In this lesson, the physiological causes of high blood pressure are reviewed. The topics we are discussing here include genetics, inherited cardiovascular risk factors, sympathetic nervous system, vascular reactivity, vascular remodeling, renal microvascular disease, uric acid, arterial stiffness, the renin-angiotensin-aldosterone system, angiotensin II and oxidative stress, clinical trials of ACE inhibitors and ARBs, aldosterone, endothelial dysfunction, and endothelin.

What's the Deal?

There is no known cause of hypertension, however, scientists concede that genetics plays a definite role. In hypertensive cases, the cardiac output is normal, or elevated in some, possibly early in the disease. Therefore, the cardiac work is increased with altered renal physiology, accelerated natriuersis and reduced renal blood flow. There is normal bllod flow to most regions, with diminished renal and skin blood flow and a possible development of increased muscle flow. The plasma volume is reduced, possibly inversely related to diastolic pressure. Furthermore, there is hyper-reactivity of pressure to stress, abnormal vascular reactivity and impaired circulatory homeostasis.

Genetics is the study of heredity and how traits are passed along from parents to offspring.

All in the Family

Although scientists do not know which genes cause the blood pressure to vary, family studies have shown that inherited blood pressure can range from low normal blood pressure to severe hypertension. Although past research shows that the cause of essential hypertension is not known, this is only partially true because of the little information available on genetic variations. Furthermore, there is little information on the genese that are over-expressed or under-expressed as well as the intermediary phenotypes that regulate high blood pressure.

Each individual's genetic material, contained in the nucleus of each cell in the form of deoxyribonnucleic acid (DNA), is unique.

It's Relative

The “hypertensinogenic” factors that increase blood pressure include obesity, alcoholism and high sodium intake, however, some of these factors have inherited, behavioral and environmental components. Inherited blood pressure could be considered as the core blood pressure, whereas hypertensinogenic factors cause the blood pressure to rise above the range of inherited blood pressures. Furthermore, there are interactions between genetics and environmental factors that influence intermediary phenotypes such as sympathetic nerve activity, rennin angiotensin aldosterone and rennin – kallikrein – kinin systems and endothelial factors, which is in turn, influential in other intermediary phenotypes, such as sodium excretion, vascular reactivity and cardiac cartractility. These and many other intermediary phenotypes determine total vascular resistance and cardiac output and consequently, high blood pressure.