cardiovascular system adapts to space. Now we're looking forward to their first day back! They've adapted well to space, but now they will have to readjust to 1g, which will have dramatic effects on the cardiovascular system.''
Still other investigations focused on the response of the kidneys and endocrine glands to the microgravity environment and their ability to control hormones that regulate blood volume, pressure and essential electrolytes. During SLS-1, these renal/endocrine and haematology studies examined plasma (the fluid component of our blood) and red blood cells. The plasma experiments allowed scientists to identify the types of nutrients circulating throughout the body to determine whether or not the astronauts were well nourished and well hydrated. One notable observation was the decrease in red blood cell production, which it was realised could complicate inflight illnesses or injuries on long-duration missions.
On Earth, gravity affects bodily fluids by pulling them towards our feet, but in space they are redistributed to the head and torso, which causes changes in the kidneys and fluid-regulating hormones in the cardiovascular and blood systems. During SLS-2, experimenters investigated the theory that the kidneys and endocrine glands adjust the body's fluid-regulating hormones to stimulate an increase in fluid to be excreted. Over longer periods of time, the kidneys and hormones establish new levels of salts, minerals and hormones appropriate for the reduced fluid volume. The plasma shift also affects the blood system through decreases in plasma volume.
In order to determine immediate and long-term changes in their kidney functions, water, salt and mineral balance and fluid shifts, Columbia's astronauts collected urine samples throughout the mission. Additionally, they carefully measured their body weight daily and logged all food, fluids and medication taken while in space. Chemical tracers were also injected into the rats to measure changes in their red blood cell and plasma volumes.
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