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Let's Get Pumped!
Experiment #4
Air date: 2/19/98
OBJECT: To test the connection between the heart and body position
or movement.
| WHAT YOU'LL NEED: |
stopwatch
paper
pen or pencil
|
| WHO YOU'LL NEED: |
4 people:
- subject
- pulse-taker
- timer
- recorder
|
WHAT YOU NEED TO KNOW:
Your heart is the pump that moves blood through your body. The tightening
and relaxing of the heart muscle is called a heartbeat. The heart pumps
red blood cells out one valve. They circulate throughout the body and
return to the heart through another valve. Red blood cells may make that
round-trip journey through your body more than a thousand times a day
every day of your life!
 [click on image to see larger
version]
The flow of blood in the body is directly influenced by gravity. When
you're standing, gravity helps to pull the blood downward to the lower
part of the body. As you move, muscles in your legs help send the blood
back up to the heart and lungs. Without gravity, blood tends to collect
around the heart and in the upper part of the body.
The amount of blood pushed through the heart by each heartbeat is called
the stroke volume. Although stroke volume increases with activity, it
usually remains relatively stable. For this experiment, we'll assume stroke
volume is constant at about 75 milliliters per beat.
Cardiac output is the amount of blood pumped by the heart in a unit
of time. Different conditions affect cardiac output on Earth and in space.
Since cardiac output changes it is called a variable.
| Cardiac Output |
= |
stroke volume |
x |
heart rate |
| (ml/min) |
| (ml/beat) |
| (beats/min) |
On Earth, do you think changes in body position or increases in movement
can affect cardiac output?
WHAT TO DO:
Develop a one-sentence hypothesis.
Subject sits in a chair for 2 minutes.
Using the index and middle finger, pulse-taker locates the subject's
pulse by applying light pressure to the wrist to measure heartbeat.
At a cue from the timer, the pulse-taker counts the number of heartbeats
in 30 seconds, multiplies the number by two and reports the heartbeats
per minute to the recorder.
Subject stands for 1 minute, then remains standing for an additional
30 seconds while pulse-taker counts the number of heartbeats, multiplies
that number by 2, and reports the heartbeats per minute to the recorder.
Subject sits until returning to a sitting pulse rate.
Subject does a headstand against the wall (with teacher holding legs
for support) for 30 seconds, then remains in a headstand for 15 seconds
while pulse-taker counts the number of heartbeats, multiplies the number
by 4, and reports the heartbeats per minute to the recorder.
Subject sits until returning to a sitting pulse rate.
Subject jogs in place for 30 seconds and remains standing for an additional
15 seconds while pulse-taker counts the number of heartbeats, multiplies
the number by 4, and reports the heartbeats per minute to the recorder.
If more than one subject perform this experiment, use the enclosed
tally sheet to record
results. Calculate the averages.
Record average results on reply card and return to
WHAT'S IN THE NEWS, Wagner Annex, University Park, PA 16802.
To view video clip click on "Try This"
Download
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Reply card
Printable copy
Let's Get Pumped!
Hypothesis:
|
|
| Pulse rate |
| Cardiac output |
|
| Sitting |
Standing |
Inverted |
Jogging |
| . |
. |
. |
. |
| . |
. |
. |
. |
|
| CO |
= |
75 |
x |
HR |
| (ml/min) |
| (ml/beat) |
| (beats/min) |
The results of this investigation:
______ support the hypothesis
______ refute the hypothesis
______ are inconclusive
Graphic created by Medical Illustrator Howard Bartner,
contained in HUMAN PHYSIOLOGY IN SPACE, by Barbara F. Lujan and Ronald
J. White.
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