Fluid redistribution Effect of spaceflight on the human body
the effects of microgravity on fluid distribution around body (greatly exaggerated).
astronaut clayton anderson observes water bubble floats in front of him on discovery. water cohesion plays bigger role in microgravity on earth
the second effect of weightlessness takes place in human fluids. body made of 60% water, of intra-vascular , inter-cellular. within few moments of entering microgravity environment, fluid re-distributed upper body resulting in bulging neck veins, puffy face , sinus , nasal congestion can last throughout duration of trip , symptoms of common cold. in space autonomic reactions of body maintain blood pressure not required , fluid distributed more around whole body. results in decrease in plasma volume of around 20%. these fluid shifts initiate cascade of adaptive systemic effects can dangerous upon return earth. orthostatic intolerance results in astronauts returning earth after extended space missions being unable stand unassisted more 10 minutes @ time without fainting. due in part changes in autonomic regulation of blood pressure , loss of plasma volume. although effect becomes worse longer time spent in space, yet individuals have returned normal within @ few weeks of landing.
in space, astronauts lose fluid volume—including 22% of blood volume. because has less blood pump, heart atrophy. weakened heart results in low blood pressure , can produce problem orthostatic tolerance , or body s ability send enough oxygen brain without astronaut s fainting or becoming dizzy. under effects of earth s gravity, blood , other body fluids pulled towards lower body. when gravity taken away or reduced during space exploration, blood tends collect in upper body instead, resulting in facial edema , other unwelcome side effects. upon return earth, blood begins pool in lower extremities again, resulting in orthostatic hypotension.
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