Vasoconstriction (definition) is defined as the narrowing of blood vessels usually implying arteries and arterioles. Blood flow in these blood vessels can get restricted due to 3 major causes:
– a spasmodic state of the smooth muscles due to hypocapnia and other causes
– an inflammation of blood vessels
– accumulation of cholesterol and other chemicals on walls of blood vessels.
Among common effects of constriction of blood vessels are cold hands and feet, angina pain (as during heart attacks), constipation, cramps and many others.
The most potent known vasodilator is CO2 (see Vasodilation for clinical studies). Smooth muscles of mammals are highly sensitive to arterial CO2 levels. Thus, spasm in the smooth muscles of arteries and arterioles is a normal physiological reaction to hypocapnia.
We know the alterations with angiotensinogen II and renin-angiotensin-aldosterone system (RAA) are what cause vasoconstriction as such. In theory, the first cause of vasoconstriction is essential, which is the primary cause of high blood pressure.
The key cause of vasoconstriction
Vasoconstriction is common in most modern people due to arterial hypocapnia caused by chronic habitual overbreathing. The major cause of overbreathing is a myth that breathing more air provides more oxygen for body cells and the fact that over 90% of people breathe at rest much more air than the medical norm (see the Homepage for images and clinical studies).
People with heart disease, cancer, diabetes and many other conditions have even heavier breathing (see the Homepage for over 50 clinical studies), lower arterial CO2 and more problems with vasoconstriction. A small group of patients with COPD-related conditions have elevated carbon dioxide levels in the blood caused by ventilation perfusion mismatch. These people suffer from arterial hypercapnia due to low CO2 in their airways.