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Physiology in Space

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WHAT’S DIFFERENT ABOUT SPACE?

Gravity Fields

Hostile Environment

Isolation

Space Radiation

Distance from Earth

A person on earth experiences a very different environment than a person living in space. Most people think about gravity being the only difference. While gravity is an important factor that changes how the body functions in spaceflight, it’s not the only one! A person exposed to spaceflight experiences isolation and confinement, a potentially hostile and closed microbial environment, exposure to space radiation, and the potential psychological effects of being distanced from earth too. Each of these factors can cause changes in the way that the body responds in the unique environment of space. Together, we call these factors “spaceflight stressors”. NASA has to consider each one of these spaceflight stressors when they propose solutions for protecting human health in space.

Source: https://www.nasa.gov/sites/default/files/atoms/files/your_body_six_month_in_space_11_18_15_0.pdf

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THE BODY IN SPACE

Vision Changes

Bone Density Loss

Gene Expression Changes

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QUICK DISCUSSION:

Have you ever been on a rollercoaster?

Turn to the people sitting near you and talk about what you felt during the ride.

Think about how it felt when the coaster went over the first big hill.

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BIO-FLUID MECHANICS

Fluid Shift: a change in the way that fluids in the body are distributed throughout the body due experienced by astronauts in free fall on the space station.

For those who have been on a rollercoaster, did you experience the feeling of floating as you went over the first hill? You might have felt like all the blood in your body rushed to your head. Astronauts on the space station are experiencing a somewhat similar phenomenon. As the international space station orbits the earth, the astronauts are in a free fall that places them in a microgravity environment. When this happens, they experience a fluid shift that changes where fluid is distributed throughout the body. On earth, most of the fluid in your body rests in your lower extremities (ie. Your legs). However, in space, fluid evenly distributes through the body, meaning you have more fluid near your heart and surrounding your brain than you may be used to. That fluid shift is thought to play a major role in many of the physiological changes that an astronaut experiences.

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WHAT HAPPENS TO THE BODY IN SPACE?

Eyes: Many astronauts suffer from vision loss. It might be due to fluid pressure or to cosmic rays
Brain: The brain can be disoriented as it continually searches for gravity.
Heart: In space, hearts don’t have to work as hard to pump blood. This can mean that the muscle gets smaller
Bones and muscles: These deteriorate in space from a lack of use
Spine: Astronauts get taller in space, since gravity isn’t compressing the backs

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GENETIC CHANGES

Gene expression: the turning on or off of genes, resulting in a change in how the body functions.

Gene: the biological material in the body that determines traits and how the body functions.

Your body is made up of a special collection of biological material that determines what you look like and how your body functions, called genes. You can think of genes, which we inherit from our parents, like an instruction booklet that tells your body how to work. Genes can be turned on and off (think like a stoplight that can turn red or green to direct traffic to follow a certain pathway), and the environment around us can influence how that expression occurs. A lot of research has shown that being stressed can change how genes function, so NASA is curious to see how spaceflight stressors change the way that our genes are expressed. They studied this using a courageous set of twins, known as the Kelly brothers. Mark and Scott Kelly are both astronauts for NASA. Mark stayed on Earth for a year while his twin brother Scott went to live on the international space station for an entire year. Twins are very valuable for scientists to look at how the environment changes gene expression, since they are born with the same genetic makeup but their environment can change which genes are turned on or off. After a year, NASA found that Scott’s exposure to spaceflight stressors caused his genes to behave differently than his earth-bound twin Mark. This is important for us to research more as we send people into space for longer amounts of time.

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BONE CHANGES

Osteoporosis: the loss of bone density.

Bone density can decrease by as much as 1-2% each month in a microgravity environment.

One of the big problems that NASA sees in astronauts that travel to space is a loss of bone density. When you lose your bone density, your bones become weak and are more likely to break. Losing bone density is known as osteoporosis, and its something that happens here on Earth too. NASA has found that spaceflight stressors cause astronauts to lose bone density MUCH faster than people normally do on earth- even as fast as 1-2% of their bone density each month! This means that if an astronaut is in space for a long time, they are in increasing danger of breaking their bones. NASA researchers have found that exercise is an important way to prevent that bone loss from happening. Astronauts on orbit are required to spend and average of 2 hours each day completing exercises that help prevent bone loss. Whether you’re on earth or in space, exercise is very important!