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TAKING A PULSE

Area of Science:

Biological Sciences


Grade 4-6 (age 8-10).


Overview:
Take your pulse at mutliple sites. Relate the pulse to heartbeat.

Equipment:
Clock or watch
a diagram of the body
a stethoscope may be helpful.

Safety:
When taking the carotid pulse in the neck, be certain to take one side at a
time!

How to do the experiment:
Try taking your pulse at the following sites:

* Radial Pulse: This is probably what we're most familiar with when visiting
the doctor's office. Take two fingers, preferably the 2nd and 3rd finger, and
place them in the groove in the wrist that lies beneath the thumb. Move your
fingers back and forth gently until you can feel a slight pusation - this is
the pulse of the radial artery which delivers blood to the hand. Don't press
too hard, or else you'll just feel the blood flowing through your fingers!
You can even use your thumb.
* Carotid Pulse: The carotid arteries supply blood to the head and neck. You
can feel the pulse of the common carotid artery by taking the same two finger
and running them alongside the outer edge of your trachea (windpipe). This
pulse may be easier to find that of the radial artery. Since the carotid
arteries supply a lot of the blood to the brain, it's important not to press
on both of them at the same time!
* femoral pulse: The femoral atery carries blood to parts of the leg. Aside
from the carotid artery, it is another common site to check for a pulse in an
emergency situation. Think of an imaginary line running from your hip to the
groin. The approximate superficial location of the femoral artery lies 2/3 of
the way in from the hip. Admin note: the other following sites can also be
tried:

 

1. facial artery: Gently run a finger along the lower edge of the jaw bone.
Just beyond the 'chin' on either side, you might be able to feel the pulse
of the facial artery.
2. brachial artery: Flex your bicpes muscle. Press your thumb or a few
fingers into the groove created between the biceps and other muscles,
approximately 5cm from the armpit. You should be able to feel the pulse of
the brachial artery. This is the major artery supplying blood to the arms.
3. Abdominal aorta: Very thin individuals may be able to note a slight
pulsation beneath the stomach when lying down in a relaxed position. This
pulsation is caused by the abdominal aorta, the continuation of the aorta
from the heart. At the level of the umbilicus (belly button), the aorta
splits into the left and right common iliac ateries which deliver blood to
the legs.
4. Popliteal atery: This artery lies behind the knee. Bend your knee slightly
and feel in the soft area behind the knee.

Explanation:
The pulse represents the beating of the heart, specifically the ejection of
blood from the left ventricle to the general circulation of the body. The
ventricles (right and left) have two phases: diastole or the time when the
ventricles 'rest' so they can fill with blood, and systole, the time when the
ventricles contract to send blood either to the lungs (from the right side of
the heart), or to the rest of the body (from the left side of the heart).
Blood from the left side of the heart first enters the aorta, the largest
artery in the body. The aorta branches into smaller arteries which carry
blood to all part of the body.

The pulse represents the variation in blood pressure from diastole to
systole. During diastole blood pressure falls, but increases after systole as
the heart pumps more blood into the arteries. You feel this difference when
taking your pulse. Doctors use a device called a sphygmomanometer (blood
pressure cuff) to measure the systolic and diastolic blood pressures. The
average adult has a systolic blood pressure ~120-150 mm mercury, an average
diastolic blood pressure ~80 mm mercury, and an average pulse of 72
beats/minute.

If you have a stethoscope try listening to your heart while taking your
pulse. Your heart produces two sounds, often called 'lub' and 'dub.' The
second,'dub' sound coincides with the ejection of blood from the ventricles
In actuality, the sound is produced by the aortic and pulmonic valves closing
behind the ejected blood. The aortic valve opens from the left ventricle into
the aorta; the pulmonic valve from the right ventricle into the pulmonary
artery.