Abstract
The ears of all vertebrate species use sensory hair cells (Fig. 3.1) to convert mechanical energy to electrical signals compatible with the nervous system. However, although the basic structure of hair cells is ubiquitous among the vertebrates and hair cells are also found in the lateral line of fishes and aquatic amphibians, a growing body of literature has demonstrated considerable heterogeneity in morphology and physiology in different taxa and even within different end organs of the same species. Although far less is known about the functional diversity that accompanies the differences in structure and physiology, it is increasingly likely that these differences reflect the ability to respond to different types of signals and/or to process signals in different ways before a neurotransmitter is released and a signal is sent to the brain.