cdn.ymaws.com · Web viewYou can become confused and disoriented in an alien world where up and down have no meaning The brain gets confused and produces nausea and disorientation

1) Vestibular system Gravity provides a continual downward force, which the vestibular

system uses to process information about motion and orientation. Space motion sickness is caused by conflicting information that the brain

receives from the eyes and the vestibular organs in the inner ear. The eyes can see which way is up

and down inside the space shuttle; however the sensors in the vestibular system rely on the pull of gravity to tell up versus down.

The vestibular system is a fluid filled network of canals and chambers in the ear that help us keep our balance and know which way is up.

The vestibular-ocular reflex is the body’s way of coordinating signals from the visual field with signals from the vestibular organs of the inner ear. This reflex is extremely important for stabilizing vision when we are moving. When the head rotates or tilts in any direction, the eyes move in the opposite direction to compensate, maintaining a stable visual image. Therefore, movements of the eyes can provide clues about what is happening in the vestibular system. The eyes respond similarly to movement of objects outside the body. However, the vestibular-ocular reflex occurs only when the vestibular system is stimulated (in other words, when the head moves).

If you close your eyes in space how do you determine which way is up? The vestibular system doesn’t sense the familiar pull of gravity and the world can seem topsy-turvy.

You can become confused and disoriented in an alien world where up and down have no meaning

The brain gets confused and produces nausea and disorientation. Fortunately, after a few days the brain adapts by relying solely on the

visual inputs and astronauts begin to feel better; 60-70% of the astronauts experience nausea and loss of appetite.

What are the Space applications of studies aimed at understanding the behavior of the vestibular system in space?

And the Earth applications?

NASA uses the term “countermeasures” to describe the procedures, medications, devices, and other strategies that help keep astronauts healthy and productive during space travel and return to Earth. Can you envision any pre-, post- or during- mission countermeasure for this organ?

2) Proprioceptive system

Humans sense position and motion in three-dimensional space through the interaction of a variety of body proprioceptors, including muscles, tendons, joints, vision, touch, pressure, hearing, and the vestibular system. Feedback from these systems is interpreted by the brain as position and motion data. Our vestibular system enables us to determine body orientation, senses the direction and speed at which we are moving, and helps us maintain balance.

In microgravity there is no natural “up” and “down” determined by our senses

You don’t know the orientation of parts of your body, especially your arms and legs, because they have no weight for you to feel in space.

The proprioceptive system, the nerves in the joints and muscle that tell us where our arms and legs are without having to look, can be fooled by the absence of weight.

One Gemini astronaut woke up in the dark during a mission and saw a disembodied glow-in-the-dark watch floating in front of him; he realized moments later that the watch was around his own wrist

Many apes have their internal organs tethered at the top and bottom so when they swing from trees or hang upside down the organs stay in place; human organs are tethered mainly at the top so in microgravity they tend to shift around and that can cause nausea.

What are the Space applications of studies aimed at understanding the behavior of the proprioceptive system in space?



3) Fluid shift On Earth gravity

pulls on the blood causing it to pool in the legs.

In microgravity the blood shifts from the legs to the chest and head causing the legs to shrink in size, this is called “fluid shift”.

In microgravity the face will feel full, the sinuses congested, and you may get a headache (it feels the same way on Earth when you bend over or stand upside down, because the blood rushes to your head).

Upon returning to Earth, gravity will pull those fluids back down to the legs and away from the head causing fainting upon standing up; the astronaut will also begin to drink more and the fluid levels will return to normal in a few days.

The body senses an overabundance of fluids in the chest and head area and sends a message to the kidneys to eliminate the excess fluid by producing more urine.

Astronauts therefore do not feel thirsty and decrease their fluid intake;the result is up to a 22% loss of blood volume.

One way to deal with fluid loss in space is with a device called Lower Body Negative Pressure (LBNP). This device applies a vacuum-cleaner-like suction below your waist to keep fluids down in the legs.

In space astronauts spend 30 minutes a day in the LBNP to keep the circulatory system in near-Earth condition.

