Changes

* Takes 4-6 hours to respond

* Takes 4-6 hours to respond

* Allows fine control

* Allows fine control

* Influenced by [[Aldosterone|Aldosterone]]

* Influenced by [[Aldosterone|aldosterone]]

=====GI excretion=====

=====GI excretion=====

* Makes up the other 10% of the chronic response

* Makes up the other 10% of the chronic response

* Also influenced by [[Aldosterone]]

* Also influenced by [[Aldosterone|aldosterone]]

* Most important in renal failure

* Most important in renal failure

* However net reabsorption / secretion of potassium occurs in the distal tubule and first part of collecting duct

* However net reabsorption / secretion of potassium occurs in the distal tubule and first part of collecting duct

** Depends on bodies need

** Depends on bodies need

* Under the influence of [[Aldosterone]]

* Under the influence of [[Aldosterone|aldosterone]]

* This is where the amount of potassium excreted is determined

* This is where the amount of potassium excreted is determined

* Reabsorption occurs in the final part of the collecting duct

* Reabsorption occurs in the final part of the collecting duct

* [[Aldosterone]] is the most important regulator of potassium

* [[Aldosterone]] is the most important regulator of potassium

* It causes increased secretion of potassium

* It causes increased secretion of potassium

* Increased potassium directly stimulates [[Aldosterone]] secretion

* Increased potassium directly stimulates [[Aldosterone|aldosterone]] secretion

* Increases the activity and number of Na⁺ / K⁺ ATPase in basolateral membranes of the principal cells in the collecting duct and distal tubule

* Increases the activity and number of Na⁺ / K⁺ ATPase in basolateral membranes of the principal cells in the collecting duct and distal tubule

* Potassium moves into the cells and is then excreted down an electro-chemical gradient

* Potassium moves into the cells and is then excreted down an electro-chemical gradient

==Acid / Base==

==Acid / Base==

It is essential that 50-100meq of acid is excreted by the kidneys every day.  This is achieved by secretion of H⁺ in two regions of the nephron, the proximal tubule and the collecting ducts, and is essential for maintaining the acid base ratio, within the body, at the correct levels. If there is a net gain or loss of H⁺ within the body then the kidneys will compensate for it.  The H⁺ ions cannot be secreted as free ions, however virtually all filtered HCO₃^- must be reabsorbed.  The result is that the H⁺ ions bind to other filtered buffers which are not fully reabsorbed such as ammonia or phosphate.  Extracellular pH is th main physiological regulator affecting how much acid is secreted.  In pathological states circulating volume, aldosterone and plasma potassium affect it.

It is essential that 50-100meq of acid is excreted by the kidneys every day.  This is achieved by secretion of H⁺ in two regions of the nephron, the proximal tubule and the collecting ducts, and is essential for maintaining the acid base ratio, within the body, at the correct levels. If there is a net gain or loss of H⁺ within the body then the kidneys will compensate for it.  The H⁺ ions cannot be secreted as free ions, however virtually all filtered HCO₃^- must be reabsorbed.  The result is that the H⁺ ions bind to other filtered buffers which are not fully reabsorbed such as ammonia or phosphate.  Extracellular pH is the main physiological regulator affecting how much acid is secreted.  In pathological states circulating volume, aldosterone and plasma potassium affect it.

===The Role of the Kidneys in Acid Base===

===The Role of the Kidneys in Acid Base===

=====Alkalosis=====

=====Alkalosis=====

In a situation of alkalosis the kidneys allow more HCO₃^- to be excreted.  This results in an increase in an increase of un-buffered H⁺ and thus returns the pH towards normal.

In a situation of alkalosis the kidneys allow more HCO₃^- to be excreted.  This results in an increase of un-buffered H⁺ and thus returns the pH towards normal.

=====Acidosis=====

=====Acidosis=====

==Calcium==

==Calcium==

[[Calcium Homeostasis - Anatomy & Physiology|Calcium Homeostasis]] has three aspects:

[[Calcium|Calcium Homeostasis]] has three aspects:

* Renal reabsorption - dealt with here

* Renal reabsorption - dealt with here

* Intestinal absorption

* Intestinal absorption

* [[Calcium Homeostasis - Anatomy & Physiology| Exchange processes from the bones]]

* [[Calcium| Exchange processes from the bones]]

==Urea==

==Urea==

[[Category:Urinary System]]

[[Category:Nephron]]

[[Category:Bullet Points]]