EFFECTS OF MICROGRAVITY

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EFFECTS OF MICROGRAVITY
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ACCELERATION

• FIRST PROBLEM ASTRONAUTS FACE
• SPEED IS NOT A PROBLEM
• YOU ARE CURRENTLY TRAVELING AT APPROXIMATELY
  67,000 MPH THROUGH SPACE AS THE EARTH ORBITS THE
  SUN AND SPINNING AT APPROXIMATELY 1,000 MPH AS
  THE EARTH TURNS ON ITS AXIS

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• ACCELERATION IS MEASURED IN TERMS OF G-FORCE
  WHERE 1 G IS THE PULL OF THE GRAVITY ON THE
  SURFACE OF THE EARTH
• GRAVITY 9.806 N/KG
• 1 NEWTON FORCE REQUIRED TO GIVE A MASS OF 1
  KG AN ACCELERATION OF 1 M/SEC/SEC (1 METER PER
  SECOND SQUARED)

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• GREATEST G FORCE OCCURS AS
• THE SPACECRAFT ACCELERATES AS IT ENTERS ORBIT
  WHEN IT IS MUCH LIGHTER (MOST OF THE FUEL HAS
  BEEN USED) AND THE ROCKETS ARE STILL AT FULL
  THRUST
• THE SPACECRAFT DECELERATES DURING RE-ENTRY INTO
  THE EARTHS ATMOSPHERE

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EFFECTS OF INCREASED G FORCE

• 2 G - BODY FEELS HEAVIER, FACIAL TISSUES SAG,
  AND IT IS DIFFICULT TO STAND-UP FROM SITTING
  POSITION
• 3G - IMPOSSIBLE TO STAND AND COLOR VISION FADES
  AS A GRAY CURTAIN SETS IN AS G-FORCE FURTHER
  INCREASES
• 4.5 G - VISION IS LOST
• 8 G - IMPOSSIBLE TO RAISE ARMS OR LIFT HEAD
• 12 G - CONSCIOUSNESS LOST

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EFFECTS OF INCREASED G FORCE

• G FORCE PULLS BLOOD INTO LOWER EXTREMITIES,
  HEART CAN NOT COMPENSATE, AND UNCONSCIOUSNESS
  OCCURS
• GAS EXCHANGE ALSO DECREASES AS DIAPHRAGM IS
  PULLED DOWNWARD RESULTING IN BREATHING DIFFICULTY
  AND DECREASED ALVEOLAR VENTILATION

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• NOTE AN ADDITIONAL PROBLEM AT TAKE-OFF IN
  ADDITION TO THE INCREASED G FORCE IS THE SEVERE
  VIBRATIONS RESULTING IN IMPAIRED ABILITY TO
  PERFORM MANUAL TASKS, NAUSEA, HYPERVENTILATION,
  AND PHYSICAL COLLAPSE

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EFFECTS OF WEIGHTLESSNESS
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EFFECTS OF WEIGHTLESSNESS

• ASTRONAUTS GROW TALLER
• DECREASED RED BLOOD CELL PRODUCTION AS (1) THE
  SHIFT OF BLOOD TO THE CHEST TRICKS THE BODY INTO
  THINKING THAT IT HAS TOO MUCH BLOOD VOLUME, WHICH
  LEADS TO A DECREASE IN ERYTHROPOIETIN RELEASED
  FROM THE KIDNEYS AND HENCE RBC SYNTHESIS BY THE
  BONE MARROW AND (2) RBCs WAITING TO BE RELEASED
  FROM THE BONE MARROW ARE DESTROYED

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EFFECTS OF WEIGHTLESSNESS

• DECREASED BLOOD VOLUME
• NOTE THE INCRESED BLOOD VOLUME IN THE THORACIC
  CAVITY DUE TO FLUID SHIFTS INCREASES BLOOD
  PRESSURE, WHICH LEADS TO DECREASED ANTI-DIURETIC
  HORMONE (ADH) AND ALDOSTERONE RELEASE AS WELL AS
  DECREASED SNS ACTIVITY RESULTING IN INCREASED
  URINE PRODUCTION AND DECREASED BLOOD VOLUME