The LBNP helps with cardiovascular function by increasing blood pressure to the legs.

What are the Space applications of studies aimed at understanding the phenomenon of fluid shift in space?



4) Blood On Earth gravity pulls on the blood causing it to pool in the legs. In microgravity the blood shifts from the legs to the chest and head (fluid

shift) The body senses an overabundance of fluids in the chest and head area

and sends a message to the kidneys to eliminate the excess fluid by producing more urine.

Moreover, astronauts do not feel thirsty and decrease their fluid intake; the result is up to a 22% loss of blood volume.

As the kidneys eliminate excess fluid, they also decrease their secretion of erythropoietin, a hormone that stimulates red blood cell production by bone marrow cells.

However, astronauts experience significant symptomatic anemia caused by neocytolysis, a process that selectively ruptures new red blood cells. This happens under certain conditions on Earth as well, such as moving from high altitude to sea level.

Anemia, the decrease of red blood cells in the blood, is observed within 4 days of spaceflight and decrease by ~15% after a 3-month stay.

Upon returning to Earth the erythropoietin level and red blood cell count will return to normal.

What are the Space applications of studies aimed at understanding the response of blood in space?



5) Heart An astronaut’s circulatory

system, which is accustomed to working against gravity, receives a different set of signals and stimuli in microgravity and adapts to the new environment.

The heart does not need to work as hard to send blood to the upper body as it does when it working against gravity. This causes blood volume to increase in the upper body.

The change in blood volume affects the heart, too. If you have less blood volume then the heart doesn’t need to pump as

hard. Because it no longer has to work as hard, the heart will shrink in size. The human heart is designed to force blood to the body, and the most

difficult organ to perfuse is the brain since it is above the heart. Since the heart is less efficient some blood remains in the heart after

each contraction which slightly increases the pressure during the relaxation phase known as diastole. Taken together, the amount of blood that is being pumped out of the heart (stroke volume) will change.

In space the heart does not have to work against gravity to pump blood to your brain and blood accumulates in the upper body because gravity is not there to pull it toward the feet. The body takes advantage of this lack of work and begins to be less efficient as demonstrated by the lower stroke volume. The heart generates slightly higher systolic and diastolic pressures.

Because large muscle groups (like the legs) are inactive and do not demand blood, this results in vasoconstriction.

As the flight duration increases, these changes become slightly more dramatic, and may affect an astronaut’s other physiological functions. There could even be permanent changes in the way organs and blood vessels behave.

What are the Space applications of studies aimed at understanding how heart responds in space?



6) Muscles Muscles are adaptable tissues;

in microgravity muscles atrophy quickly because the body perceives it does not need them.

The muscles used to fight gravity and maintain posture can vanish at the rate of 5% a week.

Reducing the load by lying in bed or living in microgravity will make them grow smaller and weaker.

After only 11 days in space microgravity can shrink muscle fibers as much as 30%.

Loss of muscle mass makes you weaker, presenting problems for long-duration space flights and upon returning home to Earth’s gravity.

Fortunately muscles recover rapidly after weeks in microgravity. But what might happen during years-long missions, like a trip to Mars? Could more vigorous aerobic workouts prevent muscle wasting or are

other exercises more effective? International Space Station research will help develop workouts to

minimize or prevent muscle atrophy. The best way to minimize loss of

muscle and bone in space is to exercise frequently, mainly with the treadmill, rowing machine, and bicycle.

This prevents muscles from deteriorating and places stress on bones to produce a sensation similar to weight.

What are the Space applications of studies aimed at understanding how muscles responds in space?



7) Bones On Earth the bones support the weight

of the body. The size and mass of the bones are

balanced by the rates at which osteoblasts lay down new mineral layers and osteoclasts chew up those mineral layers.

In microgravity the bones do not need to support the body.

All of the bones, especially the weight-bearing bones in hips, thighs and lower back, are used much less than they are on Earth.

The size and mass of these bones continue to decrease as long as astronauts remain in microgravity at a rate of about 1-2% a month.

