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Abstract(s)
Após mais de 60 anos de voos espaciais, estamos a começar a entender alguns dos mecanismos de adaptações fisiológicas do organismo humano ao ambiente espacial.
Ainda há um longo caminho a percorrer antes de podermos enviar o ser humano para Marte em segurança. Até lá, inúmeros estudos terão de ser realizados, em missões de curta e longa duração, de forma a avaliar corretamente a influência deste ambiente na fisiologia humana.
Quando a força gravitacional de 1G deixa de atuar sobre o organismo humano, alterações drásticas podem ocorrer. Algumas destas adaptações podem ser consideradas agudas, como a atrofia muscular, a perda de densidade óssea e o descondicionamento cardiovascular, e outras progressivas, como as resultantes do efeito da radiação e de alterações no balanço hídrico. No entanto, na generalidade dos casos, todas são reversíveis com o retornar à Terra, e consequentemente a uma força gravitacional de 1G.
Uma das principais alterações verificadas é a nível do sistema cardiovascular e resulta, principalmente, da redistribuição superior de fluidos. A acumulação de fluidos na metade superior do corpo está na origem de alterações no sistema nervoso autónomo, nomeadamente dos reflexos autonómicos, que por sua vez levam a alterações dos parâmetros cardíacos.
Estudos mais recentes têm demonstrado que, em situações mais crónicas, a microgravidade poderá estar na origem de arritmias cardíacas e atrofia do músculo cardíaco, o que tem vindo a preocupar cientistas e fisiologistas.
Nesta revisão, irão ser abordadas as principais modificações observadas no sistema cardiovascular, nos voos de curta e de longa duração, a forma como estas afetam a homestasia orgânica, e que contramedidas existem que possam atenuar estes mesmos efeitos.
After more than 60 years of spaceflights, we are beginning to understand some of the mechanisms of physiological adaptations of the human organism to space environment. There is still a long way to go before we can safely send humans to Mars. Until then, many studies in short and long duration missions will have to be carried out in order to properly assess the influence of this environment on human physiology. When the gravitational force ceases to act on the human organism, drastic adjustments can take place. Some of these adaptations are acute, such as muscular atrophy and deconditioning, loss of bone density, and cardiovascular deconditioning, and others more progressive, resulting from the effects of radiation and changes in water balance. In most cases, these changes are reversible when astronauts return to Earth. One of the main changes detected is in the cardiovascular system, and results mainly from fluid redistribution. The accumulation of fluids in the upper half of the body is responsible for deviations in the autonomic nervous system, specifically the autonomic reflexes, which, in turn, leads to changes in the cardiac parameters. Recently, studies have shown that, in more chronic situations, microgravity may be the cause of cardiac arrhythmias and cardiac atrophy, which has been worrying scientists and physiologists. In this review, we will discuss the main changes observed in the cardiovascular system, in short and long duration flights, the way that they affect the homeostasis and the existing countermeasures that can mitigate these same effects.
After more than 60 years of spaceflights, we are beginning to understand some of the mechanisms of physiological adaptations of the human organism to space environment. There is still a long way to go before we can safely send humans to Mars. Until then, many studies in short and long duration missions will have to be carried out in order to properly assess the influence of this environment on human physiology. When the gravitational force ceases to act on the human organism, drastic adjustments can take place. Some of these adaptations are acute, such as muscular atrophy and deconditioning, loss of bone density, and cardiovascular deconditioning, and others more progressive, resulting from the effects of radiation and changes in water balance. In most cases, these changes are reversible when astronauts return to Earth. One of the main changes detected is in the cardiovascular system, and results mainly from fluid redistribution. The accumulation of fluids in the upper half of the body is responsible for deviations in the autonomic nervous system, specifically the autonomic reflexes, which, in turn, leads to changes in the cardiac parameters. Recently, studies have shown that, in more chronic situations, microgravity may be the cause of cardiac arrhythmias and cardiac atrophy, which has been worrying scientists and physiologists. In this review, we will discuss the main changes observed in the cardiovascular system, in short and long duration flights, the way that they affect the homeostasis and the existing countermeasures that can mitigate these same effects.
Description
Trabalho Final do Curso de Mestrado Integrado em Medicina, Faculdade de Medicina, Universidade de Lisboa, 2020
Keywords
Microgravidade Fisiologia cardiovascular Voo espacial Controlo autonómico Intolerância ortostática Otorrinolaringologia