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EFFECTS OF WEIGHTLESSNESS

• DECREASED OXYGEN CARRYING CAPACITY OF THE BLOOD
• INCREASED BLOOD VISCOSITY WHICH INCREASES
  RESISTANCE TO BLOOD FLOW
• INCREASED RESISTANCE TO BLOOD FLOW POTENTIALLY
  DECREASES CARDIAC OUTPUT
• AND/OR INCREASES BLOOD PRESSURE
• DECREASED PHYSICAL WORK CAPACITY

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EFFECTS OF WEIGHTLESSNESS

• LOSS OF LEAN BODY WEIGHT (BONE, MUSLCE, AND
  CONNECTIVE TISSUE) AND CARDIAC TISSUE WHICH ALSO
  CONTRIBUTES TO A DECREASE IN PHYSICAL WORK
  CAPCITY
• BONE LOSS DUE TO REDUCED BONE STRESS
• MUSCLE LOSS DUE TO REDUCED USE
• CARDIAC ATROPHY DUE TO DECREASED BLOOD VOLUME
  AND DECREASED GRAVITATIONAL PULL
• ASTRONAUTS EXERCISE SEVERAL HOURS PER DAY IN
  ORDER TO MINIMIZE LOSS OF LEAN BODY WEIGHT AND
  CARDIAC TISSUE

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EFFECTS OF WEIGHTLESSNESS

• SLEEP DIFFICULTY DUE TO LITTLE SENSE OF
  PRESSURE AND HENCE SECURITY
• ASTRONAUTS SLEEP IN SLEEPING BAGS ATTACHED
  TO WALLS WITH HEAD AND KNEE STRAPS TO INCREASE
  SENSE OF PRESSURE
• NEED TO SLEEP IN VENTILATED AIR FLOW TO
  INSURE THAT EXHALED CO2 IS NOT RE-INHALED

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EFFECTS OF WEIGHTLESSNESS

• INCREASED SPREAD OF INFECTIOUS DISEASES AS
  BACTERIA FROM SKIN AND SNEEZES/COUGHS FLOATS IN
  CIRCULATING AIR FOR LONGER PERIODS OF TIME
  WITHOUT GRAVITY
• SPACE SICKNESS (HEADACHES, NAUSEA, DIZZINESS,
  LOSS OF APPETITIE, LACK OF MOTIVATION, DROWINESS,
  AND IRRITABILITY) DUE TO TILTING THE HEAD FORWARD
  OR BACKWARD OR A VISUALLY DISORIENTATING SCENE

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COSMIC RADIATION

• ON EARTH THE ATOMOSHERE AND EARTHS MAGNETIC
  FIELD SHIELDS MOST RADIATION EXCEPT FROM VISABLE
  LIGHT AND RADIO WAVES
• THREE SOURCES OF EXTRETERRESTRIAL RADIATION
  THAT ASTRONAUTS EXPERIENCE ARE GALATIC RAYS,
  SOLAR RADIATION, TRAPPED BELT RADIATION (E.G.,
  VAN ALLEN BELT THAT ENCIRCLES EARTH LIKE A HOLLOW
  DONUT)

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COSMIC RADIATION

• RADIATION LEVELS ARE USUALLY LOW
• LONG TERM EXPOSURE MAY
• DAMAGE GENETIC MATERIAL (DNA) THEREBY
  INCREASING THE RISK OF CANCER
• DAMAGED GERM CELLS (SPERM AND EGG CELLS)
  MAY CAUSE INFERTILITY OR GENETIC ABNORMALITIES
  IN THE CHILDREN OF ASTRONAUTS

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COSMIC RADIATION

• ASTRONAUTS CARRY RADIATION DOSIMETERS
• RADIATION EXPOSURE IS USUALLY WITHIN ACCEPTABLE
  LIMITS ALTHOUGH ASTRONAUTS WHO SPEND A LONG TIME
  IN SPACE CRAFTS OR WORK STATIONS MAY HAVE
  RECEIVED A SIGNIFICANT DOSE
• SUPERSONIC AIRCRAFTS (E.G., CONCORDE) CRUISE
  CLOSE TO THE EDGE OF THE EARTHS ATMOSPHERE AND
  ARE NOT SHIELDED FROM COSMIC RADIATION, ALTHOUGH
  IT WOULD TAKE 14 ROUND TRIP FLIGHTS FROM LONDON
  TO NEW YORK TO REACH TOXIC LEVELS

