Bell Andrew
Research School of Biological Sciences, The Australian National University, Canberra, ACT 0200, Australia.
J Biosci. 2007 Mar;32(2):385-404. doi: 10.1007/s12038-007-0037-9.
It is widely thought that organisms detect sound by sensing the deflection of hair-like projections, the stereocilia, at the apex of hair cells. In the case of mammals, the standard interpretation is that hair cells in the cochlea respond to deflection of stereocilia induced by motion generated by a hydrodynamic travelling wave. But in the light of persistent anomalies, an alternative hypothesis seems to have some merit: that sensing cells (in particular the outer hair cells) may, at least at low intensities, be reacting to a different stimulus - the rapid pressure wave that sweeps through the cochlear fluids at the speed of sound in water. This would explain why fast responses are sometimes seen before the peak of the travelling wave. Yet how could cells directly sense fluid pressure? Here, a model is constructed of the outer hair cell as a pressure vessel able to sense pressure variations across its cuticular pore, and this 'fontanelle' model, based on the sensing action of the basal body at this compliant spot, could explain the observed anomalies. Moreover, the fontanelle model can be applied to a wide range of other organisms, suggesting that direct pressure detection is a general mode of sensing complementary to stereociliar displacement.
人们普遍认为，生物体通过感知毛细胞顶端毛发状突起（即静纤毛）的偏转来检测声音。对于哺乳动物而言，标准的解释是，耳蜗中的毛细胞对由水动力行波产生的运动引起的静纤毛偏转作出反应。但鉴于持续存在的异常情况，另一种假设似乎有一定道理：传感细胞（特别是外毛细胞），至少在低强度下，可能对不同的刺激作出反应——以水中声速扫过耳蜗液的快速压力波。这可以解释为什么有时在行波峰值之前会出现快速反应。然而，细胞如何直接感知流体压力呢？在此，构建了一个外毛细胞模型，将其视为一个能够感知其表皮孔上压力变化的压力容器，基于基体在这个顺应性部位的传感作用，这个“囟门”模型可以解释观察到的异常现象。此外，囟门模型可以应用于广泛的其他生物体，这表明直接压力检测是一种与静纤毛位移互补的通用传感模式。
