function of the auditory and vestibular systems

• What is the maximum firing frequency of neurons related to phase locking?

  1 kHz
• How does the volley principle affect phase locking?

  It increases the range of phase locking up to 4 kHz.
• What happens to auditory nerve impulses at higher frequencies?

  They are not phase locked.
• What does tonotopy resolve in auditory processing?

  It resolves intermediate and higher frequencies.
• What does a tonotopic map provide in auditory analysis?

  A structural analysis over a range of frequencies.
• How does frequency analysis extend up to 4 kHz?

  Through additional frequency analysis mechanisms.
• How is frequency distinguishability maintained in the auditory cortex?

  Different parts of the cortex respond to different frequencies.
• What mechanisms are involved in sound processing up to 1 kHz?

  Phase locking and some tonotopy.
• What mechanisms are involved in sound processing between 1 kHz and 4 kHz?

  Phase locking with the volley principle and tonotopy.
• What mechanisms are involved in sound processing above 4 kHz?

  Tonotopy only.
• How does the cochlea enhance frequency responses?

  By having a basilar membrane amplitude enhanced over 100 times.
• What effect do drugs like salicylate and furosemide have on the cochlea?

  They affect the sharpness of frequency responses.
• What is the role of outer hair cells in the cochlear amplifier?

  They are active and amplify basilar membrane movement.
• What happens when outer hair cells depolarize?

  Prestin, a motor protein, is activated, inducing contraction.
• How much do outer hair cells contract when activated?

  About 100 nm.
• What is the significance of otoacoustic emissions?

  They provide evidence for active mechanisms in hearing.
• What do high spontaneous rate fibers do in response to sound levels?

  They are easily excited at low sound levels but soon saturate.
• What do medium spontaneous rate fibers do in response to sound levels?

  They are excited at medium sound levels and will saturate.
• What do low spontaneous rate fibers do in response to sound levels?

  They are excited when sound levels are high and can detect changes at very high levels.
• How is loudness detected in the auditory system?

  By the population of afferent nerves.
• What is the role of the vestibular system?

  It monitors the position and movement of the head and contributes to balance.
• What disorders can arise from vestibular system dysfunction?

  Vertigo, nausea, and uncontrollable eye movement.
• What are the two types of otolithic organs?

  Saccule and utricle.
• What do otolithic organs detect?

  Gravity, tilt of the head, and linear acceleration.
• What is the main difference between vestibular and cochlear hair cells?

  Vestibular hair cells have kinocilium, while cochlear hair cells do not.
• How do vestibular hair cells transduce mechanical signals?

  Through mechanotransducer channels and stereocilia in endolymph.
• What happens when stereocilia are displaced towards the kinocilium?

  Depolarization occurs.
• What happens when stereocilia are displaced away from the kinocilium?

  Hyperpolarization occurs.
• How does head movement affect hair cell activation?

  It causes force on otoliths, moving the cap and deflecting stereocilia.
• How are hair cells oriented in the utricle and saccule?

  They are oriented to transduce all movements, with a mirror image arrangement.
• What is the role of the semicircular canals?

  They detect angular (rotational) acceleration.
• How does endolymph affect hair cell activation in semicircular canals?

  Its inertia bends the cupula in the direction of the endolymph.
• What is the significance of push-pull activation in the vestibular system?

  It allows for coordinated responses to head movements.
• What do central vestibular connections coordinate?

  They integrate information from vestibular and other systems.
• What is the role of vestibular reflexes?

  They project information to control motor neurons for head and body position.
• What is the vestibulo-ocular reflex?

  It produces compensatory eye movements to fix a visual target.
• How do the left and right canals interact during the vestibulo-ocular reflex?

  The left canal is stimulatory while the right canal is inhibitory.
• What do the combined responses of extraocular muscles produce?

  Simultaneous, rapid, and accurate eye movements.