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耳蜗放大器与基底膜频率调谐

时间:2024-07-03 百科知识 版权反馈
【摘要】:对听敏度保持较好的动物进行的实验表明,在蜗底BF附近,基底膜与听神经单纤维反应的调谐曲线非常相似,其反应阈值几乎一致。从理论上说,像耳蜗这样的频率调谐系统,其调谐的敏锐程度受限于黏性阻尼,如果向其加入一个动力,就有可能改善调谐的敏锐程度。动物实验和耳蜗机械模型的研究表明,耳蜗敏锐的频率调谐确实需要耳蜗放大器的电-机械反馈机制的存在。

对听敏度保持较好的动物进行的实验表明,在蜗底BF附近,基底膜与听神经单纤维反应的调谐曲线非常相似(图7-10),其反应阈值几乎一致。这表明,灵敏耳蜗本身就可有很敏锐的机械调谐,从而向听神经输送足够精细的调谐信号。从理论上说,像耳蜗这样的频率调谐系统,其调谐的敏锐程度受限于黏性阻尼,如果向其加入一个动力,就有可能改善调谐的敏锐程度。动物实验和耳蜗机械模型的研究表明,耳蜗敏锐的频率调谐确实需要耳蜗放大器的电-机械反馈机制的存在。但耳蜗机械模型的研究还提示,仅有单一的电-机械反馈还不足以产生足够好的频率调谐,为了恰到好处地抵消耳蜗内的流体动力学阻尼,还需要有一个滤波机制或者是其他的频率特异性机制同时起作用,由此,或以另一种不同于被动机制但也是按频率-距离分布的主动性共振机制(譬如通过盖膜、网状板、盖膜下淋巴液及纤毛之间的相互作用)调制向基底膜传输的主动性动力,或使电-机械反馈提供的动力在恰当的时间作用于基底膜的恰当位置。

图7-10 栗鼠耳蜗机械振动与听神经单纤维反应的频率调谐曲线的比较

(郑杰夫)

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