The human body is an organized set of systems. These systems are designed to function on Earth. In orbit, where the pull of gravity is not felt, the systems may not function the way they do on Earth. There are many physical symptoms^* experienced by astronauts in orbit.(28.8K) (56.7) (download) The human body takes on a new appearance in orbit.

Some other effects of space flight include:

• Space Adaptation Syndrome
• Space anemia^*
• Calcium loss
• Changes in perception^*

There are also mental considerations. NASA is concerned with how astronauts mentally deal with living in space. And of course there is the re-adjustment to gravity after a space mission is over.