Hypertension means high blood pressure. Blood pressure is the force that pushes blood through the vessels. Systolic pressure occurs as the left ventricle pushes the blood out of the heart; it represents the greatest amount of pressure within the arteries at any one time. Diastolic pressure occurs while the heart is resting; it represents the least amount of pressure in the arteries at any one time. The heart rate, the force of the heart’ contraction, the viscosity of the blood, and the degree of dilation or constriction of the arterioles determines the blood pressure.

Hypertension increases oxidative stress inside the body. It damages the insulation of the nerves and contributes to cognitive decline. Because it pushes cholesterol into the arteries, it increases the risk for coronary disease and stroke. It also increases the risk for metabolic syndrome, insulin resistance, kidney damage, and blindness.

The nervous system plays an extremely important role in regulating blood pressure. How does it do so?

Sympathetic Nerves

The nervous system helps to regulate the blood pressure through the sympathetic nerves. Sympathetic activation speeds the heart rate and force of contraction and constricts the arteries; this causes the blood pressure to increase. Parasympathetic activation, on the other hand, slows the heart rate. Not only does activation of sympathetic nerves increase heart rate, but it also constricts the blood vessels. In hypertension, the sympathetic nerves are over-stimulated. Caffeine and nicotine amplify these effects. Overeating, obesity, metabolic syndrome, sleep deprivation, and fibromyalgia all increase sympathetic activity. Fortunately, regular exercise, moderate salt restriction and wise calorie restriction all decrease sympathetic activity in obese individuals.

Baroreceptors

Baroreceptors are sensory nerve endings that are stimulated by pressure changes in the walls of blood vessels. They monitor blood pressure and notify the brain to adjust it accordingly. The most sensitive baroreceptors are located in the aorta and in the right and left internal carotid arteries that supply blood to the brain.

A baroreceptor reflex, or baroreflex, is one of the body’s mechanisms for keeping blood pressure within its normal limits. It provides an automatic negative feedback loop so that an elevated blood pressure reflexively causes the blood pressure to decrease. Similarly, a low blood pressure also signals the brain. The brain, via the sympathetic nerves, then initiates activities that cause the blood pressure to rise. In other words, the baroreflex causes sympathetic inhibition if the blood pressure does too high and sympathetic stimulation if the blood pressure falls too low.

The baroreflex works with the sympathetic nerves to regulate the body’s blood pressure. Whenever blood vessels, especially the arterioles, are constricted, the resistance to blood flow increases and blood pressure rises. Unfortunately, after two days of high blood pressure, the baroreceptors reset their “normal” point so that they consider the high blood pressure to now be normal.

Baroreflex sensitivity refers to how well the baroreceptors work. In hypertension baroreflex sensitivity is diminished and is associated with increased mortality (particularly from sudden cardiac death) following myocardial infarction. Obesity, smoking, and sleep deprivation are also lifestyle factors that decrease baroreflex sensitivity. Fortunately, moderate exercise, an optimal amount of sleep, wise calorie restriction, and consumption of cashews all improve it.

Mental Health and Blood Pressure

Attitudes greatly influence blood pressure. For example, hostility and a high level of stress coupled with impatience make the risk for developing high blood pressure six to eight times greater.

Chronic anxiety contributes to chronic activation of the sympathetic nerves. So do chronic stress, social isolation, and hostility. These conditions each contribute to increased sympathetic tone which means a faster heart rate, more vasoconstriction, and elevated blood pressure. These attitudes are more detrimental in individuals with hypertension or diabetes, because the sympathetic nerves are already overstimulated.

According to Dr. Brian Curtis and Dr. James O’Keefe, Jr. in their article“Autonomic Tone as a Cardiovascular Risk Factor,” exercise, social support, faith, sleep, weight loss (if overweight), and smoking cessation improve the function of the autonomic nervous system so that there is less sympathetic influence, and more parasympathetic influence. As a result, the risk for hypertension decreases and the chance of lowering elevated blood pressure increases.

Depression, in many cases, decreases baroreflex sensitivity. Depression is also associated with elevated heart rate and stress hormones like norepinephrine. A history of major depression is a potent, independent risk factor for cardiovascular events.

Both chronic anxiety and hostility decrease baroreflex sensitivity, that is, how well the baroreceptors work. In hypertension the baroreflex is already diminished. Studies show that women, but not men, with post-traumatic stress disorder have diminished baroreflex sensitivity. The good news is that genuine happiness can protect us from some of the detrimental effects that the sympathetic nervous system and stress in general have on our cardiovascular system.

Dr. A. Steptoe and associates collected data from middle-aged men and women. They found that independent of age, socioeconomic status, smoking, body mass and psychological distress, happy individuals had lower salivary cortisol both on working and nonworking days, reduced fibrinogen stress responses, and in men, a lower ambulatory heart rate. Happiness was inversely related to ambulatory systolic blood pressure on follow-up. In other words, happiness can reduce the stress hormone cortisol, and the risk for clotting, slow the heart rate, promote better nourishment of the heart muscle, and help to protect us from high blood pressure.

 

Bibliography

  1. Alvarez, G.E., Weight loss increases cardiovagal baroreflex function in obese young and older men. Am J Physiol Endocrinol Metab, 289(4):E665, 2005.
  2. Curtis, B., and O’Keefe, J. Jr., Autonomic Tone as a Cardiovascular Risk Factor.
  3. Hall, E., Healthy Arteries, Journal of Health and Healing, 25(2).
  4. “National Institute of Health NHLBI Study Finds, Hostility, Impatience Increase Hypertension Risk. Impatience and hostility – two hallmarks of the“type A” behavior pattern – increase young.”:http://www.nhlbi.nih.gov/new/press/03-10-21.htm
  5. Schutte, A.E., Modulation of baroreflex sensitivity by walnuts versus cashew nuts in subjects with metabolic syndrome. Am J Hypertens, 19(6):637-638, 2006.
  6. Steptoe, A., Positive affect and biological function in everyday life. Neurobiol Aging, 26 Suppl 1:108-112, 2005.
  7. Straznicky, N.E., Effects of dietary weight loss on sympathetic activity and cardiac risk factors associated with the metabolic syndrome. J Clin Endocrinol Metab, 90(11):5998-6005, 2005. Epub, Aug 9, 2005.
  8. Takeshita, Y., et al., Cross talk of tumor necrosis factor-alpha and the renin-angiotensin system in tumor necrosis factor-alpha-induced plasminogen activator inhibitor-1 production from hepatocytes. Eur J Pharmacol, 2007, 2008 Jan 28;579(1-3):426-32.