How Weightlessness Affects the Human Body
While modern techniques are able to dispel most of the concerns of the vacuum, the affects of space travel on the human body are still apparent within a protected environment. Weightlessness is the largest influence on the human body, causing a number of problems.
Spacesickness is one of the most common side effects of space travel on the human body. Due to the fact that there is no constant source of gravity in space, individuals begin to experience unfamiliar effects. A portion of the middle ear known as the otolith is responsible for keeping a person's equilibrium constant while on Earth. In space, this organ becomes confused and stops providing the body with necessary adjustments to muscles and vision that keep people stable. Essentially, there is no real reason for muscles to contract and the brain cannot determine which way is up. Motion sickness can impact people for a number of days.
The microgravity environment of space also impacts the dispersal of fluids within a human body. In only a few minutes of exposure, the fluids in the body swell up in the upper body. This causes symptoms such as a puffy face and bulging veins. The longer the duration of space travel, the worse the effects become. Ultimately, people returning to Earth will experience problems standing and an increased chance of fainting due to the fact that plasma levels drop and a person's natural blood regulation is altered.
One of the most dramatic effects of space travel on the human body is the fact that skeletal and muscular systems lose cohesion over time. The longer a person spends in space, the less important the human skeleton and muscles become. Since these systems only exist to provide weight bearing support while in a gravitational environment, there is little need for their existence in space. According to studies conducted by the Russian Space Agency, NASA and other space agencies, muscular atrophy occurs almost immediately and bone tissue loss proceeds at a rate of 1.5 percent per month. The only way to combat these problems is through exercise and a controlled diet.
Modern developments in space suit technology and controlled environments have made the threats of the vacuum of space unlikely events. However, as humans continue to send people into space, the chances of accidents will continue. Also, studies will continue into combating the side effects of weightlessness. As humans continue the exploration of the stars, new effects of space travel on the human body will most likely be discovered.
Above left: Weightlessness. (Supplied by NASA; Public Domain; http://upload.wikimedia.org/wikipedia/commons/c/c4/Foale_ZeroG.jpg)