The bones most commonly effected are the lumbar vertebrae and the leg bones.

Space travelers can lose on the average of 1-2% of bone mass each month.

It is not known how much of this bone loss is recoverable after returning to Earth, although it is probably not 100%.

Weakening of the bones due to a progressive loss of bone mass is a limiting factor for space flight duration.

What are the Space applications of studies aimed at understanding how bones responds in space?



8) Kidney On Earth the bones support

the weight of the body, but in microgravity the bones do not need to support the body

The size and mass of the bones are balanced by the rates at which osteoblasts lay down new mineral layers and osteoclasts chew up those mineral layers.

Bone demineralization increases the risk of developing renal stones. Renal stones, popularly known as kidney stones, are small rock-like

objects made from deposits of calcium and other minerals that form in the kidneys or urinary tract.

Normally, calcium and protein, along with other minerals that build bone and muscle, are transferred to the bloodstream and then to the kidneys, where they are flushed out with bodily fluid. Without sufficient amounts of fluid, crystals can form and grow into stones.

When stones block kidney drainage, they result in urinary obstruction and pain.

Renal stones can be extremely debilitating and, when they occur during spaceflight, can potentially end a mission.

Medical therapy options that are widely available on Earth are severely limited during long-duration space exploration. Therefore, preventing renal stone formation is the most logical and cost-effective approach for spaceflight missions.

Renal stones can usually be prevented by modifying fluid intake, adjusting the diet, and taking medication.

What are the Space applications of studies aimed at understanding how kydney responds in space?



9) Circadian cycle Space travelers sleep

an average of 2 hours less a night than they do on Earth.

Human intrinsic circadian rhythm is 24.1 + 0.15 h.

In low Earth orbit the Sun rises and sets every 90 minutes which adds to astronouts’ sleeplessness.

This can disrupt the circadian rhythms that ensure a good night’s sleep. Maintaining synchronized circadian rhythms is important to health and

well-being. Fatigue in space, as on Earth, is a serious problem; it can affect

performance, increase irritability, diminish concentration, and decrease

reaction time.

What are the Space applications of studies aimed at understanding how the circadian cycle changes in space?



10) Immune system

The human immune system is a complicated network of different cell types (granulocytes, lymphocytes, monocytes, etc.), that reside in various tissues throughout the body.

Immune cells primarily reside in the blood and lymph nodes, and migrate to any tissue where disease or injury may occur.

Research suggests that immune system suppression occurs during spaceflight; however, the magnitude and specific nature of the suppression are unknown. Should the immune system remain compromised for the duration of an exploration-class space mission (such as to the Moon or Mars), this would result in greater crew risk for contracting illnesses.

Humans have many viruses in their bodies that are kept at bay by our immune system.

Space flight is very stressful and latent viruses are very often activated. This can make astronauts susceptible to viral infections.

Risks associated with most bacterial, fungal, viral and parasitic pathogens can be reduced by a suitable quarantine period before the flight and by appropriate medical care. However, latent viruses (viruses that lie dormant in cells, such as herpes viruses that cause cold sores) already inside the cells of crewmembers are unaffected by such actions and pose an important infectious disease risk to crewmembers involved in space flight and space habitation.

What are the Space applications of studies aimed at understanding how the immune system responds in space?

Herpes Simplex virus

Epstein-Barr virus



11) Skin A study on 19 crew members of 6 NASA-Mir missions, from 1995 to

1998, indicated that small cutaneous injuries were the most frequent medical incidents.

Recorded complaints include skin dryness and itching making it more susceptible to scratches and irritation.

Several cutaneous physiological changes were recorded after the mission such as coarsening of the epidermis and decreased skin elasticity.

The most significant change was a thinning of the dermal matrix similarly to the skin atrophy observed in aging on Earth.

A prolonged exposure to space conditions may induce skin atrophy and deregulate hair follicle cycle.

Long-duration missions in microgravity affect skin by causing excessive dryness, increased cell loss and increased aging.

What are the Space applications of studies aimed at understanding how skin responds in space?



