Figure 1.
The orbital motion of the lower boundary, the reticular lamina (the cuticular plate is part of the reticular lamina) and the vertical oscillatory motion of upper boundary (tectorial membrane) hydrodynamically drive the bundle. Three stepped rows of stereocilia (actin-filled rod structures) are connected by two sets of tip links with gating springs and six horizontal top connectors. Upper tip links connect the tallest and middle rows; lower tip links connect the shortest and middle rows. All elements are assumed to be elastic with bending and stretching energies. The fluid is viscous and incompressible.
Figure 2.
Tip link stretching as a function of phase of reticular lamina motion.
Upper panel: tectorial membrane in normal position, red-upper tip link; black- lower tip link. Lower panel; the tectorial membrane-reticular lamina spacing is widened by 5 microns; same color code. Molecular gate does not open when tip link is in compression (negative values of stretching). Model confirms the critical role of the tectorial membrane for hearing sensitivity.
Figure 3.
Motion of individual rows of stereocilia.
All rows undergo a length change and a rotation, except the middle row has a negligible rotation (see Video S1).
Figure 4.
A nanovortex forms near an open gate to augment supply of cations.
Closed vorticity contours imply the presence of a fluid eddy. Vorticity values are sec−1. Yellow lines show the locations of the stereocilia when the phase of the reticular lamina orbital motion is 214.6 degrees.