Introduction
Hypertension due to unknown cause or rather essential hypertension is responsible for an estimated 95% of the reported cases of hypertension. Its trend is seen in families and can be categorized as one of the genetically acquired or inheritance diseases. Numerous pathophysiological are said to causes hypertension with several experiments and research carried out to establish solid evidence. Sympathetic nervous system is one of the factors considered due to its effect on cardiovascular activities in the human body.
Blood pressure
Blood pressure is mainly as a result of vascular resistance and output of the cardiac muscles. All these actions on the human body and other animals are under the control of autonomic nervous system. The autonomic nervous system makes adjustments on blood circulation depending on the behavior, emotions of an individual, and the environment (AMERICAN SOCIETY OF HYPERTENSION 2012). The changes take place to varying the blood pressure and therefore supply the body with the necessary requirements dependent on the factors preceded. The changes also ensure a homeostatic condition for the well-being of internal and external conditions and functions of the body is attained. The main changes enacted are processed in the brain to relay information on the target organs responsible for different actions to alter the blood pressure. It is clear from this the central nervous system has a main role to play in regulating the blood pressure of a particular person.
Sympathetic efferent
Sympathetic efferent that regulate the cardiovascular activities can be classified into three wide categories based on their sensitivities. The categories are thermosensitivity, barosensitivity, glucosensitivity. The first classification, thermosensitivity, comprises of cutaneous vasoconstrictors. The vasoconstrictors can be activated by emotions, hypothermia, and hyperventilation. Many people are aware of the fight or flight hormone called the adrenaline. It is produced after the occurrence of an emotional stimulus such as fear or excitement. The second group of efferent called the gluconsensitivity group affects its production. The hormone is produced from the adrenal medulla, which is activated, by physical exercise or hypoglycaemia (BAKRIS & BALIGA 2012).
The two discussed groups are a minority with the major part of the three efferents being taken by barosensitive group. Barosensitive efferents control the kidney functions, heartbeat and subsequent heart activities, and the release of noradrenaline. This group of efferent is responsible for the short-term control of blood pressure as it is involved in response to instant occurrences in the human body and the production of the necessary secretions for the stimulation. Action of the barosenstive efferents also indicates that they affect the long-term control of blood pressure. It affects secretion of rennin, sodium reabsorption, and the renal blood flow. Action of this is seen, for example, in the case of excitement. The stimulus is in such a way that the blood pressure increases and there is an increase in oxygen amount supplied to the muscle tissues. It is the group responsible for the production of adrenaline hormone from the adrenal glands which also causes increases in oxygen supply to the muscle tissues for fight or flight.
SNS and Obesity
Obesity is a recognized problem affecting many people around the world. Health care records indicate that most obese individuals end up suffering from hypertension with the real reason not established. However, experiments performed by different scientists clearly indicate that the sympathetic nervous system has a role to play in the situation. Several factors in obesity lead to the increased SNS activity, which in turn leads to hypertension in obese individuals. These factors include; hyperleptinemia, central pro-opiomelanocortin activation, hyperinsunilemia, hypoghrelinemia, and cases baroreceptor dysfunction (NADAR & LIP 2012). The major thing noticed in obese cases is the interfered kidney function, which is due to several reasons as suggested by the experiments carried out by victor et al. The sympathetic nervous system appears in the sense that the obesity causes activation of the system by the high level of the hormone leptin derived from adiposity.
It should be noted that obesity does not lead to increased generalized sympathetic nervous system action but can sometimes lead to a differentiated or rather varied behavior of the system in different muscles. A vivid example of this is the humans where in case of obesity the SNS activities in the skeletal muscles are the ones that are elevated. Activities of the same system on the cardiac muscles are barely altered or conversely it may be reduced. The reduction occurs as a result of baroreflex inhibition. Among humans, visceral obesity displays more sympathetic nervous system activation compared to subcutaneous obesity (CHERIYAN, MCENIERY & WILKINSON 2010).
Sympathetic nervous system and Obstructive sleep apnea
Recent study indicates that 85% of the people suffering from obesity also suffer from obstructive sleep disorder. It takes place via several physiological mechanisms. Establishment of a mechanism that completely gives a relationship between obsessive sleep apnea and cardiovascular disorder has been a subject under research for quite some time with conclusive reports yet to be given. Nevertheless, there is substantial evidence indicating that autonomic mechanisms in the human body are affected by this condition. A consistent observation of those suffering from the condition show that increased SNS activity is recorded (EGAN & LACKLAND 2011). When an individual is sleeping, repetitive cases of hypoxia, obstructive apnoea, and hypercapnia that acts through a combined reflex action of the chemoreceptor and other mechanisms to increase the activity of the sympathetic nervous system. The major occurrence is the activation by the pulmonary stretch receptors that are usually inactive when an individual is sleeping.
