The Central Nervous System Feedback System and Blood Pressure
Monday, Dec 10 2007
The brain and circulatory system also make use of important feedback systems that assist in directing which elements of the neuroendocrine, renal, or autonomic nervous systems should be activated (see baroreceptor feedback system in Figure 1.2). Located along portions of the carotid artery and the aorta are several hundred pressure detectors called baroreceptors. These specialized cells operate like ‘stretch’ detectors that respond to alterations in blood pressure in the arteries and send neural signals to the brainstem to inform the brain which component of the autonomic nervous system should fire (Kezdi, 1977). For a properly functioning baroreceptor, increased blood pressure should lead to firing the parasympathetic nervous system and an immediate drop in heart rate. To the contrary, inadequate blood pressure should result in a signal to increase either heart rate or vasoconstriction via the sympathetic nervous system.
There are various elements of the central nervous system involved in this feedback system, including the brainstem, the hypothalamus, and other components of the limbic system. It is known that activation of baroreceptors results in activity in the upper medulla called the nucleus of tractus solitarius, which is a portion of the brain that regulates vagal tone (Lovallo, 1997).
Stimulation of this group of neurons leads to increased parasympathetic activity, and deactivation results in labile blood pressure (DeJong et al., 1977). Blood pressure is also regulated by cortical mechanisms other than those in the brainstem. For example, stimulation of parts of the hypothalamus and other portions of the limbic system has been shown to result in blood pressure responses (Folkow and Van Euler, 1954; Gebber and Klevans, 1972).
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 contrast to the relatively few mechanisms influencing water pressure in a hydraulic water-pumping system, it should be evident that a multitude of factors interact with one another to influence blood pressure. Not only do the factors outlined above contribute to an organism’s current blood pressure, but they also influence one another (for example, the hypothalamus affects kidney function via the neuroendocrine system), and these interactive effects further complicate the identification of mechanisms causing a specific elevation in blood pressure. Given the integrated system outlined, it is possible that no single mechanism is responsible for conditions of high blood pressure for every hypertensive patient. Perhaps different physiological mechanisms involved in the regulatory system result in dysfunctions in blood pressure regulation among different patients. Elevated blood pressure, then, may represent the final common pathway that results from a variety of underlying physiological disturbances.
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. Woodring Black, M.D.
Provided by Armina Hypertension Association
Also in this section
- 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
- New research may boost drug efficacy in treating pulmonary arterial hypertension
- Borderline high blood pressure tied to deaths
- New hypertension guidelines offer practical, clinical information for doctors and patients
- For black men, early household linked to blood pressure
- Hypertension improvement program associated with increase in blood pressure control rates
- Teens with high blood pressure have less distress, better quality of life
- High blood pressure in young adults likely to go undiagnosed
- New medication shows promise as lipid-lowering therapy for rare cholesterol disorder
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.