Changes

*reduced concentration of potassium in the ECF leads to plasma membranes hyperpolarization resulting in decreased firing of action potentials.  This causes skeletal muscle weakness and cardiac abnormalities.

*reduced concentration of potassium in the ECF leads to plasma membranes hyperpolarization resulting in decreased firing of action potentials.  This causes skeletal muscle weakness and cardiac abnormalities.

*increased concentration of potassium in the ECF leads to membrane depolarisation which is inappropriately triggered by action potentials.  This can make the membrane insensitive to further stimulation causing cardiac abnormalities.

*increased concentration of potassium in the ECF leads to membrane depolarisation which is inappropriately triggered by action potentials.  This can make the membrane insensitive to further stimulation causing cardiac abnormalities.

==Sources of Potassium==

==Sources of Potassium==

Potassium is absorbed via passive diffusion from the [[Small Intestine Overview - Anatomy & Physiology|small intestine]] and via active transport from the [[Colon - Anatomy & Physiology|colon]]. It is regulated efficiently by [[Aldosterone|aldosterone]] levels and recovery from cellular breakdown during haemolysis or tissue damage.

Potassium is absorbed via passive diffusion from the [[Small Intestine Overview - Anatomy & Physiology|small intestine]] and via active transport from the [[Colon - Anatomy & Physiology|colon]]. It is regulated efficiently by [[Aldosterone|aldosterone]] levels and recovery from cellular breakdown during haemolysis or tissue damage.

The K⁺ in the ECF only represents a very small amount of the total K⁺ in the body; however its concentration is maintained within very strict parameters.  The homeostasis of K⁺ is managed by three routes:

The K⁺ in the ECF only represents a very small amount of the total K⁺ in the body; however its concentration is maintained within very strict parameters.  The homeostasis of K⁺ is managed by three routes:

#Cellular translocation - this is the main method of control; it is an acute response that triggers Potassium movement either into or out of the cells.  

#Cellular translocation - this is the main method of control; it is an acute response that triggers Potassium movement either into or out of the cells.  

#Renal excretion - this method makes up 90% of the chronic response (takes 4-6 hours to respond). It allows fine control and is regulated by [[Aldosterone|Aldosterone]]

#Renal excretion - this method makes up 90% of the chronic response (takes 4-6 hours to respond). It allows fine control and is regulated by [[Aldosterone|aldosterone]]

#GI excretion - this route makes up the other 10% of the chronic response and becomes significant in cases of renal failure. This response is also influenced by [[Aldosterone]].

#GI excretion - this route makes up the other 10% of the chronic response and becomes significant in cases of renal failure. This response is also influenced by [[Aldosterone|aldosterone]]

==Cellular Translocation==

==Cellular Translocation==

* 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

==Factors Influencing Potassium Excretion==

==Factors Influencing Potassium Excretion==

#Sodium: High sodium = increased potassium excretion and:

1.Sodium: High sodium = increased potassium excretion and:

* More sodium into cells  

* More sodium into cells  

* Increased Na⁺ / K⁺ ATPase

* Increased Na⁺ / K⁺ ATPase

* The resulting increased cellular uptake of potassium results in it moving down the electrochemical gradient into the nephron

* The resulting increased cellular uptake of potassium results in it moving down the electrochemical gradient into the nephron

2.Potassium: High potassium = increased potassium excretion which triggers the release of aldosterone.

2.Potassium: High potassium = increased potassium excretion which triggers the release of aldosterone.

[[Category:Electrolytes]]

[[Category:Electrolytes]]