The human heart pumps blood through the arteries, which connect to smaller arterioles and then smaller capillaries. In this assignment, we will discuss the arterial blood pressure from several aspects, include definition, normal values for blood pressure, the most important factors affecting it, the mechanism involved in arterial blood pressure regulation, and the relevance between the pressure and the eye.
Definition of blood pressure, it’s Normal value, and the factors that determine arterial blood pressure under physiologic conditions.
Blood pressure refers to the force exerted by the blood against the inner walls of the blood vessels . This pressure produces when the heart contracts during the heartbeat cycle, which forces blood out
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The Atrial reflex:
The atria have in their walls stretch receptors called low-pressure receptors
These low-pressure receptors play an important role, especially in minimizing arterial pressure changes in response to changes in blood volume.
They do detect simultaneous increases in pressure in the low-pressure areas of the circulation caused by an increase in volume, and elicit reflexes parallel to the baroreceptor reflexes to make the total reflex system more potent for control of arterial pressure.
b) Long term mechanism for control of blood pressure:
Is determined by the balance between the fluid intake and output.
1. The Renin-Angiotensin System
Renin is synthesized and stored in an inactive form called prorenin in the juxtaglomerular cells of the kidneys. These cells are modified smooth muscle cells located in the walls of the afferent arterioles. When the arterial pressure falls, intrinsic reactions in the kidneys themselves cause many of the prorenin molecules in the JG cells to split and release renin.
Most of the renin enters the renal blood and then passes out of the kidneys to circulate throughout the entire body .
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Way sodium excretion affects pressure can be described as follows: if the kidney requires high pressure to excrete a given load of salt, then, at lower pressures, sodium and water are retained, and the blood volume rises. An increased blood volume returns more blood to the heart, thereby increasing cardiac output. The increased output is sensed by the peripheral vessels, which do not like increased flow and constrict in response, and auto regulation increases arterial resistance. The reverse occurs when the pressure rises: more salt and water are excreted, and that lowers blood volume, which reduces cardiac output. Sensing lesser flow, arterioles auto regulates by dilating, which reduces peripheral resistance.
2. Too Much Vasoconstrictor Activity:
Postulated hypertension as the cause of essential hypertension. The list includes norepinephrine, angiotensin, aldosterone, thromboxane, and endothelin. More than a small proportion of hypertension, but that they all contribute in some circumstances to pressure regulation. Ironically, one-fourth to one third of all patients with essential hypertension have low plasma-renin activity that responds sluggishly to standard stimuli such as upright posture. Despite the low plasma-renin activity in low-renin essential hypertension, plasma aldosterone is