WEBVTT

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- WE ALL KNOW
THAT NASA ASTRONAUTS

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GO THROUGH A LOT OF TRAINING,

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BOTH PHYSICAL AND MENTAL,
BEFORE GOING INTO SPACE.

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THAT'S BECAUSE LIVING IN SPACE

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IS A COMPLETELY DIFFERENT
EXPERIENCE

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THAN LIVING HERE ON EARTH,

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AND IT HAS
SOME INTERESTING EFFECTS

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ON THE ASTRONAUTS' BODIES.

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FIND OUT MORE ABOUT
THEIR HEART-PUMPING ADVENTURES,

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NEXT ON "REAL WORLD."

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YOU PROBABLY ALREADY KNOW
THAT WHEN IN ORBIT,

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ASTRONAUTS' BODIES STRETCH,

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AND THEY LOSE
BONE AND MUSCLE MASS.

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BUT THOSE AREN'T
THE ONLY PHYSICAL EFFECTS

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THE ASTRONAUTS
HAVE TO PREPARE FOR.

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LET'S HEAR ABOUT SOME OTHER
KINDS OF PHYSIOLOGICAL CHANGES

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FROM CANADIAN SPACE AGENCY
ASTRONAUT BOB THIRSK,

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ON BOARD
THE INTERNATIONAL SPACE STATION.

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- DURING SPACEFLIGHT,
OUR HUMAN BODIES

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HAVE TO ADAPT
TO THIS NEW, UNUSUAL

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LIVING AND WORKING ENVIRONMENT
OF SPACEFLIGHT.

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WEIGHTLESSNESS AFFECTS EACH
OF OUR PHYSIOLOGICAL SYSTEMS,

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INCLUDING
OUR SENSORY-MOTOR SYSTEM.

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IN ADDITION,
SPACEFLIGHT IS NOT EASY.

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IT PLACES SIGNIFICANT
COGNITIVE DEMANDS

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UPON THE ASTRONAUT CREW.

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- COGNITIVE,

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OR BASICALLY
THE PROCESS OF THOUGHT.

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COME ON, OUT THERE.

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IF SOMEONE HAS EVER TOLD YOU
TO TURN ON YOUR BRAIN,

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THEY'RE TALKING
ABOUT COGNITIVE PROCESSES.

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- ASTRONAUTS SPEAK
OF A CERTAIN MUDDINESS

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OF COGNITIVE THINKING PROCESS

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DURING THE FIRST FEW DAYS
OF SPACEFLIGHT.

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IT SEEMS THAT FOR THE FIRST
FEW DAYS AFTER WE ARRIVE

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THAT WE'RE JUST NOT
QUITE AS SHARP

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AS WE WERE ON THE GROUND.

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WELL, NEUROLOGICAL AND THINKING,
OR COGNITIVE, PROCESSES

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CAN BE STUDIED BY MEASURING
SIGNALS FROM THE BRAIN

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AND FROM THE PERIPHERAL
NERVOUS SYSTEM.

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THAT'S THE REASON
WHY WE WEAR THIS AMUSING HAT.

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WITHIN THE HAT,
THERE ARE 54 ELECTRODES

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THAT MONITOR OUR BRAIN WAVES,
OR EEG SIGNALS.

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IT ALSO CONTAINS ELECTRODES
THAT MONITOR EYE MOVEMENTS.

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ELSEWHERE ON OUR BODY,
WE WEAR SENSORS

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THAT MONITOR MUSCLE MOVEMENT
IN OUR HANDS

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AND ALSO OUR CARDIAC RHYTHM
AS WELL.

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- YOU EVER NOTICE HOW ASTRONAUTS
LOOK ALL PUFFY IN THE FACE

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WHEN THEY FIRST
GO INTO ORBIT?

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WELL, LET'S CHECK IN
WITH BOB AGAIN TO FIND OUT WHY.

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- ON EARTH, OUR HEART
PUMPS OXYGEN-RICH BLOOD

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UP TO THE BRAIN,

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AND THEN EARTH'S GRAVITY
HELPS PULL THE BLOOD

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BACK DOWN TO THE LOWER PARTS
OF THE BODY.

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SINCE THE BRAIN IS THE CAPSTONE
OF OUR PROVERBIAL PYRAMID,

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OUR HEART HAS TO WORK
ESPECIALLY HARD

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TO PUMP BLOOD UP TO IT.

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BUT IN WEIGHTLESSNESS,
THERE IS A DIFFERENCE.

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THE BLOOD VOLUME IN OUR HEAD
AND CHEST INCREASES.

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FOR THOSE OF YOU WHO KNOW ME,

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YOU RECOGNIZE THAT MY FACE
IS NOW ROUNDER AND PUFFIER

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THAN TYPICAL ON EARTH.

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ANYWAYS, THIS INCREASED
CENTRAL BLOOD VOLUME IN SPACE

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REDUCES THE WORKLOAD
OF THE HEART.

