A variety of environmental stressors, such as temperature (hot and cold), infection, natural enemies, and starvation, can threaten life. To survive environmental stresses, mammals exert autonomic and behavioral responses as fundamental functions mediated by the CNS. Remarkable progress has recently been made in understanding the central circuit mechanisms of physiological responses to such stressors. A “trunk” neural pathway from the dorsomedial hypothalamus (DMH) to the rostral medullary raphe region (rMR) regulates sympathetic outflows to effector organs for homeostasis. Thermal and infection stress inputs to the preoptic area of the hypothalamus dynamically alter the DMH→rMR transmission to elicit thermoregulatory, febrile, and cardiovascular responses. Psychological stress signaling from the prefrontal cortex to the DMH drives sympathetic and behavioral responses for stress coping, representing a psychosomatic connection from the corticolimbic emotion circuit to the autonomic and somatic motor systems. Under starvation stress, medullary reticular neurons activated by hunger signaling from the hypothalamus suppress thermogenic drive from the rMR for energy saving and prime mastication to promote food intake. I will present a unified neural network for environmental stress responses, which provides novel insights into the integrative central regulation of organ functions that enables mammals to inhabit diverse environments on earth.