Systems regulating blood pressure globally Renin-angiotensin-aldosterone system: When the kidney juxtaglomerular cells detect a decrease in blood flow secrete renin, which converts angiotensinogen into angiotensin I which is converted to angiotensin II by ACE (enzyme angiotensin converting), angiotensin II is a potent vasoconstrictor also promotes the secretion of aldosterone, which reduces water loss through urine. It also acts on subfornical organ to induce thirst. Vasopressin: When hippocampal cells detected an increase in cerebrospinal fluid osmolarity secrete vasopressin (also known as antidiuretic hormone or ADH) that promotes water reabsorption by the kidney and in turn a potent vasoconstrictor, this system is responsible that salt increases blood pressure, because it increases the osmolarity of cerebrospinal fluid.Adrenaline-Noradrenaline: In stressful situations kidney adrenal glands secrete two hormones that alter the rate and force of contraction of the heart, in addition to causing vasodilation or vaso-constriction according to areas of the capillary network neural factors: in cases of stress or threat activates the sympathetic nervous system increases heart rate by a decrease in potassium permeability and an increase in calcium from the cardiac pacemaker cells. This allows the voltage threshold for generating an action potential can be achieved before (in cardiac pacemaker cells constantly sodium comes when the membrane reaches a threshold potential leads to opening of calcium channels, which leads to increased flow depolarization, allowing faster excitement the rest of the heart tissue and subsequent contraction. This electrical movement is what is observed on the electrocardiogram).However, stress reduction causes a parasympathetic activation, resulting in a decrease in calcium permeability, increase in potassium and consequent decrease in heart rate.