2007 Sensory Physiology

Transduction channels

  • the apical ends of stereocilia in adjacent rows are connected by tip links
  • positive stereocilia deflection increases the tension in the tip link which directly causes the transduction channels found at the ends of the tip links to open (i.e., no second messengers)
  • mechanotransduction channels are non-selective - the endolymph in the scala media contains 150 mM K+ - opening the transduction channel causes K+ to flow IN to the hair cell (since the intracellular [K+] is only 120 mM and the electrical gradient favours cation entry) and the K+ current depolarizes the hair cell
  • the resting membrane potential of hair cells is slightly depolarized (compared to a "normal" nerve cell), as there is a tendency for some transduction channels to be open - this allows negative deflection to cause hyperpolarization by closing the channels that are open at rest
Tip link
Transduction current

 

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