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−Potassium is generally in the range of 2 to 8 mmol/l. Hypokalaemia in reptiles will occur from inadequate intake or excessive loss (diarrhoea). In mammals hyperkalaemia with excessive potassium intake, decresed secretion or shift from intracellular to extracellular fluid (e.g.severe acidosis).
−====Decreased Extracellular Potassium====+ +If the concentration of potassium in the ECF is reduced then the plasma membranes hyperpolarize resulting in decreased firing of action potentials. This causes skeletal muscle weakness and cardiac abnormalities.+ +====Increased Extracellular Potassium====+ +In this state the membrane is depolarised and is inappropriately triggered by action potentials. This can make the membrane insensitive to further stimulation causing cardiac abnormalities.+ +===Sources===
−
−* Potassium is absorbed via passive diffusion from the [[Small Intestine Overview - Anatomy & Physiology|small intestine]]
−* Also via active transport from the [[Colon - Anatomy & Physiology|colon]]
−** Affected by [[Aldosterone]]
−* Highly efficient
−* It's recovered from cellular breakdown
−** Haemolysis
−** Tissue damage
−
−===Methods of Control===
−
−=====Cellular translocation=====
−*Potassium is moved either into or out of the cells
−*Acute response
−* Main method of control
−
−=====Renal excretion=====
−* Makes up 90% of the chronic response
−* Takes 4-6 hours to respond
−* Allows fine control
−* Influenced by [[Aldosterone|Aldosterone]]
−
−=====GI excretion=====
−* Makes up the other 10% of the chronic response
−* Also influenced by [[Aldosterone]]
−* Most important in renal failure
−
−===Cellular Translocation===
+===Renal Control===+===Potassium and Aldosterone===+
===Factors Influencing Potassium Excretion===+====Sodium====+ +* High sodium = increased potassium excretion+** More sodium into cells +** Increased Na<sup>+</sup> / K<sup>+</sup> ATPase+** Pumps sodium into peritubular renal interstitium+** The resulting increased cellular uptake of potassium results in it moving down the electrochemical gradient into the nephron
−
−====Potassium====
−
−* High potassium = increased potassium excretion
−* Triggers aldosterone
==Potassium==
+==Introduction==
+Potassium is carefully regulated in the body - the consequences of altered Potassium levels are significant, including:
+*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.
−===Importance of Regulation===
+==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]] levels and recovery from cellular breakdown during haemolysis or tissue damage.
−==Methods of Control==
−The K<sup>+</sup> in the ECF only represents a very small amount of the total K<sup>+</sup> in the body; however its concentration is maintained within very strict parameters. The homeostasis of K<sup>+</sup> 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.
−#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]].
−The K<sup>+</sup> in the ECF only represents a very small amount of the total K<sup>+</sup> in the body however its concentration is maintained within very strict parameters. The homeostasis of K<sup>+</sup> is managed by three routes:
−==Cellular Translocation==
* Vital for rapid control of potassium loads
* Vital for rapid control of potassium loads
* Helps control plasma concentration
* Helps control plasma concentration
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** Increases the activity of Na<sup>+</sup> / K<sup>+</sup> ATPases causing sodium efflux and potassium influx
** Increases the activity of Na<sup>+</sup> / K<sup>+</sup> ATPases causing sodium efflux and potassium influx
−==Renal Control==
* Potassium ions are reabsorbed and secreted at different points along the nephron
* Potassium ions are reabsorbed and secreted at different points along the nephron
* Active reabsorption of potassium occurs along the [[Reabsorption and Secretion Along the Proximal Tubule - Anatomy & Physiology|proximal tubule]] (70%) and along the ascending limb of the [[Reabsorption and Secretion Along the Loop of Henle - Anatomy & Physiology| Loop of Henle]] (10-20%)
* Active reabsorption of potassium occurs along the [[Reabsorption and Secretion Along the Proximal Tubule - Anatomy & Physiology|proximal tubule]] (70%) and along the ascending limb of the [[Reabsorption and Secretion Along the Loop of Henle - Anatomy & Physiology| Loop of Henle]] (10-20%)
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* Reabsorption occurs in the final part of the collecting duct
* Reabsorption occurs in the final part of the collecting duct
−==Potassium and Aldosterone==
−* [[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
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* 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
−==Factors Influencing Potassium Excretion==
−#Sodium: High sodium = increased potassium excretion and:
−* More sodium into cells
−* Increased Na<sup>+</sup> / K<sup>+</sup> ATPase
−* Pumps sodium into peritubular renal interstitium
−* The resulting increased cellular uptake of potassium results in it moving down the electrochemical gradient into the nephron
−#Potassium: High potassium = increased potassium excretion which triggers the release of aldosterone.
−[[Category:Electrolytes]]
[[Category:Electrolytes]]
[[Category:Lizard_and_Snake_Glossary]]
[[Category:Lizard_and_Snake_Glossary]]
[[Potassium - Reptiles]]
[[Potassium - Reptiles]]