Physiology of the Auditory System Quiz
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Questions and Answers

What is the extracellular fluid in the ear?

Perilymph

What is the intracellular fluid in the ear?

Endolymph

What is the base of the Basilar Membrane characterized as?

Narrow and stiff

What is both a mechanoreceptor and an epithelial cell in the ear?

<p>Hair cells</p> Signup and view all the answers

Which part of Hair Cells mutation causes deafness?

<p>Tip links</p> Signup and view all the answers

What separates hairs from hair cell bodies in the ear?

<p>Reticular lamina</p> Signup and view all the answers

What is Characteristic Frequency (CF)?

<p>The frequency at which the sound level reaches a minimum to obtain a criterion displacement for that position on the Basilar Membrane (BM).</p> Signup and view all the answers

How does the displacement of the Basilar Membrane (BM) behave?

<p>The displacement of the BM is not linear with stimulus level, resulting in BM motion being less than the sound level at its Characteristic Frequency (CF) (compressive linearity).</p> Signup and view all the answers

Compare the deflection and excitation of outer and inner hair cells.

<p>Outer hair cells are bent by mechanical shearing (by the tectorial membrane), while inner hair cells are bent by fluid shearing motion.</p> Signup and view all the answers

How do temporal distortions occur in the auditory system?

<p>Temporal distortions occur because low frequencies are transduced after high frequencies on the Basilar Membrane (BM).</p> Signup and view all the answers

How do Basilar Membrane filters become sharper?

<p>Basilar Membrane (BM) filters become sharper when the outer hair cells jump on the BM to amplify the sound.</p> Signup and view all the answers

Study Notes

Cochlear Fluids

  • Perilymph is an extracellular fluid with low potassium and high sodium levels.
  • Endolymph is an intracellular fluid with high potassium and low sodium levels.

Basilar Membrane Structure

  • The base of the Basilar Membrane is narrow and stiff.
  • The apex of the Basilar Membrane is wide and soft.

Hair Cells

  • Hair cells are both mechanoreceptors and epithelial cells.
  • The reticular lamina is a tight junction epithelium that separates the hairs from the hair cell bodies.

Deafness

  • Mutations in the tip links of hair cells can cause deafness.

Traveling Wave and Pressure Wave

  • The pressure wave inside the cochlea is generated by the vibration of the stapes.
  • The pressure wave causes the Basilar Membrane to vibrate.
  • The traveling wave is the vibratory motion of the Basilar Membrane.
  • The amplitude of the traveling wave differs at different locations along the Basilar Membrane.
  • The base of the Basilar Membrane always responds before the apex.

Phase Difference

  • There is a greater phase difference ahead of the traveling wave peak than behind it.

Place Code for Frequency

  • Changes in sound frequency impact the traveling wave peak along the Basilar Membrane, creating a place code for frequency (tonotopy structure).

Envelope of the Traveling Wave

  • The envelope of the traveling wave shows the location of maximum amplitude for pure tone stimuli.

Place Theory and Its Limitations

  • The place theory suggests that the traveling wave for low frequency sounds stretches a long distance and vibrates mostly at the base of the Basilar Membrane.
  • The place theory fails to explain why high frequency sounds stimulate mostly at the base of the Basilar Membrane.
  • Three reasons that explain why the base of the Basilar Membrane likes high frequency sounds:
    • Basilar Membrane width and mass increase.
    • Stereocilia become longer, causing mass to increase.
    • Unknown reason.

Patterns of Excitation

  • The patterns of excitation of complex sounds tell us about frequency, amplitude, and temporal variation.

Mechanical Tuning

  • Mechanical tuning occurs at the Basilar Membrane of the organ of Corti.
  • Mechanical tuning can be described as bandpass filters with steep roll-off for high frequency and shallow roll-off for low frequency.

Frequency Tuning

  • Frequency tuning, or Characteristic Frequency (CF), is the frequency at which the sound level reaches a minimum to obtain a criterion displacement for a specific position on the Basilar Membrane.
  • Mechanical tuning and frequency tuning are two different ways of describing the same quality.

Displacement of the Basilar Membrane

  • The displacement of the Basilar Membrane is not linear with stimulus level.
  • The Basilar Membrane motion is less than the sound level at CF, exhibiting compressive linearity.

Deflection and Excitation of Outer and Inner Hair Cells

  • Outer hair cells are bent by mechanical shearing (by the tectorial membrane).
  • Inner hair cells are bent by fluid shearing motion.

Temporal Distortions

  • The traveling wave brings temporal distortions because low frequency sounds are transduced after high frequency sounds on the Basilar Membrane.
  • The Basilar Membrane has numerous broadly tuned bandpass filters.
  • The outer hair cells can amplify sound by jumping on the Basilar Membrane.
  • The Basilar Membrane filters become sharper due to the outer hair cells.

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Description

Test your knowledge on the physiology of the auditory system with questions about extracellular and intracellular fluids, basilar membrane, hair cells, reticular lamina, and mutations causing deafness. Understand the differences between traveling waves and pressure waves.

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