Recording-2025-02-19T20_28_35.716Z

Overview

• Discussion about recent exams and gaps in student understanding.

• Importance of communication styles and tools used to enhance student retention of information.

Introduction to Ear Anatomy and Physiology

• Focus on the external and middle ear anatomy and functionality.

• Connect previous knowledge of acoustics with ear functionality.

• Overview of critical questions related to the auditory system's functions.

Differences Between Peripheral and Central Auditory Systems

• Peripheral auditory system: Consists of the outer and middle ear; external to the brain.

• Central auditory system: Involves processes that occur within the brain, including the cochlear nucleus.

• Understanding this difference helps in organizing information about ear structures.

Structure and Function of the Ear

External Ear

• Pinna (Auricle):

  • Funnel-shaped, captures sound waves, increases surface area for sound collection.

  • Curvature assists in sound filtering, aiding in sound localization, especially in elevation.

• Ear Canal:

  • Tube-like structure that conducts sound waves to the tympanic membrane.

  • Resonates frequencies, amplifying specific sounds while providing protection.

  • Average length: 2.3 to 2.9 centimeters.

• Tympanic Membrane (Eardrum):

  • Thin, concave structure separating external ear from middle ear.

  • Vibrates in response to sound and transmits these vibrations to ossicles.

Middle Ear

• Ossicles:

  • Comprises the malleus (hammer), incus (anvil), and stapes (stirrup).

  • Transmits vibrations from the tympanic membrane to the oval window of the inner ear; crucial for hearing.

• Impedance Matching:

  • Converts air vibrations to fluid vibrations in the cochlea, addressing density differences between air and fluid.

  • Achieved through two mechanisms:

    • Area Ratio: Larger tympanic membrane surface area compared to the smaller oval window.

    • Lever Action: Malleus and incus functioning as levers to amplify sound.

  • Gains of approximately 33 dB achieved from these mechanisms.

Sound Localization

• Interaural Timing Differences (ITD):

  • Sound reaching one ear slightly earlier and louder than the other indicates its direction.

• Pinna Filtering:

  • Frequencies altered by the pinna to assist localization in elevation (up/down, front/back).

• Notch at 10 kHz: Frequency dependent response reflects sound elevation.

Acoustic Reflex and Protection from Loud Sounds

• Acoustic Reflex: Tightening of the muscles around ossicles in response to loud sounds to prevent damage.

• Reflex response typically occurs within 50 to 150 milliseconds.

• Protecting against quick, sharp sounds (e.g., gunshots) requires hearing protection.

Conclusion

• Recap of ear structure functions: Pinna filters and funnels sound, ear canal amplifies and protects, tympanic membrane transmits vibrations, and ossicles aid in impedance matching for effective sound transmission to the cochlea.