Previously, explorers, navigators and conquerors of the impossible have traveled incredible distances across seas and oceans, propelled by their technical advances. Therefore, the untapped and unexplored land of civilization “disappeared” from the face of the globe.
Today, astronauts fly in space and spend six months in Earth orbit aboard the International Space Station, virtually devoid of gravity. Tomorrow, space trips to the Moon or Mars could last several years. Big changes for the human body.
In fact, environmental changes in space are very important and permanently modify the performance of organisms that have, until then, slowly evolved to adapt to environmental changes, such as their environment or climate. “Space biology” applies to understanding the phenomena caused by changes in the living environment of space explorers, and support is necessary to better control their consequences for our astronauts’ organisms.
Bodies without attraction
Gravity has shaped the animal and plant world for millions of years. If it was not present, then we would not need such a complex cardiovascular system. For example, a protective mechanism that allows us to maintain normal cerebral circulation when we rapidly change position (lying on a stand in particular) is associated with the presence of gravity. It’Orthotics. It’s the same for bones and muscle systems, which adapt to gravity, because we spend most of our lives fighting gravity.
All physiological functions are covered in space medicine. Some of them are especially important to the well-being and performance of astronauts, as they require adaptation to the space environment. For example, these are the cardiovascular system, the musculoskeletal system, the sensory nervous system, nutrition and energy, radiation biology, and psychology. All this research in space biology has applications in everyday medicine.
Circulation has been at the heart of studies since Leica
The absence of gravity, as well as the confinement and cosmic rays, have implications for cardiovascular regulation.
Since the beginning of the space invasion, we’ve had to study whether the heart and vessels support a journey in microgravity. Thus, the blood pressure and heart rate of a Laika dog were monitored throughout their journey in 1957. These measurements showed that the cardiovascular system can adapt relatively well and paradoxically to this environment, since the limitations imposed on it are actually weaker than on Earth.
Upon return to Earth, the cardiovascular system becomes mismatched with gravity. Then prof Cardiovascular insufficiency syndrome, Due to physical inactivity and fluid transport caused by microgravity. Failure to adapt syndrome, which can be rapidly reversed after returning to Earth, was described as early as 1945 in another context, by A. Keys, in patients who have been bedridden for a long time.
Who needs a satellite gym
The musculoskeletal system allows us to walk and run “against gravity”, with specific perception of movement and direction. It was formed by constant gravity on Earth (worth 1 gram), but it is clearly very difficult to conduct experiments that change the value or direction of the gravitational field … except by going into space (or on an equivalent flight, but the experiment is much shorter).
So testing of individuals who live in modified gravity makes it possible to study the specific role of gravity on bone tissue in particular. Indeed, the absence of gravity alters its mass, structure, resistance, and time to recover. Longer than the duration of the task.
Exposure to microgravity during spaceflight also causes spatial disorientation, changes in body pattern, impairment of arm movement and precision gestures. These changes are due to the lack of a gravity frame of reference to provide AutolethysSmall crystals in the inner ear, which move when the head moves and thus modulate the deep sensation signals, but which are disrupted in the absence of gravity. In space, astronauts show a preference for visual information.
Read also: What if gravity disappeared …
Spaceflight also leads to a drastic drop in physical activity, which leads May lead The development of metabolic disorders, such asInsulin resistance Or dyslipidemia. Their role is increasingly evident in diseases associated with a sedentary lifestyle on Earth: obesity, diabetes, high blood pressure, or as a psychiatric risk factor.
Watch out for cosmic rays! What sunscreen for astronauts?
Exposure to ionizing radiation is one of the major components of the risk associated with space exploration. The radiation sources are well defined: solar and galactic radiation are added to the radiation inside the vessel, as it does not benefit from the protection of the geomagnet. On the other hand, the biological risks associated with prolonged exposure to these radiations remain difficult to assess.
Indeed, exposure to space radiation poses complex questions of scientific, medical and societal importance that are mostly identical to those posed by radiological diagnosis. This is especially the case The risk of developing cancers caused by radiationThe phenomenon of hypersensitivity to low doses of radiation, the effects of repeated doses and Individual susceptibility to radiation Radiation that causes cellular transitions.
Psychology and Socialization: Humans are Beyond Their Mechanisms
The trip to Mars is expected to take more than 500 days. This new dimension of space and time must be taken into account in future projects, with reference to the concept of “small self-organized firms”. During interplanetary missions, crews must be completely autonomous. In particular, a life support system (recycling water, oxygen, and carbon dioxide) can have an impact on behavior over time.
In addition, the prospects for interplanetary missions to the Moon or Mars direct research toward new psychological factors, such as isolation, confinement and monotony, and new social factors, such as gender, culture, and group.
Countermeasures, the key to health in space
Since the first spaceflight, international space agencies have become aware of many negative impacts of the environment on astronauts’ bodies. Space cannot be invaded without keeping astronauts healthy in order to ensure their survival and mission success. This is how protocols have been developed to prevent these physiological changes, which are called “countermeasures”. As the Mars programs enter the exploration phase, which will impose flights for two or three years, it is evolving Optimal Protocols for Preserving Astronauts’ Health It becomes a top priority.
Current countermeasures are mainly physical exercises, dietary measures or over the counter medications. Recently, vibration, electrical stimulation, or even centrifugation have also been developed. These countermeasures are generally recommended to treat people with, for example, osteoporosis, kidney failure, arterial and venous damage, sarcopenia, or insulin resistance. They were first tested on the ground in trials of prolonged bed rest.
An unstable lifestyle, a public health problem in the twenty-first century in space … and on Earth
Although space is a unique environment, there are clear similarities between spaceflight, aging and immobility, but also for us on Earth to minimize the harmful effects of inactivity on public health. Who long ago Classified sedentary lifestyle It is among the top ten causes of death and disability worldwide.
The beginning of the third millennium will witness a doubling of exploration projects for the solar system. Unlike boats that have sailed into the oceans with their crews, the new ships that cross the interplanetary space are not currently inhabited by humans but robots, which makes missions less restrictive.
Head of Life Sciences at CNES, National Center for Space Studies (CNES)
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