Presentation is loading. Please wait.

Presentation is loading. Please wait.

Topic 12 The Auditory and Vestibular Systems Lange

Similar presentations

Presentation on theme: "Topic 12 The Auditory and Vestibular Systems Lange"— Presentation transcript:

1 Topic 12 The Auditory and Vestibular Systems Lange
Biology Neurobiology Topic 12 The Auditory and Vestibular Systems Lange

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 The Middle Ear Components of the Middle Ear

7 5 – Stapedius muscle 9 – Tensor Tympani muscle

8 The Middle Ear 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

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 The Inner Ear 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

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 The Inner Ear Travelling wave in the Basilar Membrane

13 The Inner Ear The Organ of Corti and Associated Structures

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

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

16 Central Auditory Processes
Auditory Pathway

17 Mechanisms of Sound Localization
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

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

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

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

21 Auditory Cortex 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

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 Figure 15.35: Structure of a macula, p. 594.
Macula of saccule Macula of utricle Kinocilium Stereocilia Otoliths Otolithic membrane Hair bundle Hair cells Supporting cells Vestibular nerve fibers

24 Figure 15.36: The effect of gravitational pull on a macula receptor cell in the utricle, p. 595.
Otolithic membrane Kinocilium Ster eocilia Depolarization Hyperpolarization Receptor potential (Hairs bent towar kinocilium) d (Hairs bent away from kinocilium) Nerve impulses generated in vestibular fiber Increased impulse frequency Decreased impulse frequency Excitation Inhibition

25 Figure 15.37: Location and sturcture of a crista ampullaris, p. 596.
Flow of endolymph (a) Crista ampullaris Fibers of vestibular nerve Cupula (b) Turning motion Ampulla of left ear Ampulla of right ear Cupula Cupula at rest Position of cupula during turn Position of cupula during turn Fluid motion in ducts Increased firing Horizontal ducts Decreased firing (c) (d) Afferent fibers of vestibular nerve

26 The Vestibular System The Semicircular Canal Structure

27 The Vestibular System 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:

28 The Vestibular System 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

29 END.

Download ppt "Topic 12 The Auditory and Vestibular Systems Lange"

Similar presentations

Ads by Google