Effects on the Human Body in Space
What effect does gravity have on the human body and what happens in the absence of gravity?
The human body has developed in such a way that it depends upon Earth’s gravity for many functions. These functions are blood flow or circulation, balance and equilibrium, and bone & muscle health. In the absence of gravity, these functions or systems do not operate as efficiently and over time, they may fail entirely.
Primary among these functions is to assist the heart in pumping blood throughout the entire body. The force of gravity ensures that blood is flowing to the lower extremities. In a zero gravity atmosphere, the heart still pumps the excess blood that will no longer reach the legs and can cause an inflated look of a person’s upper torso and face. This effect may cause “space sickness” in humans, which causes headaches and nausea. These effects usually cease once the body adapts to the changes.
Another function that gravity assists with is a balance and equilibrium. While grounded on Earth, a human maintains their balance through the functions of the inner ear however, this organ does not function properly without gravity which causes physical disorientation and may also lead to psychological disorientation over time. Psychological disorientation occurs commonly due to a lack of visual cues that humans use in their normal environment such as the horizon, the directional orientation of things in nature, and man-made structures as well. Over time, the mind and body develop new methods for finding balance.
Finally, the human body relies upon gravity to ensure proper use and health of their muscles and skeletal frame. On Earth, in the presence of gravity, humans benefit from the resistance and pressure of gravity to keep muscles active and bones in good health. The lack of gravity in outer-space removes the natural resistance and pressure which severely reduces muscle use, this causes muscles to...