help!??!? + BIO~?!?

Question

Can someone describe to me the mechanism by which aldosterone helps maintain blood pressure. But when you explain it to me can you start with the low blood pressure.

Answer 1

The renin-angiotensin system (RAS) or the renin-angiotensin-aldosterone system (RAAS) is a hormone system that helps regulate long-term blood pressure and extracellular volume in the body.

The system can be activated when there is a loss of blood volume or a drop in blood pressure (such as in a hemorrhage).

If the perfusion of the juxtaglomerular apparatus in the kidneys decreases, then the juxtaglomerular cells release the enzyme renin.

Renin cleaves an inactive peptide called angiotensinogen, converting it into angiotensin I.

Angiotensin I is then converted to angiotensin II by angiotensin-converting enzyme (ACE)

Answer 2

Aldosterone is a steroid hormone (mineralocorticoid family) produced by the outer-section (zona glomerulosa) of the adrenal cortex in the adrenal gland to regulate sodium and potassium balance in the blood.

Control of aldosterone release in the kidney the role of the renin-angiotensin system or renin-angiotensin-aldosterone system (RAAS) which is a hormone system that helps regulate long-term blood pressure and extracellular volume in the body.

The system can be activated when there is a loss of blood volume or a drop in blood pressure.

If the perfusion of the juxtaglomerular apparatus in the kidneys decreases, then the juxtaglomerular cells release the enzyme renin.

Renin cleaves an inactive peptide called angiotensinogen, converting it into angiotensin I.

Angiotensin I is then converted to angiotensin II by angiotensin-converting enzyme (ACE),which is found mainly in lung capillaries.

Angiotensin II has a variety of effects on the body:

Throughout the body, it is a potent vasoconstrictor(that acts to cause vasoconstriction (narrowing of the lumena of blood vessels) and usually results in an increase of the blood pressure.

In the kidneys, it constricts glomerular arterioles, having a greater effect on efferent arterioles than afferent,the constriction of afferent arterioles increases the arterioler resistance, raising systemic arterial blood pressure and decreasing the blood flow. However, the kidneys must continue to filter enough blood despite this drop in blood flow, necessitating mechanisms to keep glomerular blood pressure up. To do this, Angiotensin II constricts efferent arterioles, which forces blood to buildup in the glomerulus, increasing glomerular pressure. The glomerular filtration rate (GFR) is thus maintained, and blood filtration can continue despite lowered overall kidney blood flow.

Answer 3

All those long answers, and no one said what aldosterone actually *does*.

Aldosterone increases tubular reabsorption of sodium. Simply put, it stops you from urinating out your sodium. By osmosis, your body will also retain water with that sodium. Increased volume of liquid in your blood vessels = increased blood pressure.

How does your body know when to increase secretion of aldosterone? There are multiple ways in which your body regulates aldosterone secretion; but, with regards to blood pressure, the renin-angiotensin system is the most important.

Low blood pressure causes increased renin secretion by a few different mechanisms. There are internal baroreceptors in the juxtaglomerular apparatus that secrete renin in response to low pressure in the afferent arterioles. When flow in the macula densa decreases (as detected by decreased sodium and chloride concentrations in the macula densa lumen), renin secretion is stimulated. Low blood pressure detected by extrarenal baroreceptors can also stimulate renin secretion via sympathetic neurons that end in the vicinity of the juxtaglomerular apparatus.

Renin is a proteolytic enzyme that cleaves angiotensinogen into angiotensin I. Angiotensinogen is a pro-enzyme that is continually produced mainly by the liver and circulates in the bloodstream. Angiotensin I is converted to angiotensin II by angiotensin-converting enzyme (ACE) which is present all over the vascular endothelium, and in particularly large amounts in the pulmonary capillaries in the lung.

Angiotensin II directly increases blood pressure by causing vasoconstriction, but this question was about aldosterone, right? Angiotensin II also stimulates aldosterone secretion. This is the primary method by which aldosterone secretion is tied to low blood pressure.