Surprisingly, the condition can happen even during daytime when the victim is fully awake and experiencing normal breathing rate and heartbeat rates. Increased sympathetic activity and pressure of the blood may also be because of humoral and neural mechanisms in different parts of the body especially the brain and central nervous system that affect the cardiovascular activities. Positive airway pressure treatment for an extended period for OSA patients produce good results but requires care and attention while administering the process considering the healing pattern of the patient. In the US, most of the OSA conditions go undiagnosed, and the result is alarming. It leads to metabolic abnormalities and even worse cardiovascular derangements, which in one way or the other causes obesity. From the preceded discussion on obesity, it is clear that it causes hypertension through other factors besides increasing the sympathetic nervous activity.
Excess of Aldosterone
Intensive research over an extended period indicates that aldosterone is highly involved in cases of hypertension in some patients. Presence of the increased level of aldosterone on the central nervous system leads to the activation of the sympathetic nervous system in different regions or other words increased activities of the cardiovascular muscles. Such cases of activation of the SNS on the cardiac muscles and the kidney secretions may lead to the situation of hypertension. In an attempt to determine the truth lying behind this possible occurrence an experiment with administration of aldosterone blocker, indicates that a stable state or rather reduced level of hypertension is attained after a period. Technical analysis of this situation shows that there is a change on a factor or factors that affect the autonomic activities of the human body (EUROPEAN SOCIETY OF HYPERTENSION, & INTERNATIONAL SOCIETY OF HYPERTENSION 2010).
Clearer concept of aldosterone activation of the sympathetic nervous system can be achieved by considering the mineralocorticoid receptors (WEIR 2005). It is usually expressed in many cells and specific types of neurons. The receptors that are available in the periventricular nuclei are highly involved in neural activity and thus directly affect the SNS activation mechanism.
The physicians to try to establish a long lasting solution for the condition are still carrying on research work and experiments. One of the experiments is one done by researchers in college of cardiology in America. It was performed to determine the effects of nitrendipine and enalapril on the action of cardiac sympathetic nervous system. Metaiodobenzylguanidine method is utilized for cardiac analysis and taking of measurements after regular intervals. After a period and the analysis of several patients subjected to the two available drugs at different doses, it was discovered that enalapril was able to reduce the activities of the sympathetic nervous system (MACGREGOR & KAPLAN 2010). Patients who were subjected to various doses of nitrendipine did not show a positive response in terms of reduction of the activities by the sympathetic nervous system.
Conclusion
In conclusion, hypertension is very serious condition, and the rate at which people are being affected by this condition is increasing. According to the rate of reported cases of this condition, it is estimated that by the year 2050, 16 million will be affected by this conditions. It is the duty of the government and not only in America, but all around the world to create awareness about this dangerous condition affecting many people around the world. The situation about obstructive sleep apnea with a record statistics of 65% unnoticed cases are dangerous. Measurement techniques and instruments should be formulated and make it mandatory for every patient to undergo hypertension or blood pressure checkup regardless of the illness in question. More investments should be made on research facilities to come up with better treatment and detection method. Public awareness on feeding habits and staying healthy is crucial in ensuring that a case of obesity that leads to hypertension is reduced.
References
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AMERICAN SOCIETY OF HYPERTENSION. (2010). The journal of clinical hypertension. Darien, CT, Le Jacq Communications.
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CHERIYAN, J., MCENIERY, C., & WILKINSON, I. (2010). Hypertension. Oxford, Oxford University Press. http://search.ebscohost.com/login.aspx?direct=true&scope=site&db=nlebk&db=nlabk&AN=467532.
EGAN, B., & LACKLAND, D. T. (2011). Hypertension. Glendale, CA, Audio-Digest Foundation.
EUROPEAN SOCIETY OF HYPERTENSION, & INTERNATIONAL SOCIETY OF HYPERTENSION. (2010). Journal of hypertension. [Philadelphia], Lippincott Williams & Wilkins. http://www.jhypertension.com/.
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THE JAPANESE SOCIETY OF HYPERTENSION. (2011). Hypertension research. http://www.jstage.jst.go.jp/browse/hypres/-char/en.
WEIR, M. R. (2005). Hypertension. Philadelphia, American College of Physicians.