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SOLAR FLARES
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SOLAR FLARES
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SOLAR FLARES

• VERY HIGH INTENSITY RADIATION
• KILLS CELLS OUTRIGHT
• DEATH MAY OCCUR WITHIN HOURS DUE TO DAMAGE TO
  THE CENTRAL NERVOUS SYSTEM OR WITHIN A FEW DAYS
  DUE TO DESTRUCTION OF WHITE BLOOD CELLS OR THE
  RAPIDLY-DIVIDING CELLS THAT LINE THE INTESTINAL
  WALLS

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RETURNING TO EARTH

• UNABLE TO STAND WITHOUT FAINTING (I.E., FAILURE
  OF THE ORTHOSTATIC TOLERANCE TEST) DUE TO
• FLUID SHIFTS BACK TO LOWER EXTREMITIES DUE
  TO GRAVITY
• BLOOD VOLUME IS DECREASED
• MUSCLE PUMPING IS IMPAIRED DUE TO LOSS OF
  MUSCLE MASS
• THEREFORE, POOLING OF BLOOD OCCURS IN THE LOWER
  EXTREMITIES WHICH DECRESES END-DIASTOLIC VOLUME,
  STROKE VOLUME, AND CARDIAC OUTPUT

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RETURNING TO EARTH

• LOSS OF MUSCLE MASS MAKES IT DIFFICULT TO WALK
• DIFFICULT TO MAINTAIN BALANCE OR REMAIN UPRIGHT
  WITH EYES CLOSED
• DIZZINESS AND NAUSEA
• INCREASED RISK OF INJURY

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RETURNING TO EARTH

• MOVEMENT OF HEAD RESULTS IN FALSE ILLUSIONS
  THAT THE WORLD, RATHER THAN THE HEAD, IS MOVING,
  SUGGESTING THAT SIGNALS FROM RECEPTORS IN THE
  SEMICIRCULAR CANALS OF THE EARS (WHICH RESPOND TO
  LINEAR ACCLERATION) NEED TO BE RE-PROGRAMMED BACK
  FROM A MICROGRAVITY ENVIRONENT TO A GRAVITATIONAL
  ENVIRONMENT

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QUESTIONS??
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CARDIOVASCULAR SYSTEM IN SPACE

• HOW DOES WEIGHTLESSNESS IN SPACE AFFECT
• BODY FLUID DISTRIBUTION?
• BLOOD VOLUME?
• RED BLOOD CELL LEVEL?
• MUSCLE AND BONE MASS?
• IMMUNE SYSTEM?
• FACIAL EDEMA?
• LEG SHAPE?

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CARDIOVASCULAR SYSTEM IN SPACE

• HOW DOES WEIGHTLESSNESS IN SPACE AFFECT
• MOTION SICKNESS?
• EXERCISE CAPACITY?
• HEADACHES?
• POST-FLIGHT ORTHOSTATIC TOLERANCE?
• KNOW AND UNDERSTAND IN GENERAL HOW RESEARCH FOR
  WEIGHTLESSNESS IN SPACE MAY HELP SOLVE MEDICAL
  AND HEALTH PROBLEMS ON EARTH.

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MUSCULOSKELETAL SYSTEM IN SPACE

• HOW DOES WEIGHTLESSNESS IN SPACE AFFECT
• WEIGHT-BEARING WEAKNESSES IN MUSCLE,
  CARTILAGE, AND BONE?
• HEAVY WORK IN SPACE?
• MUSCLE ATROPHY?
• MUSCLE TONE AND STRENGTH?
• MUSCLE FATIGUE?
• MUSCLE SYNERGISM?
• MOTOR CONTROL?

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MUSCULOSKELETAL SYSTEM IN SPACE

• HOW DOES WEIGHTLESSNESS IN SPACE AFFECT
• MOTOR-END PLATE DEGENERATION?
• CONTRACTION VELOCITY?
• BONE MINERALIZATION?
• CONNECTIVE TISSUE?
• BACK PAIN?
• KNOW AND UNDERSTAND IN GENERAL HOW RESEARCH FOR
  WEIGHTLESSNESS IN SPACE MAY HELP SOLVE MEDICAL
  AND HEALTH PROBLEMS ON EARTH.