12) Eyes Approximately 20% of

astronauts living on the International Space Station have reported post-flight vision changes.

Previous research identified a possible link between the reported vision changes and increased intracranial pressure caused by shifts in bodily fluids from the lower extremities to the upper part if the body, due to microgravity. This may still be part of the problem, but the new study shows there may be other contributing factors.

Many astronauts experience poorer vision after flight, some even for years after.

A number of studies have looked for causes and distinct physical changes in the eye itself have been found.

MRI scans suggest that pressure changes in the brain and spinal fluid caused by weightlessness may be partly to blame.

A nutrition study included 20 astronauts, with 5 experiencing vision or eye anatomy changes. Comparing the blood analysis with nutritional assessments revealed that crew members experiencing vision changes had consistently lower folate levels and higher levels of metabolites.

Many astronauts do not show these effects, though, and more advanced imaging techniques may be needed to understand the role of changing brain pressure in microgravity.

What are the Space applications of studies aimed at understanding how eyes responds in space?



13) Respiration Inside space shuttles there are sensors to monitor and regulate the

cabin atmosphere which includes gas concentrations and pressures within the space shuttle cabin.

Maintaining these parameters ensures a habitable cabin atmosphere and temperature on board the space shuttle much like the atmosphere here on Earth.

These conditions allow the crew to work in a “shirt sleeve” environment while in the cabin (i.e. the crew can wear normal clothing rather than the protective clothing that is necessary outside of the cabin area).

Air is circulated in the space shuttle cabin using fans that force the air through cabin air loops where the air is conditioned.

Conditioning the air involves a series of processes that remove dust particles, heat, humidity, and carbon dioxide (CO2).

The absorption method used to remove carbon dioxide from the air involves a chemical reaction using lithium hydroxide (LiOH) as the sorbent. Lithium hydroxide is an attractive choice for space flight because of its high absorption capacity for carbon dioxide and the small amount of heat produced in the reaction.

Lithium hydroxide canisters are located in mid deck of the space shuttle and their replacement is a daily activity during space shuttle flights.

There is a potential for some toxicity within the space shuttle cabin due to lithium hydroxide dust that could be ingested by the crew.

Suppose in an emergency situation there is an

unexpected drop in O2 partial pressure: Crewmembers begin to exhibit symptoms similar to those of high altitude mountain climbers that could be from one or a combination of gas factors.

The following are symptoms that may result:o Muscular System – lactic acid build up and fatigue as oxygen to

cells decreases and anaerobic respiration increases.o Circulatory System – vasodilation when low O2 in arteries leads

to efforts to increase O2 delivery rate.o Respiratory System – vasoconstriction and shortness of breath

occur due to lack of proper oxygenation.o Nervous System – varies with person, feelings of euphoria,

headache, fatigue, confusion, decrease in motor control, cognitive disturbances with tasks and memory, fainting, cessation of brain stem reflexes, death.

What are the Space applications of studies aimed at understanding how respiration works in space?


NASA uses the term “countermeasures” to describe the procedures, medications, devices, and other strategies that help keep astronauts healthy and productive during space travel and return to Earth. Can you

envision any pre-, post- or during- mission countermeasure for this organ?

Exercise and diet

NASA is studying and improving food formulation, processing, packaging, and preservation systems to ensure the nutrients remain stable and the food remains acceptable. Space-resilient medications and packaging that preserve the integrity of pharmaceuticals for long duration missions have also been developed.

LED sleep, insomnia shift workers elderly sleep medications, Journals to descerase depression

applications in understanding reaction times, lapses of attention, sleepiness, and

impulsivity caused by fatigue and other factors found in demanding operational

environments

rehabilitation programs

fluid shift

benefit people confined to long-term bed rest

compression cuffs on the tights

The risk of fainting and falling is increased in older adults.

Balance and coordination

the ability to perform such tasks, and how quickly that ability is recovered, is expected to

provide important information for planning of future exploratory missions

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cdn.ymaws.com · Web viewYou can become confused and disoriented in an alien world where up and down have no meaning The brain gets confused and produces nausea and disorientation