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Human Pulse and Blood Pressure Lab
*Anything in bold print should be recorded on your lab paper
In an average adult, the ventricles contract about 72 times per minute (this is the heart “beat”)
Each time they contract, about 80ml of blood is pushed out of the ventricles into the aorta and
the pulmonary artery. Contraction of the ventricles is called SYSTOLE. After each contraction
there is a period of relaxation, during which the ventricles are filled again with blood received
from the atria. This period of ventricular relaxation is called DIASTOLE. The blood forced into
the arteries during each contraction causes these vessels to expand, and this expansion can
be felt as a pulsation in the arteries near the heart such as the carotid arteries in the neck or
the radial artery in the wrist. This expansion is called the PULSE, and the number of pulses
tells you how fast the heart is beating. What is your resting heart rate as measured by
your pulse?
Since the blood is contained within a closed system, it exerts pressure against the walls
of the vessels at all times. Every time the ventricles contract, forcing blood out if the heart,
the pressure in the vessels increases; when the ventricles relax, the pressure drops again.
The pressure exerted by the blood on the walls of the blood vessels is called the BLOOD
PRESSURE. In the arteries, this pressure is sufficient to force a column of mercury upward in
a glass tube. The instrument used to determine blood pressure is called a
SPHYGMOMANOMETER, which may be of two types: the first has the column of mercury
(water or any other liquid could be used instead of mercury, but since other liquids are not as
dense as mercury, the tube used to hold the liquid would have to be impractically long); in the
second type, air pressure has been equated with mercury pressure, so that the reading on the
dial will be the same as that which would be obtained if you were using the mercury-column
type. Both types therefore measure pressure in terms of millimeters of mercury (mm Hg).
Blood pressure in the arteries will rise during each systole, and fall during diastole. The
average pressure in a young adult of average weight is aprox. 120mm of mercury during
systole, and 80mm during diastole (NOTE that this diastolic pressure indicates that even
when the ventricles are relaxed, there is pressure
exerted by the blood on the blood vessels.)
Repeated blood pressure measurements of
140/90mm Hg indicate hypertension or “high blood
pressure”.
PROCEDURE FOR MEASURING BLOOD
PRESSURE
You may use a sphygmomanometer to
measure blood pressure in your lab partner. Wrap
the pressure cuff of the sphygmomanometer snuggly
around the upper arm of your partner and follow the
instructions provided with the device or those given
by your instructor. Alternate reading each partner’s
blood pressure for 3 trials to see if you get consistent
results.
Record your results on your lab sheet in the chart below as systolic/diastolic pressure
in mm of mercury:
Student #1 (name)
Student #2 (name)
Trial 1
Trial 2
Trial 3
Indicate if you have used any
of these in the past 30
minutes.
Caffeine/Cigarettes/Exercise
Effects of Exercise on Blood Pressure
As we change our movements (either increasing or decreasing), we
can expect our blood pressure will change in response. An example of this
would be investigating what your blood pressure is after running a flight of
stairs 4 times (this would be increased activity).
1.
Make a hypothesis as to what effect activity level will have on blood
pressure.
2.
Form a data table that states 3 different levels of activity that one of
you will perform and the blood pressure readings taken after each
activity.
a. Make sure you are doing each activity for at least 2-3 minutes
so that your heart can adjust accordingly.
3.
What conclusions can you draw from your data?
4.
What explanations can you offer as to why your systolic and
diastolic pressures change in response to less/more activity?
Activity #1 - __________________________________
Student #1
Student #2
Trial 1
Trial 2
Trial 3
Indicate if you have used any
of these in the past 30
minutes.
Caffeine/Cigarettes/Exercise
Activity #2 - __________________________
Student #1
Student #2
Trial 1
Trial 2
Trial 3
Indicate if you have used any
of these in the past 30
minutes.
Caffeine/Cigarettes/Exercise
Activity #3 - __________________________
Student #1
Trial 1
Trial 2
Trial 3
Indicate if you have used any
of these in the past 30
minutes.
Caffeine/Cigarettes/Exercise
Student #2