L12 The Auditory System Flashcards
External Ear
- The cartilaginous pinna (___________) directs sound waves into the external auditory canal (_____________)
- The outer canal is bordered by ______, but the inner borders are _____
- The canal ends at the ______________.
External Ear
- The cartilaginous pinna (or Auricle) directs sound waves into the external auditory canal (or Meatus)
- The outer canal is bordered by cartilage, but the inner borders are bony
- The canal ends at the tympanic membrane
What is the role of the inner ear? What contributes to this and in what proportion?
Impedance Matching (efficiently transferring waves from air to water)
- Most impedance matching results from the size difference in the tympanic membrane and the oval window (17-20 fold difference). As pressure = force/area, applying the same force over a smaller area increases the pressure.
- Lever action of the ossicles also contributes to impedance matching (30-35% increase)
Muscles of the inner ear and their innervation? What reflex are they responsible for?
The bony labyrinth is a space within the ____________________. This space is filled with ___________ (composition similar to CSF)
The bony labyrinth is a space within the petrous part of the temporal bone. This space is filled with perilymph (composition similar to CSF)
Within the bony labyrinth is the _______________. This is filled with __________ (high K +). All sensory cells in the inner ear are found within.
Within the bony labythinth is the membranous labyrinth. This is filled with endolymph (high K ++). All sensory cells in the inner ear are found within the membranous labyrinth.
The conical central axis of spongy bone within the cochlea is called the _______________
The conical central axis of spongy bone within the cochlea is called the Modioulus
The ______________________ is part of the membranous labyrinth and contains ________________ => therefore hair cells in the _____________ have a higher normal resting membrane potential (?mV)
The Scala Media is part of the membranous labyrinth and contains endolymph (high K ++) => therefore hair cells in the Organ of Corti have a higher normal resting membrane potential (-45–50 mV)
_____________ starts at the oval window and is continuous with the ______________, which terminates at the round window.
Scala Vestibuli starts at the oval window and is continuous with the Scala Tympani, which terminates at the round window.
What is Von Bekesy’s place principle?
Sound of different frequencies cause vibrations at different points in the basilar membrane:
- Frequency is encoded into position along the membrane
- Amplitude is encoded by degree of activation along the membrane
Deflection of the basilar membrane results in movement of the __________________. Inner hair cells project into the ______________. As the structure moves, this causes deflection of the _______ of these hair cells, which is where neural signals are generated in the auditory system.
Deflection of the basilar membrane results in movement of the Organ of Corti. Inner hair cells project into the Tectorial Membrane. As the structure moves, this causes deflection of the Stereocilia of these hair cells, which is where neural signals are generated in the auditory system.
Directionality of Streocillia and Kinocillium within the Organ of Corti?
Force applied in DIRECTION of Kincocilium => DEPOLARIZATION and release of more neurotransmitters
Force applied in OPPOSITE DIRECTION of Kinicilium => HYPERPOLARIZATION and release of less neurotransmitter
Inner vs. Outer Hair Cells?
Inner Hair Cells: Project into the Tectorial Membrane. As the structure moves, this causes deflection of the Stereocilia of these hair cells, which is where neural signals are generated in the auditory system.
Outer Hair Cells: Either enhance or suppress the movement of the Organ of Corti. They are activated in response to sound, and because they cause movement of the membranes, outer hair cells can generate sound (otoacoustic emissions) in response to sound. This can be measured (otoacoustic emission testing), which is the basis of newborn auditory screening programs.
What is the basis of newborn auditory screening programs? What is this testing called?
Outer Hair Cells either enhance or suppress the movement of the Organ of Corti. They are activated in response to sound, and because they cause movement of the membranes, outer hair cells can generate sound (Otoacoustic Emissions) in response to sound. This can be measured (Otoacoustic Emission Testing), which is the basis of newborn auditory screening programs.
Auditory Pathways
________________________from the Inner/Outer Hair Cells project to:
- ____________________________
- ____________________________
- ____________________________
- ____________________________
- ____________________________
NOTE: Each side of cortex receives input from both sides, 4 neurons in the pathway versus the usual 3
Projections also go to the __________________(Alertness/Arousal)
Spiral Ganglion Cells from the Inner/Outer Hair Cells project to:
- Cochlear Nucelus
- Superior Olivary Nucleus
- Inferior Colliculus
- Medial Geniculate of Thalamus
- Primary Auditory Cortex
NOTE: Each side of cortex receives input from both sides, 4 neurons in the pathway versus the usual 3
Projections also go to Brainstem Reticular Nuclei (Alertness/Arousal)
- Information from the cochlear hair cells is passed to the _______________
- Projections are Bilateral to the ______________ (How is Latency Controlled?)
- ________________ detects INTENSITY differences between both sides while the ______________ detects TIMING Differences
- Inferior Colliculus also has a projection to the Superior Colliculus (What is this Important for?)
- Information from the cochlear hair cells is passed to the Cochlear Nucleus
- Projections are Bilateral to the Superior Olive (Latency of these projections is precisely controlled by regulating the myelin sheath to ensure signal arrives on both sides at the same time)
- Lateral Superior Olive detects INTENSITY differences between both sides while the Medial Superior Olive detects TIMING Differences
- Inferior Colliculus also has a projection to the Superior Colliculus (Important for integrating visual and auditory signals (Multimodal Sensory Perception))
