Homeostasis is defined as the ability of a cell or system of cells to detect a perturbation and, in the continued presence of that perturbation, generate a compensatory response that precisely restores baseline function. Evolutionarily conserved homeostatic signaling systems stabilize the function of individual neurons and neural circuitry in organisms that range from insects to human. Our goal is to delineate these homeostatic signaling systems in cellular and molecular detail and define how they succeed or fail in health and disease. 

TOP: Each neuronal cell type has cell type-specific firing properties that are determined by the balance of excitatory and inhibitory synaptic inputs as well as the ion channels that the neuron expresses (red and blue ovals). In response to a perturbation (arrow) a neuron can adjust synaptic drive and ion channel expression to re-establish normal baseline firing properties. This is the definition of homeostatic control of neural function. 

BOTTOM: Neurotransmission is controlled by homeostatic signaling. At the neuromuscular junction (shown), the release of synaptic vesicles depolarized the postsynaptic cell. In response to impaired postsynaptic neurotransmitter receptor sensitivity, a homeostatic signaling system causes more vesicles to be released. This effect precisely offsets the magnitude of the postsynaptic perturbation. This effect can be induced in seconds to minutes and can be sustained for the life of an organism. This form of homeostatic control is evolutionarily conserved from fly to human, implying an ancient and fundamental role in stabilizing the synaptic communication of information throughout the nervous system.