Download Bone Loss in Space Enrichment LESSON 1

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Bone Loss in Space
NASA has long known that space travel
takes a toll on the human body. For
example, the small force of gravity in space
negatively affects the circulatory system.
On Earth, gravity helps blood flow from
the upper body to the lower body. So the
heart pumps blood more forcefully to the
upper body and relies on gravity to balance
the flow to the lower body. In space,
however, this balancing force of gravity is
absent. The heart continues to pump blood
more forcefully to the upper body, but
blood flow to the lower body is uneven. As
a result, astronauts in space tend to develop
puffy faces and thin lower bodies.
Bone Loss
Other Health Problems
Bone loss and decreased circulation are
not the only health problems facing
astronauts in space. The shape of the spine
also changes. Without gravity to force the
vertebrae together, the spine stretches out—
sometimes painfully.
In addition, the body’s balancing system
is affected by space travel. On Earth, the
brain analyzes information from the eyes,
muscles, tendons, and sensors in the inner
ear. In space, this information is gathered
by the eyes alone. Astronauts have a
difficult time moving around in space.
Limits to Space Exploration
NASA has sent crewless spacecraft to the
far reaches of the solar system and beyond.
On these long missions, NASA relies on
robots and other technology to gather data.
These technologies are limited in that they
cannot react to and assess new situations as
quickly as humans can. But until health
issues in space are addressed, NASA cannot
send astronauts on long-term missions.
According to a program scientist for the
International Space Station, “The success of
human exploration missions depends on
finding countermeasures to overcome
[negative health] effects on crew members.”
Applying Critical-Thinking Skills
Directions: Answer each question or respond to each statement.
1. Summarize the causes and effects of health problems in space.
2. Assess Do you think the study of health problems in space is a priority for NASA? Use
facts from the article to support your answer.
Structure and Movement
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
The most serious health problem for
astronauts is bone loss. In space, bones
lose important minerals such as calcium,
potassium, and sodium. According to a
recent NASA study, astronauts aboard the
International Space Station lost an average
of 11 percent of the bone mass in their
hips. Their rates of bone loss were nearly
12 times as high as those of an elderly
woman on Earth.
Within a year, much of the astronauts’
bone mass had returned. However, they
still had not regained full hip strength, and
bone density had only slightly increased.
The astronauts aboard the space station
exercise about two hours each day to
counter the problem. Exercise appears to
slow bone loss, but it does not solve the
problem completely.