Changes in Physiology Due to Spaceflight

**13**

**Chapter 2**

**Abstract**

ity exposure.

**1. Introduction**

these body systems.

Physiology

*and Tadaaki Mano*

Effects of Microgravity on Human

The effects of microgravity conditions on neurovestibular, cardiovascular, musculoskeletal, bone metabolic, and hemato-immunological systems are described. We discuss "space motion sickness," sensorimotor coordination disorders, cardiovascular deconditioning, muscular atrophy, bone loss, and anemia/ immunodeficiency, including their causes and mechanisms. In addition to the previously described deconditioning, new problems related to microgravity, spaceflight-associated neuro-ocular syndrome (SANS), and structural changes of the brain by magnetic resonance imaging (MRI) are also explained. Our proposed countermeasure, artificial gravity produced by a short-arm centrifuge with ergometric exercise, is also described in detail, and we confirmed this system to be effective in preventing the abovementioned deconditioning caused by micrograv-

**Keywords:** microgravity, neurovestibular, neural plasticity, cardiovascular,

Outer space offers several abnormal and/or unique environmental conditions, including microgravity, vacuum/hypovaria, acceleration, extreme temperature, space debris, space radiation, and confinement/isolation. As the latter four conditions may be mitigated by spacecraft engineering (i.e., pressurization and the bulkhead), we

In spaceflight, astronauts face three periods of physiological adaptation induced by changing gravity: (1) changes upon entry to microgravity (initial adaptation), (2) changes after prolonged exposure to microgravity, and (3) readaptation to 1 G gravity on Earth after returning from space. Body systems influenced by microgravity are the neurovestibular, cardiovascular, musculoskeletal, bone metabolic, and immuno-hematological systems. The changes associated with these systems occur during the adaptation phases outlined above. We will briefly discuss each of

musculoskeletal, bone metabolism, hematology and immunology

focused on microgravity and its effects on human physiology [1–8].

*Satoshi Iwase, Naoki Nishimura, Kunihiko Tanaka* 
