Changes

==Effects of Angiotensin II on GFR==

==Effects of Angiotensin II on GFR==

If blood pressure drops then [[The Formation of the Filtrate by the Glomerular Apparatus- 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. 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.   

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

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

* Increased total peripheral resistance helps to return blood pressure towards normal.  (Angiotensin II also has vasoconstrictive effects in multiple organs.)

* Increased total peripheral resistance helps to return blood pressure towards normal.  (Angiotensin II also has vasoconstrictive effects in multiple organs.)

* The reduced perfusion of the kidneys allows blood to be diverted to the brain and heart.

* The reduced perfusion of the kidneys allows blood to be diverted to the brain and heart.

* The constriction of the efferent arterioles also reduces hydrostatic pressure in the [[The Formation of the Filtrate by the Glomerular Apparatus- Anatomy & Physiology#Pressure in the Peritubular Capillaries|peritubular capillaries]], increasing reabsorption of water and salt and helping to restore the extracellular fluid ECF and normalising blood pressure.

* The constriction of the efferent arterioles also reduces hydrostatic pressure in the [[Glomerular Apparatus and Filtration - Anatomy & Physiology#Pressure in the Peritubular Capillaries|peritubular capillaries]], increasing reabsorption of water and salt and helping to restore the extracellular fluid ECF and normalising blood pressure.

* The amount of waste excreted is linked to the GFR.  Maintaining GFR permits the excretion of waste products such as urea to be maintained.

* The amount of waste excreted is linked to the GFR.  Maintaining GFR permits the excretion of waste products such as urea to be maintained.