Lecture 9: Auditory Senses Flashcards
List the bones of the middle ear in order
Malleus, Incus, Stapes
Tensor tympani
Muscle that inserts on the malleus and pulls handle of malleus inward
Stapedius
Muscle that inserts on the stapes and pulls stapes outward
Attenuation reflex
Opposing forces of the tensor tympani and stapedius muscles that dampens sound; protects the cochlea and masks low frequency sounds in loud environements
How does the action of the tensor tympani and stapedius muscles affect a person’s sensitivity to her/her own speech?
Decreases sensitivity to own voice
What two structures are involved in impedance matching?
Tympanic membrane and ossicles
Why is impedance matching important?
Increases force from the ossicular system to cochlear fluid which is needed in order to cause vibration in the fluid
How is hearing affected in the absence of the ossicular system?
Sound still passes through the middle ear to cochlea, but sensitivity is decreased by 15-20 decibels
What are the major components of the cochlea?
Scala vestibuli, Scala media, Scala tympani, Reissner’s membrane
What is the function of Reissner’s membrane?
Separates scala media from scala vestibuli, maintaining special fluid (endolymph) within scala media
Basilar membrane
Separates scala media from scala tympani; contains fibers that have the ability to vibrate
How does the length and diameter of basilar fibers differ from the oval window to the apex of the cochlea?
A. Length and diameter increase from oval window to apex
B. Length and diameter decrease from oval window to apex
C. Length decreases from oval window to apex, while diameter increases
D. Length increases from oval window to apex, while diameter decreases
D. Length increases from oval window to apex, while diameter decreases
What are the characteristics of fibers near the oval window and at what frequencies do they vibrate?
Stiff, short fibers; beat at high frequency
What are the characteristics of fibers near the apex of the cochlea and at what frequencies do they vibrate?
Long, limber fibers; beat at low frequency
What are the sensory receptors of the organ of Corti?
Hair cells
What creates the mechanical transduction leading to the depolarization of the hair cell membrane?
Tensile force created on shorter cilia when they are bent in the direction of longer sterocilia
Where is endolymph located and what is its ionic composition?
Scala media; high [K+], low [Na+]
Where is perilymph located and what is its ionic composition?
Scala vestibuli and scala tympani; Low [K+], high [Na+]
What is the endocochlear potential?
+80 mV difference between endolymph and perilymph
Place principle
Nervous system detects sound frequencies by determining positions along the basilar membrane that are most stimulated
How does the frequency range that can be heard change with age?
Frequency is shortened; age related hearing loss usually in high frequency sound
Where does decussation occur between the right and left auditory pathways?
Brainstem/pons
What is the difference between the primary auditory cortex and association areas?
Auditory cortex directly excited by projections from medial geniculate body; association areas are secondarily excited by impulses from auditory cortex
