Physiology of Organ Systems - Essay Example

?Physiology of Organ Systems: Nervous System in the Regulation of Blood Pressure and Blood Flow Introduction The normal body functions are regulated mostly by our central nervous system. The specific pathways of regulation are however different based on the system affected. This paper will discuss the nervous system and how it regulates blood pressure and blood flow to the different tissues of the body. Body The autonomic nervous system has a major function in managing the normal processes of the cardiovascular system with the interplay of pressure, volume, and the chemical receptor signals (Klabunde, 2005). With the alterations made in the peripheral vessels, cardiac output is elevated. Where there is a disorder within the system or during overactivity in the sympathetic nervous system, the blood pressure is often increased (Klabunde, 2005). Moreover, autonomic system imbalance may also be linked with metabolic and hemodynamic changes which can cause cardiovascular diseases. The primary organs involved in the regulation of blood pressure and blood flow to the tissues are the heart and the blood vessels or arteries (Carretero and Oparil, 2000). These organs deliver oxygen, nutrients, and hormones into the different cells of the body. Waste products from the different processes of metabolism are also eliminated from the organs of the body and then transported by the veins to later be eliminated through the kidneys and the lungs (Carretero and Oparil, 2000). Blood flows into the heart mostly guided by pressure difference, it flows out of the area where pressure is higher to where pressure is lower (Hall and Guyton, 2006). The heart is an organ which pumps blood and as it pumps, it creates the pressure within the circulatory system. The blood pressure inside the blood vessels is understood to be the force exerted by the blood into the walls of the blood vessels (Segura and Ruilope, 2007). The blood pressure of the arteries increases and decreases with each cycle or stage where the blood passes through the chambers of the heart. Blood enters the heart with a specific sequence or order (National Aeronautics and Space Administration, 2007). The heart also has four valves which control and manage the entry and exit of the blood into and out of the heart. The blood would enter the right atrium through the superior and inferior vena cavae and the right atrium would contract and the tricuspid valve would open and allow blood to enter the right ventricle (NASA, 2007). As the right ventricle contracts, the tricuspid valve closes and simultaneously, the pulmonary valve opens and blood enters the pulmonary artery which brings the blood to the lungs where it is infused with oxygen and eliminates carbon dioxide (Shibao, et.al., 2007). The blood then exits the lungs and enters the left atrium where it is pumped out into the different parts of the body. The blood vessel walls have layers of smooth muscle and such muscles as well as the heart muscles are regulated by the autonomic nervous system (Shibao, et.al., 2007). Where there is a decrease in the diameter of the blood vessel, the flow of the blood would be more difficult. The persistent decrease in diameter would increase the pressure needed to push the blood into the different cells of the body. The greater pressure is imposed on the heart which is forcing the blood into the different parts of the body (Lohmeier, et.al., 2004). As the smooth muscles would relax, there is lesser resistance and therefore less pressure needed to maintain the blood flow rates. The autonomic nervous system regulates the diameter of the blood vessels (Lohmeier, et.al., 2004). It also regulates the heart rate, increasing or decreasing it where necessary. With these processes, the autonomic nervous system is able to manage blood pressure. Maintenance of continuous blood flow to the brain and the cells of the body are carried out by the “regulation of blood pressure by the autonomic nervous system” (NASA, 2007, p. 104). The brain is the receptor of data related to pressure exerted by the blood on the arterial walls. This detection is carried out by pressure sensors on the arterial walls (Granado, et.al., 2009). These sensors are also known as baroreceptors. The sensors then send information via the nerves into the brainstem where monitoring by the autonomic nervous system is carried out, with the latter responding by adjusting pressure (Granado, et.al., 2009). In case the blood pressure decreases at specific points, the autonomic nervous system would increase the blood flow by decreasing the diameter of the arteries and by adjusting the rate and force of contraction of the heart. All these elements taken together increase the blood pressure (Granado, et.al., 2009). The processes involved in higher sympathetic nervous system activity for hypertension are complicated and include changes in the baroreflex and the chemoflex processes within the peripheral and central systems (Hall and Guyton, 2006). The arterial baroreceptors are adjusted to higher pressure for hypertension patients and such adjustment shifts back to normal as soon as arterial pressure is secured (Hall and Guyton, 2006). Moreover, a central readjustment for the aortic baroreflex for hypertensive patients is also seen usually causing suppressed sympathetic inhibition following the activation of aortic baroreceptor nerves. The baroreflex readjustment is mediated by angiotensin II (Lohmeier, et.al., 2004). Some mediators like reactive oxygen species and endothelin manage baroreceptors and assist in the persistent sympathetic management in hypertension. Studies indicate that hypertensive patients often indicate higher vasoconstriction responses to norepinephrine and normotensive processes. These patients do not manifest the usual responses to higher norepinephrine in the blood. Stress can increase the sympathetic response and persistent stress can eventually lead to enlargement of the blood vessels; this can lead to an increase in blood pressure (Lohmeier, et.al., 2004). The renin-angiotensin-aldosterone system also regulates blood pressure. Renin is an enzyme which maintains the extracellular volume and causes vasoconstriction in the arteries (Shibao, et.al., 2007). The renin breaks down the angiotensinogen to angiotensin I which is then converted by another enzyme known as the angiotensin converting enzyme (ACE) thereby producing angiotensin II which causes vasoconstriction (Hall and Guyton, 2006). The angiontensin II increases blood pressure and causes the adrenal glands to produce aldosterone which causes the kidneys to reuptake salt and water (Hall and Guyton, 2006). Increasing renin in the blood will therefore increase blood pressure. References Carretero, O. and Oparil, S., 2000. Essential hypertension. Part I: definition and etiology. Circulation, 101 (3): pp. 329–35. Granado, N., Smith, T., Swanson, G., Harris, R., et.al., 2009. Newly reported hypertension after military combat deployment in a large population-based study. Hypertension, 54: pp. 966–973. Hall, J. and Guyton, A., 2006. Textbook of medical physiology. St. Louis, Mo: Elsevier Saunders. Klabunde, R., 2005. Cardiovascular physiology concepts. London: Lippincott Williams & Wilkins. Lohmeier, T., Irwin, E., Rossing, M., Serdar, D., et.al., 2004. Prolonged activation of the baroreflex produces sustained hypotension. Hypertension, 43: pp. 306–311. National Aeronautics and Space Administration, 2007. Autonomic nervous system regulation [online]. Available at: http://teacherlink.ed.usu.edu/tlnasa/units/Brain/07.pdf [Accessed 26 February 2013]. Oparil, S., Zaman, M., and Calhoun, D., 2003. Pathogenesis of hypertension. Ann. Intern. Med. 139 (9): pp. 761–76. Segura J. and Ruilope, L., 2007. Obesity, essential hypertension and renin-angiotensin system. Public Health Nutrition 10 (10A): pp. 1151–5. Shibao, C., Gamboa, A., Diedrich, A., Ertl, A., et.al., 2007. Autonomic contribution to blood pressure and metabolism in obesity. Hypertension, 49: pp. 27–33. Read More