Glomerular Filtration Rate - Revision history

Fiorecastro at 17:48, 4 January 2023

2023-01-04T17:48:08Z

Bara at 11:36, 3 July 2012

2012-07-03T11:36:10Z

Bara at 11:15, 28 April 2011

2011-04-28T11:15:18Z

Bara at 16:33, 10 December 2010

2010-12-10T16:33:57Z

Bara at 16:22, 10 December 2010

2010-12-10T16:22:43Z

Bara: Text replace - "[[Kidney - Blood Pressure - Anatomy & Physiology" to "[[Kidney Control of Blood Pressure - Anatomy & Physiology"

2010-12-10T14:29:31Z

Text replace - "[[Kidney - Blood Pressure - Anatomy & Physiology" to "[[Kidney Control of Blood Pressure - Anatomy & Physiology"

Bara at 18:04, 9 December 2010

2010-12-09T18:04:25Z

Bara at 18:03, 9 December 2010

2010-12-09T18:03:27Z

Bara at 18:01, 9 December 2010

2010-12-09T18:01:42Z

Bara at 17:59, 9 December 2010

2010-12-09T17:59:36Z

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-{{OpenPagesTop}}
 ==Introduction==
 The glomerular filtration rate or GFR is the amount of fluid filtered from the capillaries into the Bowmans capsule of the kidneys per unit time.  The GFR can be expressed as the following formula:
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-{{OpenPages}}
+==Webinars==
 [[Category:Urine Production]]

@@ Line 1: / Line 1: @@
 ==Introduction==
 The glomerular filtration rate or GFR is the amount of fluid filtered from the capillaries into the Bowmans capsule of the kidneys per unit time.  The GFR can be expressed as the following formula:
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+{{OpenPages}}
 [[Category:Urine Production]]

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 ==Introduction==
-The glomerular filtration rate or GFR is the amount of fluid filtered from the capillaries into the Bowmans capsule per unit time.  The GFR can be expressed as the following formula:
+The glomerular filtration rate or GFR is the amount of fluid filtered from the capillaries into the Bowmans capsule of the kidneys per unit time.  The GFR can be expressed as the following formula:
 <center><big>'''GFR = K<sub>f</sub> x net filtration pressure'''</big></center>

← Older revision		Revision as of 16:33, 10 December 2010
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−	[[Category:~~Nephron~~]]	+	[[Category:Urine Production]]

← Older revision		Revision as of 16:22, 10 December 2010
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−	[[Category:~~Urinary System - Anatomy & Physiology~~]]	+	[[Category:Nephron]]

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 '''The Limitations of Autoregulation'''
-Despite the efforts of the autoregulatory system an increase in blood pressure still leads to an increased secretion of salt and water.  This is because even a small percentage change in GFR leads to large percentage change in the excretion of salt and water.  This excretion is however far less drastic than would be the case without autoregulation and actually helps to restore pressure to normal.  This increase in urinary output as a result of an increase in arterial blood pressure is termed [[Kidney - Blood Pressure - Anatomy & Physiology#Pressure Diuresis|pressure diuresis]].
+Despite the efforts of the autoregulatory system an increase in blood pressure still leads to an increased secretion of salt and water.  This is because even a small percentage change in GFR leads to large percentage change in the excretion of salt and water.  This excretion is however far less drastic than would be the case without autoregulation and actually helps to restore pressure to normal.  This increase in urinary output as a result of an increase in arterial blood pressure is termed [[Kidney Control of Blood Pressure - Anatomy & Physiology#Pressure Diuresis|pressure diuresis]].
 ===[[Renin Angiotensin Aldosterone System|Angiotensin 2]]===

@@ Line 33: / Line 33: @@
 Overall the constriction of the afferent arteriole decreases both blood flow and filtration pressure where as constricting the efferent arteriole decreases blood flow but increases filtration pressure.  (Both of these statements are assuming a constant blood pressure). The fact that both can be altered allows independent regulation of both GFR and blood flow.
-===Physiological Regulators of GFR===
+==Physiological Regulators of GFR==
 The main systems which regulate renal blood flow and GFR are:
-====Autoregulation====
+===Autoregulation===
 <center><big>'''Q = (PA - PE) &#247; R'''</big></center>
@@ Line 65: / Line 65: @@
 Despite the efforts of the autoregulatory system an increase in blood pressure still leads to an increased secretion of salt and water.  This is because even a small percentage change in GFR leads to large percentage change in the excretion of salt and water.  This excretion is however far less drastic than would be the case without autoregulation and actually helps to restore pressure to normal.  This increase in urinary output as a result of an increase in arterial blood pressure is termed [[Kidney - Blood Pressure - Anatomy & Physiology#Pressure Diuresis|pressure diuresis]].
-====[[Renin Angiotensin Aldosterone System|Angiotensin 2]]====
+===[[Renin Angiotensin Aldosterone System|Angiotensin 2]]===
-====Sympathetic Nervous System====
+===Sympathetic Nervous System===
 When the animal is in a situation of crisis or stress blood flow to the kidneys is reduced for the sake of other organs such as the brain, heart and skeletal muscles.  The sympathetic nervous system and a heightened level of adrenalin in the plasma cause the contraction of both the afferant and efferant arterioles.  As the efferant arteriole is contracted alongside the afferant one there is still a pressure differance allowing for filtration to still occur and reducing the impact on filtration compared to the impact on blood flow. At times when sympathetic tone is very high the renal blood flow could be reduced to 10-30% of normal.  This practically stops filtration occuring and thus stops urine production.
@@ Line 84: / Line 84: @@
 * Increased conservation of water and sodium
-====Nitrous Oxide and Prostaglandins====
+===Nitrous Oxide and Prostaglandins===
 Nitrous Oxide and Prostaglandins have an impact on arteriolar resistance. Their role in the regulation of renal blood flow and filtration is however uncertain.
-=====Nitrous Oxide=====
+====Nitrous Oxide====
 * Mediates dilation in the cortical circulation
-=====Prostaglandins=====
+====Prostaglandins====
 * Mediates dilation in medullary circulation (cortical in extremes)
 * PGE2 is involved in the regulation of the reabsorption of sodium
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 * In healthy/hydrated individuals these compounds do not play a significant role in sodium/water homeostasis
-=====Effects of Blocking Nitric Oxide or Prostaglandins=====
+====Effects of Blocking Nitric Oxide or Prostaglandins====
 * Loss of medullary circulation - reduced ability to concentrate water
 * Loss of medullary flow - reduces the ability to preserve sodium balance and maintain normal blood pressure

