Effects of Microgravity on Human Physiology

Abstract

Physiology under extreme conditions reveals reactions of the human body, which may develop our knowledge of limits for a healthy individual. It may also help us to recognize premonitory signs of disease. Human physiology under microgravity (MG) is no exception. In April 1961, since Yuri Gagarin's first flight into space, it had become obvious that the environment of aerospace influences the human body in many ways. Even though humans can adapt to space, it can lead to problems when we return to Earth's gravity. The adaptation of humans can remain productive up to 1 year or longer. Many of the fundamental problems of aerospace medicine such as response to high altitudes, thermal support, dysbarism, hypoxia have been studied a long time before the human traveling aerospace by aviation and diving medicine. Aerospace, aviation, and diving medicine all involve operational changes, pressure excursions in body attitude and position, monitored breathing sources, and vital dependence on supportive mechanisms and life support equipment [1,2]. However, aerospace flight causes unique medical challenges. There was prolonged exposure to stressful stimuli such as acceleration forces, radiation, and MG. In particular, MG is a critical feature of aerospace flight. To appreciate the uniqueness of aerospace conditions, we should consider that the protective atmosphere and the static gravitational field of 9.81 m/s 2 are major factors that made Earth amenable to life. Gravity force is a more or less stable factor of the environment. Since the dawn of life, thus, it has influenced the phylogenetic development of all organisms [3]. Gravity has been a major contributor to the evolution of Earth's organisms from the aquatic life to the terrestrial one. By forcing ancestral organisms to adapt to the new environment, the complex system for gravity sensing, fluid regulation, stability, and locomo-