women has evolved differently than in men, primarily due to their monthly ovu-
latory cycle and the need to retainfluid volume for uterine egg implantation. This
hidden adaptation makes their blood pressure less sensitive to dietary salt and tends
to protect them from cardiovascular insults during their reproductive years. Finally,
there is also a venous blood pressure adaptation in humans, made necessary as we
became bipedal. The soleus muscle pump which is initiated by neuronal signals
from Meissner’s corpuscles located on the plantar surface of the foot generates the
added venous blood pressure needed to counteract the effects of gravity on the 70–
75% of blood volume that is below the heart when humans stand.
A large part of this discussion has been focused on the functional aspects of
blood pressure, as it occurs in relation to how people in Western societies behave. It
is highly likely that the blood pressure and underlying hormonal responses to the
different physical and cultural environmental circumstances in non-Western pop-
ulations will be different, although surprisingly, there are relatively few studies of
ambulatory blood pressure and behavior in these populations. Thus, for example,
the examination of sociological roles on circadian blood pressure patterns as I have
described them here is likely idiosyncratic and ethnocentric to the populations
studied. However, there have been studies in migrant populations such as Filipinos
living in Hawaii (see Brown, this volume).
Finally, there are“hidden”physiological adaptations in populations that relate to
climate that might also affect the“hidden”blood pressure adaptations noted in the
current discussion (James 2013 ). Readers interested in these should consult James
and Baker ( 1995 ) or James ( 2013 ). However, suffice it to say that all physiology is
integrated, so that the blood pressure responses to thermal, postural, dietary,
reproductive, and physical stressors are interrelated. One might say that this
interconnectedness is also part of the“hidden adaptability”of blood pressure.
Acknowledgments Some of the data reported were collected from studies supported by NIH
Grants HL37054, HL47540, and CA72457.
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164 G.D. James