@@ Line 69: / Line 69: @@
 ====[[Renin Angiotensin Aldosterone System|Angiotensin 2]]====
-====[[Sympathetic Nervous System effect on Glomerular Filtration Rate|Sympathetic Nervous System]]====
+====Sympathetic Nervous System====
 ====[[The Effects of Nitrous Oxide and Prostaglandins on GFR - Anatomy & Physiology|Nitrous Oxide and Prostaglandins]]====
 [[Category:Urinary System - Anatomy & Physiology]]

@@ Line 17: / Line 17: @@
 <center><big>'''Q = (PA - PE) &#247; R'''</big></center>
 '''Q''' = Flow, '''PA''' = Pressure in afferent arteriole, '''PE''' = Pressure in efferent arteriole, '''R''' = Resistance
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 There are two major forces opposing GFR.  These are the hydrostatic pressure in the Bowmans space and the plasma protein osmotic pressure.  These are not under physiological control. The filtration coefficient is also beyond the realms of physiological control.  On the other hand the hydrostatic pressure in the capillaries and the renal blood flow are under physiological regulation and adjust filtration according to the bodies needs.
-===Regulation of Renal Blood Flow and Capillary Hydrostatic Pressure===
+==Regulation of Renal Blood Flow and Capillary Hydrostatic Pressure==
 These two factors are determined by the arterial blood pressure coupled with the contraction of both the afferent and efferent arterioles.  The total resistance of the afferent and efferent arterioles, which is determined by the contraction of them, determines the renal blood flow and any particular arterial pressure.  Therefore it is important that they change with arterial pressure in order to maintain a steady renal blood flow.
-====Constriction of the Afferent and Efferent Arterioles====
+===Constriction of the Afferent and Efferent Arterioles===
 Normally the afferent arteriole is of larger diameter than the efferent.  This means there is high resistance as the blood is forced from a wider vessel to a narrower one and this promotes filtration.  If the arterial blood pressure remains constant then contracting either vessel reduces blood flow as it increases resistance.  However contracting either has opposite effects on the filtration pressure.  If you contract the afferent arteriole there will be less of a pressure difference between the afferent and efferent arteriole so there will be reduced filtration pressure.  However if you constrict the efferent arteriole you are increasing the pressure difference between the two and filtration pressure increase.
@@ Line 32: / Line 33: @@
 Overall the constriction of the afferent arteriole decreases both blood flow and filtration pressure where as constricting the efferent arteriole decreases blood flow but increases filtration pressure.  (Both of these statements are assuming a constant blood pressure). The fact that both can be altered allows independent regulation of both GFR and blood flow.
-====Physiological Regulators of GFR====
+===Physiological Regulators of GFR===
 The main systems which regulate renal blood flow and GFR are:
-'''[[Autoregulation of GFR - Anatomy and Physiology|Autoregulation]]'''
+====Autoregulation====
-'''[[Renin Angiotensin Aldosterone System|Angiotensin 2]]'''
+====[[Renin Angiotensin Aldosterone System|Angiotensin 2]]====
-'''[[Sympathetic Nervous System effect on Glomerular Filtration Rate|Sympathetic Nervous System]].'''
+====[[Sympathetic Nervous System effect on Glomerular Filtration Rate|Sympathetic Nervous System]]====
-'''[[The Effects of Nitrous Oxide and Prostaglandins on GFR - Anatomy & Physiology|Nitrous Oxide and Prostaglandins]]'''
+====[[The Effects of Nitrous Oxide and Prostaglandins on GFR - Anatomy & Physiology|Nitrous Oxide and Prostaglandins]]====
 [[Category:Urinary System - Anatomy & Physiology]]