Presentation is loading. Please wait.

Presentation is loading. Please wait.

Topic 12 The Auditory and Vestibular Systems Lange Biology 463 - Neurobiology.

Similar presentations


Presentation on theme: "Topic 12 The Auditory and Vestibular Systems Lange Biology 463 - Neurobiology."— Presentation transcript:

1 Topic 12 The Auditory and Vestibular Systems Lange Biology Neurobiology

2 Introduction Sensory Systems –Sense of hearing, audition Detect sound Perceive and interpret nuances –Sense of balance, vestibular system Head and body location Head and body movements

3 The Nature of Sound Sound –Audible variations in air pressure –Sound frequency: Number of cycles per second expressed in units called hertz (Hz) –Cycle: Distance between successive compressed patches

4 The Nature of Sound Sound –Range: 20 Hz to 20,000 Hz –Pitch: High pitch = high frequency; low frequency = low pitch –Intensity: High intensity louder than low intensity

5 The Structure of the Auditory System

6 Components of the Middle Ear The Middle Ear

7 5 – Stapedius muscle 9 – Tensor Tympani muscle

8 Sound Force Amplification by the Ossicles –Pressure: Force by surface area –Greater pressure at oval window than tympanic membrane, moves fluids The Attenuation Reflex –Response where onset of loud sound causes tensor tympani and stapedius muscle contraction –Function: Adapt ear to loud sounds, understand speech better The Middle Ear

9 The Inner Ear Anatomy of the Cochlea Perilymph: Fluid in scala vestibuli and scala tympani Endolymph: Fluid in scala media Endocochlear potential: Endolymph electric potential 80 mV more positive than perilymph

10 Physiology of the Cochlea –Pressure at oval window, pushes perilymph into scala vestibuli, round window membrane bulges out The Response of Basilar Membrane to Sound –Structural properties: Wider at apex, stiffness decreases from base to apex Research: Georg von Békésy –Endolymph movement bends basilar membrane near base, wave moves towards apex The Inner Ear

11 Georg von Békésy - Hungarian biophysicist born in Budapest. In 1961, he was awarded the Nobel Prize in Physiology or Medicine for his research on the function of the cochlea in the mammalian hearing.

12 Travelling wave in the Basilar Membrane The Inner Ear

13 The Organ of Corti and Associated Structures The Inner Ear

14 Transduction by Hair Cells –Research: A.J. Hudspeth. –Sound: Basilar membrane upward, reticular lamina up and stereocilia bends outward The Inner Ear

15 Fluids in cochlear canals Upper and middle Internal earExternal ear Pinna External acoustic meatus Air Tympanic membrane Malleus, incus, stapes (ossicles) Oval window Lower Middle ear One vibration Time Spiral organ (of Corti) stimulated Amplification in middle ear Amplitude Pressure

16 Central Auditory Processes Auditory Pathway

17 Techniques for Sound Localization –Horizontal: Left-right, Vertical: Up-down Localization of Sound in Horizontal Plane –Interaural time delay: Time taken for sound to reach from ear to ear –Interaural intensity difference: Sound at high frequency from one side of ear Mechanisms of Sound Localization

18 Interaural time delay and interaural intensity difference Mechanisms of Sound Localization

19 The Sensitivity of Binaural Neurons to Sound Location Mechanisms of Sound Localization

20 Localization of Sound in Vertical Plane –Vertical sound localization based on reflections from the pinna

21 Primary Auditory Cortex –Axons leaving MGN project to auditory cortex via internal capsule in an array –Structure of A1 and secondary auditory areas: Similar to corresponding visual cortex areas Auditory Cortex

22 The Vestibular System Importance of Vestibular System –Balance, equilibrium, posture, head, body, eye movement Vestibular Labyrinth –Otolith organs - gravity and tilt –Semicircular canals - head rotation –Use hair cells, like auditory system, to detect changes

23 Human Anatomy and Physiology, 7e by Elaine Marieb & Katja Hoehn Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings. Figure 15.35: Structure of a macula, p Macula of utricle Macula of saccule Otoliths Hair bundle Kinocilium Stereocilia Otolithic membrane Vestibular nerve fibers Hair cells Supporting cells

24 Human Anatomy and Physiology, 7e by Elaine Marieb & Katja Hoehn Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings. Figure 15.36: The effect of gravitational pull on a macula receptor cell in the utricle, p Otolithic membrane Kinocilium Stereocilia Receptor potential Nerve impulses generated in vestibular fiber Depolarization (Hairs bent towar kinocilium) d Hyperpolarization (Hairs bent away from kinocilium) Increased impulse frequency Excitation Decreased impulse frequency Inhibition

25 Human Anatomy and Physiology, 7e by Elaine Marieb & Katja Hoehn Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings. Figure 15.37: Location and sturcture of a crista ampullaris, p (a) (c) (d) (b) Cupula Cupula at rest Position of cupula during turn Turning motion Fluid motion in ducts Afferent fibers of vestibular nerve Increased firingDecreased firing Position of cupula during turn Ampulla of left ear Ampulla of right ear Horizontal ducts Flow of endolymph Cupula Crista ampullaris Fibers of vestibular nerve

26 The Vestibular System The Semicircular Canal Structure

27 Push-Pull Activation of Semicircular Canals –Three semicircular canals on one side Helps sense all possible head- rotation angles –Each paired with another on opposite side of head –Push-pull arrangement of vestibular axons: The Vestibular System

28 The Vestibulo-Ocular Reflex (VOR) also known as the oculocephalic reflex a reflex eye movement that stabilizes images on the retina during head movement Stabilization occurs by producing an eye movement in the direction opposite to head movement, thus preserving the image on the center of the visual field The Vestibular System

29 END.


Download ppt "Topic 12 The Auditory and Vestibular Systems Lange Biology 463 - Neurobiology."

Similar presentations


Ads by Google