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THIS DOESN'T POSE A CHALLENGE
TO OUR HEALTH WHILE IN SPACE,

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BUT IT CAN HAVE
NEGATIVE CONSEQUENCES

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ONCE WE'RE BACK ON THE GROUND.

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- [breathing heavily]

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BASICALLY, THE HEART
DOESN'T HAVE TO DO AS MUCH WORK

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TO PUMP BLOOD WHEN ON ORBIT.

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YOU MIGHT SAY IT GETS LAZY.

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TO UNDERSTAND
JUST HOW THAT HAPPENS,

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WE HAVE TO KNOW A LITTLE BIT
ABOUT BLOOD FLOW.

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CARDIAC OUTPUT IS THE AMOUNT
OF BLOOD IN MILLILITERS

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PUMPED BY THE HEART
IN ONE MINUTE.

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ON EARTH AND IN SPACE,

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DIFFERENT CONDITIONS
CAN CHANGE CARDIAC OUTPUT.

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TO FIND CARDIAC OUTPUT,
WE USE MULTIPLICATION.

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CARDIAC OUTPUT, OR MILLILITERS
OF BLOOD PER MINUTE,

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EQUALS STROKE VOLUME,
IN MILLILITERS PER BEAT,

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TIMES HEART RATE,
BEATS PER MINUTE.

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ON EARTH, STROKE VOLUME IS ABOUT
75 MILLILITERS PER BEAT.

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AN AVERAGE ADULT'S PULSE RATE
IS ABOUT 70 BEATS PER MINUTE.

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IF WE MULTIPLY
75 MILLILITERS PER BEAT

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TIMES 70 BEATS PER MINUTE,

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WE FIND THAT AN AVERAGE
CARDIAC OUTPUT

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WOULD BE AROUND
5,250 MILLILITERS PER MINUTE.

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WE KNOW THAT 1,000 MILLILITERS
MAKE UP A LITER,

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SO ABOUT 5.25 LITERS OF BLOOD

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ARE PUSHED THROUGH THE HEART
EACH MINUTE.

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WE ALSO KNOW
THAT THE HUMAN BODY

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HOLDS ABOUT FIVE LITERS
OF BLOOD.

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THAT MEANS
THAT IN A MINUTE'S TIME,

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ALL OF THE BLOOD IN THE BODY
IS PUMPED THROUGH THE HEART.

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BUT WHAT ABOUT CARDIAC OUTPUT
IN SPACE?

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THE POOLING OF FLUID
IN THE UPPER PART OF THE BODY--

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THAT PUFFY HEAD STUFF
BOB THIRSK WAS TALKING ABOUT--

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SIGNALS THE HEART
TO PUSH MORE BLOOD

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THROUGH THE HEART
WITH EACH BEAT.

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AS A RESULT,
THE ASTRONAUT'S STROKE VOLUME

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IS INCREASED TO ABOUT
90 MILLILITERS PER BEAT.

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BUT SOMETHING ELSE HAPPENS
IN MICROGRAVITY

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WHEN THE BODY
SENSES THE EXTRA BLOOD

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IN THE UPPER BODY.

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IT INTERPRETS THE POOLING BLOOD
AS TOO MUCH FLUID,

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SOMETHING CALLED OVERHYDRATION.

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THIS SIGNALS THE KIDNEYS

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TO REMOVE THE WATER
FROM THE BLOOD

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AND GET RID OF IT AS URINE.

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AFTER ONLY ONE DAY
BEYOND EARTH'S GRAVITY,

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ASTRONAUTS
HAVE A LOWER BLOOD VOLUME.

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THEY CAN LOSE AS MUCH
AS 20% OF THEIR BLOOD VOLUME

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WHILE ON A SPACE MISSION.

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SINCE THE BODY HAS LESS BLOOD
TO PUSH AROUND

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AND THE HEART IS PUSHING
MORE BLOOD WITH EACH BEAT,

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AN ASTRONAUT'S HEART RATE
ALSO SLOWS DOWN TO COMPENSATE.

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ASTRONAUTS
JUST DON'T NEED AS MUCH BLOOD

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IN THE ENVIRONMENT OF SPACE,

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AND THE HEART
JUST DOESN'T WORK AS HARD

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TO MOVE THE BLOOD
THROUGH THE BODY,

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SO AN ASTRONAUT'S HEART RATE
AND BLOOD PRESSURE

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ARE CAREFULLY MONITORED BEFORE,
DURING, AND AFTER MISSIONS.

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AND ASTRONAUTS
TAKE SPECIAL COUNTERMEASURES,

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LIKE EXERCISING
AND DRINKING LOTS OF FLUIDS

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JUST BEFORE RETURNING TO EARTH,

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TO HELP THEIR BODIES
RETURN TO NORMAL.

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SO THE NEXT TIME
YOU TAKE YOUR PULSE,

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THINK ABOUT THE DOCTORS, NURSES,
AND MEDICAL TECHNICIANS

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WHO ARE MONITORING
THE ASTRONAUTS,

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KEEPING THEM HEALTHY IN SPACE.

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I'LL SEE YOU NEXT TIME
ON "REAL WORLD."