Bio 449 Lecture 11 Sensory Physiology III Somatosensory

Bio 449 Lecture 11 - Sensory Physiology III 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 349 -379 Lectures 13 -14: Chapters 6 & 7 Sep. 20, 2010

Hair Cells (a) At rest (b) Excitation (c) Inhibition Tip link Stereocilium Hair cell Some channels open Channels closed. Less cation entry hyperpolarizes cell. More channels open. Cation entry depolarizes cell. Primary sensory neuron Action potentials increase No action potentials m. V Action potentials in primary sensory neuron 0 Time m. V – 30 Release Fig. 10 -22 Membrane potential Excitation opens of hair cell ion channels Release Inhibition closes ion channels

Hair Cells

Anatomy of the Ear EXTERNAL EAR MIDDLE EAR INNER EAR Semicircular canals Vestibular appartus Fig. 10 -18 Nerves Cochlea

Vestibular Apparatus SEMICIRCULAR CANALS Superior Cristae within ampulla Horizontal Posterior Cochlea Utricle OTOLITH ORGANS Saccule Maculae Fig. 10 -25

Otolith organs Kinocilium Stereocilia Otoliths Gelatinous layer Hair cells Supporting cells Similar to Fig. 10 -25 Sensory nerve fibers

Otolith Movement

Vestibular Apparatus SEMICIRCULAR CANALS Superior Cristae within ampulla Horizontal Posterior Cochlea Utricle OTOLITH ORGANS Saccule Maculae Fig. 10 -25

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

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

Anatomy of the Ear EXTERNAL EAR The pinna directs sound waves into the ear MIDDLE EAR INNER EAR Oval window Malleus Incus Nerves Stapes Cochlea Ear canal Tympanic membrane Round window To pharynx Eustachian tube Fig. 10 -18

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

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

Transmission of Sound Cochlear nerve Incus Malleus Ear canal Oval window Stapes 5 Vestibular duct (perilymph) 3 2 1 Tympanic membrane 6 Round window 4 Cochlear duct (endolymph) Tympanic duct (perilymph)

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