The Role of the Nervous System in Blood Pressure
Monday, Dec 10 2007
Many fluctuations in blood flow occur as a result of alterations in signals the circulatory system receives from the nervous system. As depicted by the solid arrows in Figure 1.2, the brain communicates with various organs in the circulatory system through the autonomic nervous system. This system is comprised of two separate systems called the sympathetic nervous system and the parasympathetic nervous system.
The former directs what is frequently called the ‘fight-flight’ response, and the latter directs what has been called the ‘relaxation response.’ Although initially it was thought that these two systems were interconnected (as sympathetic nervous system activity increases, parasympathetic activity decreases), it is now known that they can operate independently. In this regard, sympathetic and parasympathetic influences can work simultaneously to affect the target organs in the body.
The sympathetic nervous system employs two distinct neural systems that affect blood pressure, known as the alpha-adrenergic and beta-adrenergic systems. The alpha-adrenergic neurotransmitters and receptor systems affect blood vessels by causing them to constrict, whereas the beta-adrenergic system affects both the heart and the blood vessels. Beta-adrenergic activity leads to increased heart pumping action (increased heart rate) as well as vasodilation of blood vessels.
This combination of neural influences represents an adaptive response, as the increased blood flow caused by the increase in heart rate needs more space in the vasculature in order for blood pressure to be properly regulated. The parasympathetic nervous system influences only the heart via the vagal nerve, which results in slowed heart rate.
Figure 1.2. Major physiological systems involved in the regulation of blood pressure (dotted arrows represent local blood cell autoregulation; solid arrows represent neural influences; dashed arrows represent neuroendocrine influences; SNS = sympathetic nervous system).
In sum, these components of the autonomic nervous system interact to regulate blood pressure with the aim of keeping it within adaptive limits. During the type of exercise described above, heart rate will increase accompanied by vasodilation of the blood vessels in the leg muscles mediated by the beta-adrenergic system. This response pattern permits increased delivery of oxygen to the leg muscles without a concomitant alteration in local diastolic blood pressure. At the same time, blood flow to the gastrointestinal system is likely reduced via vasoconstriction, as digestion is not an important use of the body’s resources during a bout of exercise.
Larkin, K. T., and Zayfert, C.
Published with assistance from the foundation established in memory of Amasa Stone Mather of the Class of 1907, Yale College.
- Abel, J. A., and Larkin, K. T. (1991). Assessment of cardiovascular reactivity across laboratory and natural settings. Journal of Psychosomatic Research, 35, 365 - 373.
- Achmon, J., Granek, M., Golomb, M., and Hart, J. (1989). Behavioral treatment of essential hypertension: A comparison between cognitive therapy and biofeedback of heart rate. Psychosomatic Medicine, 51, 152 - 164.
- Agras, W. S., Horne, M., and Taylor, C. B. (1982). Expectation and the blood-pressure-lowering effects of relaxation. Psychosomatic Medicine, 44, 389 - 395.
- Agras, W. S., Taylor, C. B., Kraemer, H. C., Southam, M. A., and Schneider, J. A. (1987). Relaxation training for essential hypertension at the worksite: II. The poorly controlled hypertensive. Psychosomatic Medicine, 49, 264 - 273.
- Aivazyan, T. A., Zaitsev, V. P., Khramelashvili, V. V., Golenov, E. V., and Kichkin, V. I. (1988). Psychophysiological interrelations and reactivity characteristics in hypertensives. Health Psychology, 7, 137 - 144.
- al'Absi, M., and Wittmers, L. E. (2003). Enhanced adrenocortical responses to stress in hypertension-prone men and women. Annals of Behavioral Medicine, 25, 52 - 33.
- Albright, C. L., Winkleby, M. A., Ragland, D. R., Fisher, J., and Syme, S. L. (1992). Job strain and prevalence of hypertension in a biracial population of urban bus drivers. American Journal of Public Health, 82, 984 - 989.
- Davidyan, A. (1989). Emotional factors in essential hypertension. Psychosomatic Medicine, 55, 505 - 517.
- Alfredsson, L., Davidyan, A., Fransson, E., de Faire, U., Hallqvist, J., Knutsson, A., et al. (2002). Job strain and major risk factors for coronary heart disease among employed males and females in a Swedish study on work, lipids, and fibrinogen. Scandinavian Journal of Work, Environment and Health, 28, 238 - 248.
Last revised: by Dr. Shirak Vaishnian, M.D.
Provided by Armina Hypertension Association
Also in this section
- New Guidelines: Treat Obesity First
- Stroke Rounds: Aspirin Overused for Primary Prevention
- Understanding Dementia
- Alzheimer’s Disease Stages
- Daily consumption of blueberries may lower blood pressure
- Many home blood pressure monitors may be inaccurate
- Patient’s question triggers important study about blood thinners
- Study finds high protein diets lead to lower blood pressure
- High Blood Pressure Found to Boost Psoriasis Risk
- FDA panel votes against Novartis drug for acute heart failure
- CHOP researcher co-leads study finding genes that affect blood pressure
- Sequential Nephron Blockade Best Strategy in Resistant Hypertension
Post a comment [ + Comment here + ]
There are no comments for this entry yet. [ + Comment here + ]
Comments are moderated by our editors, so there may be a delay between submission and publication of your comment. Offensive or abusive comments will not be published.