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The mechanisms which control the blood pressure within normal limits and how drugs can be used to correct abnormalities of these mechanisms.

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Introduction

The mechanisms which control the blood pressure within normal limits and how drugs can be used to correct abnormalities of these mechanisms. Blood pressure is a measure of how hard the blood presses against the artery walls. When blood pressure is recorded, it is recorded as two numbers. The high number provides the systolic pressure and the low number provides the diastolic pressure. The systolic pressure correspond to the pressure of the arteries when the ventricles contracts. The diastolic pressure corresponds to the pressures when the arteries are at rest (after the left ventricular contraction and while the heart chambers are being refilled with blood). The Blood pressure is measured using a sphygmomanometer. There is no such thing as average (or normal) blood pressure as blood pressure differs between individuals depending on many factors. Some of the factors are: 1) age 2) Ethnicity 3) sex 4) Family history etc. There are a number of physiological mechanisms which help regulate the blood pressure within normal limits. These include Autonomic nervous system responses (Baroreceptors and chemoreceptors), Capillary shift mechanisms, vascular stress relaxation, Hormonal responses and kidney and fluid balance mechanisms. Baroreceptors (pressure sensitive nerve endings) found in the arch of the aorta and the carotid bodies detect a drop in blood pressure. The Baroreceptors send a signal to the cardiovascular centre in the brain (medulla oblongata) which causes an increase in sympathetic activity. This increase in the sympathetic activity causes an increase in heart rate and promotes vasoconstriction of both the arterial and venous side of the circulation. ...read more.

Middle

High risk hypertension can cause a number of symptoms including headache, sleepiness, confusion and coma. Hypertension is caused by a number of reasons which are classified as primary (90% of cases) and secondary (10% of cases). A primary cause is where the cause is unknown, whereas secondary causes include 1) Chronic kidney diseases 2) Chronic alcohol abuse 3) Hormonal disturbances and 4) Endocrine tumours. A number of factors can contribute to the increase in the risk of hypertension. These factors include 1) Family history 2) Obesity 3) High salt intake 4) Diabetes 5) High alcohol intake 6) kidney diseases 7) lack of exercise and 8) certain medications such as steroids. The chance of getting a cardiovascular disease is increased if an individual has hypertension as well as diabetes; therefore the targets for blood pressure control in diabetes are tighter. An individual suffering from diabetes as well as hypertension will need to have a blood pressure of less than 130mmHg (systolic) and less than 80mmHg (diastolic),whereas an individual only suffering from hypertension will need to have a blood pressure of less than 140 mmHg (systolic) and less than 85 mmHg (diastolic). Hypotension is a condition where blood circulates through the vessels at a low pressure (lower pressure than normal). When the blood pressure is low, the body organs will not have sufficient blood supply which prevents them from functioning or sometimes permanently damaging them. A common type of hypotension is orthostatic hypotension in which standing suddenly causes dizziness or even fainting. An example would be the brain not getting sufficient blood supply. ...read more.

Conclusion

Angiotensin II is responsible for a number of mechanisms that cause an increase in the blood pressure, for example it increases sympathetic activity, constriction of blood vessels and promotes the secretion of Aldestrone. When the enzyme is inhibited, Angiotensin II will not be produced from Angiotensin I thus all the mechanisms causing an increase in blood pressure will be inhibited. The major drawback in using the ACE inhibitors is that it has a major side effect, dry cough. Other side effects are also present which include an increased in potassium levels, rash, angioedema (allergic swelling that affects the face, lips, and windpipe and may interfere with breathing), and, in pregnant women, serious injury to the fetus. As discussed above, ACE inhibitors have a major side effect, dry cough. A new class of antihypertensives were developed to eliminate this major drawback. Angiotensin receptor blockers (or sometimes known as angiotensin II receptor antagonists) has the same effect as the ACE inhibitor but without the major drawback, dry cough. The way that this drug functions is different than the ACE inhibitor because the drug will not inhibit the ACE enzyme. The drug will compete with the substrate binding to the Angiotensin converting enzyme thus blocking its activity. Angiotensin receptor blockers come with a number of side effects which includes: Dizziness, an increased potassium level, angioedema (highly likely), and, in pregnant women, serious injury to the fetus. As can be seen the side effects are quite similar to the ACE inhibitor drugs but without the major side effect, dry cough (which occurs in 20% of people). Angiotensin receptor blockers include Candesartan, Eprosartan, Irbesartan, Losartan, Olmesartan, Telmisartan and Valsartan. ...read more.

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