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Also known as: '''''RAAS'''''

Also known as: '''''RAAS'''''

[[Image:raasflowsumap.jpg|right|thumb|250px|<small><center>Summary of the purpose of the RAAS</center></small>]]

[[Image:raasflowsumap.jpg|right|thumb|250px|<small><center>Summary of the purpose of the RAAS</center></small>]]

In the event of blood pressure dropping, [[Kidney Endocrine Function - Anatomy & Physiology#Renin|renin]] is secreted due to the decreased stretch of the [[Reabsorption and Secretion Along the Distal Tubule and Collecting Duct - Anatomy & Physiology#Juxtaglomerular Cells|'''juxtaglomerular cells''']] and an increased sympathetic stimulation, triggered by the decreased activation of arterial baroreceptors. This enzyme cleaves the alpha glycoprotein, '''angiotensinogen''', which is released from the [[Liver - Anatomy & Physiology|liver]]. This produces '''angiotensin 1''', which is further converted by [[Angiotensin Converting Enzyme|'''Angiotensin Converting Enzyme''' (ACE)]] to '''angiotensin II''', mainly in the lungs but to a much lesser extent locally in the kidneys. Angiotensin 2 then works to restore blood pressure by inducing constriction of arterioles, which increases vascular resistance, and constricting veins which reduces vascular volume. In this section, we cover its effects on and through the kidneys.

In the event of blood pressure dropping, [[Kidney Endocrine Function - Anatomy & Physiology#Renin|renin]] is secreted due to the decreased stretch of the [[Reabsorption and Secretion Along the Distal Tubule and Collecting Duct - Anatomy & Physiology#Juxtaglomerular Cells|'''juxtaglomerular cells''']] and an increased sympathetic stimulation, triggered by the decreased activation of arterial baroreceptors. This enzyme cleaves the alpha glycoprotein, '''angiotensinogen''', which is released from the [[Liver - Anatomy & Physiology|liver]]. This produces '''angiotensin 1''', which is further converted by [[Angiotensin Converting Enzyme|'''Angiotensin Converting Enzyme''' (ACE)]] to '''angiotensin II''', mainly in the lungs but to a much lesser extent locally in the kidneys. Angiotensin II then works to restore blood pressure by inducing constriction of peripheral vessels (arterioles), which increases vascular resistance, and constricting veins which reduces vascular volume. In this section, we cover its effects on and through the kidneys.

==Effects of Angiotensin II on Blood Pressure==

==Effects of Angiotensin II on Blood Pressure==

'''Angiotensin II''' acts on '''AT1 receptors''' to stimulate the release of '''[[Aldosterone|aldosterone]]''' from the [[Adrenal Glands - Anatomy & Physiology#Adrenal Glands|zona glomerulosa]] of the adrenal glands. This mineralocorticoid increases the reabsorption of sodium, and therefore water and chloride from the distal tubule of the kidney, thus helping to increase blood pressure and volume. It also stimulates the thirst center, and increases the secretion of [[Pituitary Gland - Anatomy & Physiology #Posterior Pituitary Gland |anti-diuretic hormone (ADH)]] to help increase blood volume. The RAAS allows pressure to return to 50% of baseline within 15 minutes of a significant haemorrhage occuring.

'''Angiotensin II''' acts on '''AT1 receptors''' to stimulate the release of '''[[Aldosterone|aldosterone]]''' from the [[Adrenal Glands - Anatomy & Physiology#Adrenal Glands|zona glomerulosa]] of the adrenal glands. This mineralocorticoid increases the excretion of potassium and the reabsorption of sodium, and therefore water and chloride from the distal tubule of the kidney, thus helping to increase blood pressure and volume. It also stimulates the thirst center, and increases the secretion of [[Pituitary Gland - Anatomy & Physiology #Posterior Pituitary Gland |anti-diuretic hormone (ADH)]] to help increase blood volume by making the distal convoluted tubule and the collecting duct permeable to water. The RAAS allows pressure to return to 50% of baseline within 15 minutes of a significant haemorrhage occurring.

==Effects of Angiotensin II on GFR==

==Effects of Angiotensin II on GFR==

If blood pressure drops then [[Glomerular Apparatus and Filtration - Anatomy & Physiology#Glomerular Filtration Rate|glomerular filtration rate (GFR)]] also drops, due to reduced blood flow through the kidneys. To restore homeostasis, contraction of the efferent arteriole occurs in response to angiotensin II and the pressure difference between the afferent and efferent arterioles increases, creating greater filtration pressure. When blood pressure falls therefore, there is minimum alteration of GFR. The increased renal resistance to blood flow and the maintained GFR has many advantageous effects.   

If blood pressure drops then [[Glomerular Apparatus and Filtration - Anatomy & Physiology#Glomerular Filtration Rate|glomerular filtration rate (GFR)]] also drops, due to reduced blood flow through the kidneys. To restore homeostasis, contraction of the efferent arteriole occurs in response to angiotensin II and the pressure difference between the afferent and efferent arterioles increases, creating greater filtration pressure. Therefore, when blood pressure falls, there is minimum alteration of GFR. The increased renal resistance to blood flow and the maintained GFR has many advantageous effects.   

===Advantages of Angiotensin II induced Vasoconstriction===

===Advantages of Angiotensin II induced Vasoconstriction===

Angiotensin II also stimulates the release of '''Aldosterone'''.

Angiotensin II also stimulates the release of '''Aldosterone'''.

==Links==

|flashcards = [[Important Hormonal Regulators of the Kidney - Renal Flash Cards - Anatomy & Physiology|Hormonal Regulators of the Kidney]]

Click here for the [[Important Hormonal Regulators of the Kidney - Renal Flash Cards - Anatomy & Physiology|Hormonal Regulators of the Kidney flashcards]]

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[[Category:Kidney Hormonal Regulators]][[Category:Endocrine System - Anatomy & Physiology]]

[[Category:Kidney Hormonal Regulators]][[Category:Endocrine System - Anatomy & Physiology]]

[[Category:Blood Pressure]]

[[Category:Blood Pressure]]

[[Category:To Do - AimeeHicks]]

[[Category:A&P Done]]

[[Category:Cardiology Section]]