3.5.2 Mechanical force directly opens and closes transduction channels
It is believed that tip links aid in causing ‘channels’ to open and close near the top of the hair cell (Figure 16). Tip links are filamentous connections between two stereocilia. Each tip link is a fine fibre obliquely joining the distal end of one stereocilium to the side of the longest adjacent process. It is thought that each link is attached at one end or both to the molecular gates of one or a few channels. Under this arrangement, pushing a bundle in one direction increases the tension on the tip link and promotes channel opening while pushing the bundle in the opposite direction slackens the link and the associated channel closes.
Figure 16 Mechanism of mechano-electrical transduction. When the hair bundle is at rest each transduction channel oscillates between closed and open states, spending most of the time closed. Displacement of the bundle in the positive direction increases tension on the tip link and promotes channel opening, the influx of cations and a depolarizing receptor potential