Organisms have developed remarkable specializations to sense and navigate their environments. Fish are able to detect predators and prey using a network of mechanosensory hair cells, called the lateral line, that are located on the surface of the skin. These cells detect disruptions in their surrounding fluid and convert mechanical information to electrical impulses that are relayed to the brain. The mechanosensory hair cells of the lateral line are both structurally and functionally similar to those of the inner ear that mediate hearing and balance. While hair cells of the inner ear are encased in the bony cochlea and therefore difficult to access, lateral line hair cells of the larval zebrafish can be easily visualized, mechanically stimulated and genetically manipulated providing an opportunity to learn general principles about hair cell function. Using the larval zebrafish lateral line, Joy applies in vivo functional imaging, electrophysiological and molecular biology approaches to visualize hair cell responses to mechanical input at the organelle and synaptic level. Joy will present work showing how hair cell mitochondria respond to both acute and long-term mechanical stimulation and will show that hair cells express excitatory neurotransmitter receptors, NMDA receptors, that can both protect against and promote cellular damage. The cellular adaptations that protect mechanosensory cells limit ionic, particularly Ca2+, imbalances that lead to cell death. These studies of cytoplasmic and mitochondrial Ca2+ homeostasis may have implications for organisms living in osmotically imbalanced and metabolically demanding environments.