Comparative analysis of the stretch reflexes characteristics in human under condition of real and simulated microgravity
- Paper number
IAC-08.A1.2.11
- Author
Dr. Irina Sayenko, Institute for Biomedical Problems, Russia
- Coauthor
Prof. Inessa Kozlovskaya, Institute of Biomedical Problems (IBMP), Russia
- Year
2008
- Abstract
The analysis of the time course of tendon reflex parameters alteration under conditions of real and simulated microgravity has been provided to understand the mechanisms of the microgravity effects. The studies were performed in short-term Space Flights, long-term Space Flights (SF), 120-days - 6o head-down tilt Bed Rest (BR). Electromyographic and kinematic parameters of the knee reflex were studied by means of the specially developed neurological equipment - MONIMIR, which consisted of the lodgement, that ensured standard position of the tested extremity in supine position of the subject, and mechanical device that produced spring strokes of standard intensities on the patellar tendon. The system for amplifying and recording ("Datamir") provided registration of electromyographic responses Exposures to both real and simulated microgravity was followed consistently by an intensive hyperreactivity of the stretch reflexes, that showed up by a significant decrease of the thresholds of responses and the appearance of clonus. Alterations of the reflex amplitude under different microgravity conditions weren't unidirectional. In BR the alteration curve of T-reflex displayed from the first day of the exposure a significant increase of the amplitude. In the real weightlessness the curve of changes revealed consistently two phase: In the first one developed in the first days of exposures and lasted up to a month the amplitude of the reflex EMG amplitude was lowered, though the intensive clonic activity pointed out to a great hyperreactivity of the reflex mechanisms. In the second phase, started after 30th day of SF, it increased greatly reaching values of 8-9 mV and higher to the 60th day of flight and later. The changes of the reflex amplitudes during long-term exposures to microgravity, ambiguous in different models of microgravity and at different phases of exposures, are caused by different factors, namely: by the acute and chronic deafferentation - the decline and subsequent increase of the amplitude in long-term space flights and in the first phase of BR; and by the muscle atrophia in the later phase of BR.- Abstract document
- Manuscript document
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