16. Vertebrate Responses to Spaceflight

As man sought to travel from the terrestrial environment, he could bring with him many things necessary for survival, but he could not bring the Earth’s gravitational field. It was expected that organisms removed from their normal ambient force environment would exhibit changes in physiology and behavior as they adapted to their new environment. Changes were expected in the “anti-gravity” systems; those designed to hold us up, move us around and circulate our fluids. And such proved to be the case. However, the multitude of spaceflight experiments conducted to date have revealed that the gravitational environment affects many systems that, at first glance, appear to have no connection to the ambient force environment. These experiments have become more detailed and comprehensive as the machinery allowing us access to space has become more sophisticated. Results from such studies are useful, not only in the design of countermeasures used to ensure astronaut health and safety, but also as they increase our understanding of the role the ambient force environment plays in the normative physiology of organisms here on Earth.