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Monthly Archives: June 2016

Regulation of Sodium Excretion


Percentage of Sodium Reabsorbed The Goals of Regulation The overriding goals of regulating sodium and water excretion are to support the requirements of the cardiovascular system. This is manifested in 3 ways: 1.the kidneys maintain a sufficient ECF volume to fill the vascular space (mean circulatory filling pressure); 2.keep the osmolality of the ECF at a level […]

Control of the Circulating RAAS


The activity of the circulating RAAS is governed by the amount of renin secreted by the granular cells of the jg (juxtaglomerular) apparatus. There are 3 major controllers of renin secretion. PS: Look at the RAAS, plasma angiotensinogen is synthesized in the liver and plasma angiotensinogen levels are normally high therefore do not limit the production […]

Urinary Concentration – The Medullary Osmotic Gradient


The kidneys can produce a range of urine osmolalities depending on the levels of ADH. The production of hypo-osmotic urine is an understandable process: The tubules (particularly the thick ascending limb of Henle's loop) reabsorb relatively more solute than water, and the dilute fluid that remains in the lumen is excreted. The production of hyperosmotic […]

Effect of Respiratory Activity on Circulation


The physical processes associated with inhaling air into and exhaling air out of the lungs can have major effects on venous return and cardiac output. During a normal inspiration, intrathoracic pressure falls from approximately negative 2 mm Hg to approximately negative 7 mm Hg as the diaphragm contracts and the chest wall expands. It rises […]

[Physiology] Regulation of Arterial Pressure


Appropriate systemic arterial pressure is the single most important requirement for proper operation of the cardiovascular system. Without sufficient arterial pressure, the brain and the heart do not receive adequate blood flow, no matter what adjustments are made in their vascular resistance by local control mechanisms. In contrast, unnecessary demands are placed on the heart […]