Special Senses Hearing And Vestibular Flashcards
What does the middle ear do?
Impedance matching: the sound wave has been moving through air, but then it moves in liquid
What does the inner ear do?
The cochlea converts the sound waves to action potentials
The scala vestibuli and the scala tympani are continuous, fluid-filled compartments. What is the fluid inside?
Perilymph
What is perilymph similar to?
ECF
Has high Na+ and low K+
The basilar and Reissner’s membranes create a chamber (___) that is isolated from the perilymph. It contains endolymph, which is composed of what?
Scala media
High in K+
Low in Na+
What effect does endolymph have?
Composition of endolymph has a significant effect on the transduction of sound waves in action potentials
Compare and contrast perilymph and endolymph
Perilymph
- found in scala vestibuli and scala tympani
- most similar to ECF/CSF
- high in sodium, low in potassium
Endolymph
- found in scala media
- most similar to intracellular fluid
- high in potassium, low in sodium
What transmit and amplify sound waves from tympanic membrane to oval window of cochlea
Ossicles
What causes the basilar membrane to vibrate at the same frequency of the sound?
In the inner ear, impact of the stapes on oval window
Describe high frequency and maximum vibration
High frequency (short wavelength) sounds cause the maximum vibration of basilar membrane closest to oval window
Describe low frequency and maximum vibration
Low frequency (long wavelength) sounds cause the maximum vibration of the basilar membrane farthest away from the oval window
Describe hair cells
Each hair cell is composed is composed of a distinct arrangement of shorter stereocilia (not true cilia) that increase in length.
Each stereocilia is connected to another at the top by an extracellular filamentous protein called tip link
What is the kinocilium?
Single true cilium during development that degenerates at birth
Tallest of the “hairs” on the hair cell
What happens if, during transduction, the stereocilia are bent towards the kinocilium?
The hair cell depolarizes
What happens if, during transduction, the stereocilia move away from the kinocilium?
Hair cell hyperpolarizes
Bending the hair cells towards the kinocilium opens ___
Potassium channels that depolarize the cell
Due to composition of the endolymph, potassium enter the hair cells and causes it to depolarize. Calcium is also involved
Describe the process by which sound waves are transmitted in the ear and converted to action potentials
Sounds waves are funneled into the ear by external ear
The middle ear ossicles are required to generate enough force to cause the water-filled cochlea to vibrate at the frequency of the sound (impendance matching)
In the cochlea, the vibration of the basilar membrane is determined by frequency of sound
High frequency sounds are near base of basilar membrane
Low frequency sounds are at the tip
Vibration causes bending of the hair cells
Depolarization of the hair cells is produced by influx of potassium and probably calcium
What does the ventral path do?
Starts processing of temporal and spectral features of sound
What does the dorsal path do?
Integrates the acoustic information with somatosensory information for localizing sound
What does the medial superior olive do?
Generates a map of intraaural time differences (how the sound arrived at the two ears differently)
What does the lateral superior olive do?
Generate a map of the intra-aural intensity differences
What does the inferior colliculus do?
Suppresses information related to echoes (they interfere with location) and arrives at a final estimation of the sound location on the horizon
What does the superior colliculus do?
Takes the location data from inferior colliculus and adds the third dimension (vertical height) to create a spatial map of the sound’s location
In the primary auditory cortex (A1), what are the rostral and caudal areas activated by?
More rostral areas are activated by low frequency sounds
More caudal areas receive information about high frequency sounds
