Hearing relies on molecular tip links with no known repair mechanism

Evidence

Hair cells must respond more rapidly than any other sensory receptor cells in the body, and the single molecular strand tip links are the eye of the needle in the whole system. The vibrations of the organ of Corti and the consequent rocking-tilting motion of the hair cells yank on the tip link, which opens ion channel entrances to nerve cells mechanically in real time. The tip link pulls like a chain on a sink drain, and in the ions go. In contrast, the eye takes much longer to respond to light stimulus. Every listening moment, we are dependent on a few thousand fantastically small single molecules whose job it is to open and close ion channels in the hair cells. If the hairs break, or if one of the tip links breaks or is yanked off one of the two cells it is attached to, there is no known repair mechanism. — Eric J. Heller, Why You Hear What You Hear- An…, 1955

Categorization

• DEFINE: Explains tip links, the molecular chain that opens ion channels mechanically.
• XREF: The irreparable tip links connect to age-related and noise-induced hearing loss, a theme likely in later chapters.