ABSTRACT

The cardiovascular, vestibular and musculoskeletal systems are disturbed during a space flight. Because gravity plays a determining role in their functional activity on Earth, the changes observed in weightlessness are therefore not surprising. However, the influence of weightlessness does not limit itself to the above three systems. Indeed, the redistribution of the blood mass created by weightlessness and the resulting changes in blood circulation could have repercussions on organs the activity of which is considered gravity independent. Other reactions occurring during space flights might therefore be linked not to a direct but to indirect effects of weightlessness. However, caution should be exercised before making such connections because the mechanisms causing the appearance of these responses remain unknown.