Define how blood pressure is regulated and with reference to these factors and describe what changes would occur following an increase in blood pressure



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Summary
BLOOD PRESSURE is tightly controlled by a number of factors in the body.


DEFINE how blood pressure is regulated and with reference to these factors and DESCRIBE what changes would occur following an increase in blood pressure.
1000 words +/- 10%.
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You must include suitable references in your work and in a bibliography at the end. The deadline for this essay is 10th of March 2015

Heart is an essential organ, which acts as a pump to push and pump the blood around the body with suitable pressure. Ventricular systole is an important aspect of heart’s function. The pressure, which is put on the blood circulation, is important for the blood to reach all the essential organs of the human body to supply oxygen and other essential nutrients. It is very important for normal body function that the blood pressure is regulated in an orderly manner. The regulation of blood pressure is important to make sure that miniature blood capillaries do not burst otherwise can lead to disastrous consequences. For example if the blood capillaries which supply blood to the human brain burst due to higher pressure can lead to hemorrhage and other brain related diseases.


As mentioned above the importance of blood pressure regulation, nature has put some essential mechanisms of regulating blood pressure. There are a number of mechanisms, which regulate the blood pressure. Blood pressure depends upon the heart activity which itself affected by the activities an individual carries out for example exercise. If the heart is pumping hard in the case of exercise, it will put a higher pressure on the flow of blood, which will increase the blood pressure. The heart activity is controlled by a specialized center in the brain, which is known as the cardiovascular center. The cardiovascular center is responsible for neural mechanism because it manages the cardiac output by regulating the heart activity.

Cardiac center has two neural supplies to the heart in order to control cardiac output. The cardiac center has a sympathetic nerve supply to increase the heart rate and consequently high blood pressure however, it has also parasympathetic supply which decreases the heart rate and consequently low blood pressure. The accelerator nerve is supplied by the sympathetic and the vagus nerve is supplied by parasympathetic nervous system.

The blood vessels diameter also plays an important role in regulating blood pressure because they provide resistance to the blood flow. Blood vessels diameter can be altered to provide total peripheral resistance, which is a major regulation of blood pressure. Blood vessels are constricted to maintain higher blood pressure and vasodilation is responsible for keeping blood flow at lower pressure. Both vasoconstriction and vasodilation are controlled by neural as well hormonal mechanisms. Vasoconstriction is regulated by vasomotor center located in the brain. Nerve impulse transmission over sympathetic motor neurons or vasomotor nerves stimulate the arteriole smooth muscle to contract and maintain vasomotor tone or keep the blood vessels constricted.

Blood vessels dilation is important to lower the blood pressure.


Bradykinin is an important protein that dilates the blood vessels however the activity of bradykinin can be inhibited by another enzyme called angiotensin-converting enzyme (ACE). Angiotensin II ( vasoconstrictor) is obtained from the activity of angiotensin converting enzyme (ACE), which converts angiotensin I into angiotensin II. Angiotensin I is obtained from another protein, synthesized in the liver called angiotensinogen. Angiotensinogen is a substrate for an enzyme called renin, which is secreted, by specialized cells in the kidney called juxtaglomerular cells. Therefore kidney is an important organ in terms of secretion of renin, which is only released if low blood pressure is detected.

Angiotensin II also stimulates the secretion of aldosterone, which stimulates kidney to retain sodium ions and water to increase blood volume and pressure if low blood pressure and volume are detected. (Widmaier et al, 2007)


Moreover, there are specialized receptors known as baroreceptor and chemoreceptor, which detect low blood pressure as well as low blood volume. Chemoreceptor detects low sodium concentration of the renal tubule fluid where as baroreceptor detects low blood pressure.

Hormonal mechanism consists of special hormones known as epinephrine and norepinephrine, which increase the heart activity and thus increase the blood pressure.

All the above mechanisms are important to regulate blood pressure according to individual’s needs. For example after a vigorous exercise, the fluctuation in blood pressure is great therefore it is vital that blood pressure is controlled. Many changes take place in the body after blood pressure has increased. The first change that occurs after high blood pressure is the extra strain that is put on the heart so it can pump hard thus increases the cardiac output as well as the stroke volume. When the blood pressure is high, the blood vessels walls made of smooth muscles contract and therefore narrowing the blood vessels and the blood flow is slowed down. Furthermore the sympathetic nervous system is stimulated by baroreceptor upon which adrenaline and noradrenaline are released which increases the heart activity and as a result has an effect on the cardiac output.

It is also important that the mechanisms, which help decrease the blood pressure, are stimulated so the blood pressure is maintained at optimum level and avoid any disastrous consequences such as myocardial infarction, stroke, kidney related diseases and many other serious health problems.



The overall effect of all the essential mechanisms of regulating blood pressure on the body is to maintain normal blood pressure, which is around 120/80 mm Hg. If the blood pressure goes either above or below this value, the body is always ready to put all the essential mechanisms to regulate blood pressure.
Bibliography:

Widmaier, Eric. Vander’s Human Physiology. 11th edition. Michelle Watnick, 2007

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