The Effects of Zero Gravity & Space Travel on Body Systems

Traveling beyond Earth's atmosphere poses a serious challenge to the human body. The body's systems evolved to rely on Earth's gravity and atmosphere to function properly. Away from Earth, the body must cope with an entirely new environment that can cause extreme discomfort for the astronaut. Astronauts who are spending time in zero gravity need to take precautions to avoid suffering long-lasting ill effects.

Circulation

• On Earth, the heart depends on gravity to help pump blood to the lower extremities. This allows the heart to more efficiently pump blood to the upper body. In space, gravity no longer guides blood down to the legs, so the astronaut's legs may become thinner by being deprived of blood. Since the heart is still pumping excess blood to the upper body to compensate for Earth's gravity, the face, torso and arms may exhibit an inflated appearance. This distribution of blood may cause "space sickness," a condition marked by headaches and nausea. Space sickness is usually not dangerous and wears off after the body has had time to adapt to zero gravity.

Bones & Muscle

• Without the resistance of gravity or the need to walk, the body's muscles become atrophied in space because they are not used as much. Bones undergo a similar process of atrophy, becoming weaker due to a lack of nutrients. This loss of bone tissue is especially severe in the lower body. Astronauts can slow the atrophy process through rigorous exercise and taking dietary supplements to keep muscle mass and prevent the bones from wasting away.

Balance

• An astronaut's sense of direction can be severely affected by zero gravity. The primary organ involved in balance is the inner ear, which cannot function properly without gravity. According to the NASA website scence.nasa.gov, life in space can cause psychological disorientation as well, since the brain depends upon visual cues to keep the body balanced. Earth-dependent points of reference such as the horizon are missing, forcing the brain to develop a new frame of reference to maintain balance.