movement Direction of rotation of the head Endolymph Bone Cupula Hair cells

Anatomy of the Ear Fig MIDDLE EARINNER EAREXTERNAL EAR The pinna directs sound waves into the ear Oval window Nerves To pharynx Eustachian tube Tympanic membrane Round window Stapes Incus Malleus Ear canal Cochlea

Anatomy of the Inner Ear Cochlea Helicotrema Basilar membrane Tympanic duct Round window Cochlear duct Organ of Corti Uncoiled Saccule Oval window Vestibular duct

Anatomy of the Inner Ear Basilar membrane Tympanic duct Cochlear nerve transmits action potentials from the hair cells to the auditory cortex. Tectorial membrane Cochlear duct Vestibular duct Organ of Corti Bony cochlear wall

Transmission of Sound Ear canal Malleus Incus Stapes Cochlear nerve Vestibular duct (perilymph) Round window Tympanic membrane Cochlear duct (endolymph) Tympanic duct (perilymph) Oval window

Transmission of Sound Tectorial membrane Nerve fibers of cochlear nerve Basilar membrane Hair cell Cochlear duct Tympanic duct The movement of the tectorial membrane moves the cilia on the hair cells. Fluid wave