710
UNIT 4
Maintenance of the Body
19
Tese pulse points are also called
pressure points
because
they are compressed to stop blood flow into distal tissues during
hemorrhage. For example, if you seriously lacerate your hand,
you can slow or stop the bleeding by compressing your radial
or brachial artery.
Monitoring pulse rate is an easy way to assess the effects of
activity, postural changes, and emotions on heart rate. For ex-
ample, the pulse of a healthy man may be around 66 beats per
minute when he is lying down, 70 when he sits up, and 80 if he
suddenly stands. During vigorous exercise or emotional upset,
pulse rates between 140 and 180 are not unusual because of
sympathetic nervous system effects on the heart.
Measuring Blood Pressure
Most o±en, you measure systemic arterial blood pressure in-
directly in the brachial artery of the arm by the
auscultatory
method
(aw-skul
9
tah-to
0
re). Te steps of this procedure are
outlined next:
1.
Wrap the
blood pressure cuff
, or
sphygmomanometer
(sfig
0
mo-mah-nom
9
ĕ-ter;
sphygmo
5
pulse), snugly
around the person’s arm just superior to the elbow.
2.
Inflate the cuff until the cuff pressure exceeds systolic pres-
sure. At this point, blood flow into the arm stops and a
brachial pulse cannot be felt or heard.
3.
Reduce the cuff pressure gradually and listen (auscultate)
with a stethoscope for sounds in the brachial artery.
Te pressure read when the first so± tapping sounds are
heard (the first point at which a small amount of blood is spurt-
ing through the constricted artery) is systolic pressure. As the
cuff pressure is reduced further, these sounds, called the
sounds
of Korotkoff
, become louder and more distinct. However, when
the artery is no longer constricted and blood flows freely, the
sounds can no longer be heard. Te pressure at which the
sounds disappear is the diastolic pressure.
Homeostatic Imbalances in Blood Pressure
Normal blood pressure for resting adults is a systolic pressure
of less than 120 mm Hg and a diastolic pressure of less than
80 mm Hg. ²ransient elevations in blood pressure occur as nor-
mal adaptations during changes in posture, physical exertion,
emotional upset, and fever. Age, sex, weight, and race also affect
blood pressure. What is “normal” for you may not be normal for
your grandfather or your neighbor.
Hypertension
Chronically elevated blood pressure is called
hypertension
and
is characterized by a sustained increase in either systolic pres-
sure (above 140 mm Hg) or diastolic pressure (above 90 mm Hg).
Te American Heart Association considers individuals to have
prehypertension
if their blood pressure values are elevated but not
yet in the hypertension range. Tese individuals are at higher risk
for developing full-blown hypertension and are o±en advised
to change their lifestyles to reduce their risk of developing full-
blown hypertension.
It prods the posterior pituitary to release ADH, which pro-
motes more water reabsorption by the kidneys.
It triggers the sensation of thirst by activating the hypotha-
lamic thirst center (see Chapter 26). Tis encourages water
consumption, ultimately restoring blood volume and so
blood pressure.
It is a potent vasoconstrictor, increasing blood pressure by
increasing peripheral resistance.
Clinical Monitoring of Circulatory Efficiency
Clinicians can assess the efficiency of a person’s circulation by
measuring pulse and blood pressure. Tese values, along with
measurements of respiratory rate and body temperature, are re-
ferred to collectively as the body’s
vital signs
. Let’s examine how
vital signs are determined or measured.
Taking a Pulse
Te alternating expansion and recoil of arteries during each
cardiac cycle allow us to feel a pressure wave—a
pulse
—that
is transmitted through the arterial tree. You can feel a pulse in
any artery that lies close to the body surface by compressing the
artery against firm tissue, and this provides an easy way to count
heart rate. Because it is so accessible, the point where the radial
artery surfaces at the wrist, the
radial pulse
, is routinely used to
take a pulse measurement, but there are several other clinically
important arterial pulse points
(Figure 19.12)
.
Common carotid artery
Brachial artery
Radial artery
Femoral artery
Popliteal artery
Posterior tibial
artery
Dorsalis pedis
artery
Superficial temporal artery
Facial artery
Figure 19.12
Body sites where the pulse is most easily
palpated.
(We discuss the specific arteries indicated on pp. 726–735.)
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