Assessment of Programs in Space Biology and Medicine--1991 (1991) / Chapter Skim
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3. HUMAN PHYSIOLOGY
3. HUMAN PHYSIOLOGY
Pages 20-33
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From page 20... ...
First and of greatest concern is bone, muscle, and mineral metabolism; second, cardiovascular and homeostatic functions; and third; sensorimotor integration. BONE, MUSCLE, AND MINERAL METABOLISM Status of the Discipline The bone and muscle atrophy that occurs in the microgravity environment is a severe hurdle to an extended human presence in space.
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From page 21... ...
or muscle atrophy is understood. While countermeasures to inhibit or prevent this bone loss are imperative, this goal will only be realized following an improved understanding of the basic cellular mechanisms responsible for the maintenance of muscle and bone mass.
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From page 22... ...
to factors such as diminished bone mass and increased urinary calcium have proven useful models to understanding the risks of skeletal fracture or mineral disorders during extended spaceflight. Lack of Progress While significant work has been done, and NASA investigators have established collaborations with superb musculoskeletal and connective tissue scientists at a number of university centers, it must also be emphasized that the directions for future programs are not yet clear.
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From page 23... ...
within the musculoskeletal system should also be considered. Before reasonable prophylaxes for bone loss can be developed, the basic cell and subcellular mechanisms responsible for this osteopenia must be understood.
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mechanisms responsible for postflight orthostatic intolerance; (3) the long-term, possibly irreversible, effects of the altered loading conditions in microgravity, e.g., atrophy of heart muscle, chronic orthostatic hypotension; and (4)
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From page 25... ...
flight will be discussed as a means of enhancing elementary and secondary school science classes. With joint participation by NASA, ESA, and the German Space Program, the D-2 flight will extend the range of measurements and interventions with detailed observations during intravenous fluid load and lower body negative pressure.
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From page 26... ...
For example, it is not possible to accurately determine the overall pattern of adrenal cortisol secretion (a stress-related hormone) by simply taking a single blood sample on a daily basis.
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Immunology, Hematopoiesis, and Wound Healing Status of Discipline Immune cells in mammalian bone marrow and lymphoid organs, such as the thymus and spleen, provide integrated and adaptive host defense against infections, other external environmental challenges, and deviations in host cellular growth and differentiation. Many of the cells and proteins of the immune system, which initiate and regulate lymphocyte and antibody responses, also control the production and functions of cells in the blood and connective tissues.
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From page 28... ...
Studies of the mechanisms for reduction in red blood cell mass with spaceflight and of effective countermeasures for attenuated compensation to bleeding and blood clot formation are recommended. Gastrointestinal System and Nutrition Major Goals A Strategy for Space Biology and Medical Science for the 1980s and 1990s recommends studies of caloric needs, nitrogen balance, supplements to the basic diet during spaceflight, and the energetic requirements of work in space.
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From page 29... ...
Because the otolith organs of the vestibular labyrinth are the primary sensors informing the brain of the linear accelerations induced by gravity, the research recommended focuses on neural mechanisms that transform vestibular sensory inputs (especially those from otolith organs) into sensations, movements, and changes in homeostatic state (i.e., space adaptation sickness)
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From page 30... ...
The Goldberg Strategy concludes that neural processing mechanisms in the vestibular system must be investigated both in normal gravity and microgravity if NASA is to achieve its goal of controlling for sensorimotor changes and space adaptation sickness. These studies would focus on the vestibular nuclei of the brainstem, which serve both as the point at which vestibular signals from receptors of the vestibular labyrinth in the inner ear enter the brain and as a primary processing center for all signals -- vestibular, visual, and proprioceptive (sense of body position)
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From page 31... ...
These have generated useful information in the areas of spatial sensation, vestibular processing, posture and gaze control, and vestibular-autonomic interactions. A promising development is the establishment of the Vestibular Research Facility (VRF)
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From page 32... ...
The issue of whether observed instances of sensorimotor difficulties are, or are not, entirely a function of disturbed vestibular processing has become of operational importance in connection with ongoing and projected increases in mission duration (letter to Administrator Truly, NASA, regarding extended duration orbiter medical program, December 20, 1989)
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From page 33... ...
Similarly, issues related to neural processing are being dealt with properly, although a great deal of work remains to be done. It remains the case that no single hypothesis as to the origin of space motion sickness fits all existing observations, and no single therapeutic regime with assured effectiveness has yet been developed.
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