Anatomy And Physiology

Anatomy Physiology

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Potassium ions are alkali metal ions which are important physiologically due to their important function in nerve conduction and muscle contraction.  For this reason the body has allocated two known hormones to regulate their level in the blood.  This is in addition to regulation which is performed as ion pumps. 

Potassium ions are very important in performing normal heart function.  It does this by maintaining an electrical potential across the cellular membrane of muscle cells.  It does this also with the help of ion pumps which conjugate the transport of potassium ions from the outside of the cell to its interior side with the concomitant transport of sodium in the opposite direction. 

For all these reasons any minimal change in potassium ions whether it is hyperkalemia or hypokalemia can affect the function of the nervous system and heart function as well.  The first hormone that is discussed here and which regulates the concentration of potassium ions in the extracellular space is insulin.

Insulin in addition to its known function on glucose transport into the cell also functions by stimulating the entry of potassium ions into the cells.  This function is especially manifested in diabetes mellitus in which insulin is absent in the blood or is low in concentration.  In this case a hyperkalemic state  occurs which is caused by the accumulation of potassium ions in the extracellular space. 

Injection of insulin in these patients can correct the hyperkalemia to its normal value.  Also in diabetes mellitus in which a hyperglycemic state is present the glucose in the extracellular space exerts an osmotic effect thus withdrawing water outside the cell.  This concentrates potassium in the cell which leads to its move outside the cell.  Thus causing a state of hyperkalemia also.

The second important hormone which also functions by regulating potassium level in the blood indirectly is the steroid hormone aldosterone.  Aldosterone is a hormone which clinically its excess can cause hypertension and edema.  It usually functions by conserving sodium ions that are filtered in the kidney glomeruli into the circulation. 

An ion pump that exchanges sodium for potassium excrete potassium in the urine in exchange for sodium which is conserved by the effect of aldosterone.  This is a normal process which guarantees an appropriate concentration of sodium and potassium ions in the blood. 

Pathology that involves aldosterone whether it is hyperaldosteronism or hypoaldosteronism can be manifested as abnormal concentration of sodium as well as potassium ions in the blood.  In the case of hyposecretion of aldosterone a condition which is called Addison's disease there is a state of hyperkalemia due to the wasting of sodium ions in the urine which results due to the lack of sodium reabsorption in the kidney tubules. 

In the case of hypersecretion of aldosterone a condition which is called Conn's syndrome a state of hypokalemia occurs due to the excessive conservation of sodium into the blood in exchange for potassium which is secreted in the urine.  In pathologic states such as muscle injury a state of hyperkalemia can occur due to the leakage of potassium ions from the injured cells into the extracellular space. 

The same condition of hypekalemia can occur also in hemolytic anemia in which red blood cells destruction leads to the leakage of hemoglobin as well as potassium ions as well as all other cellular constituents. 

Activation of the sympathetic nervous system can stimulates a state of hypokalemia by increasing the uptake of potassium by the cells of the body.  Acidosis of the blood causes a state of hyperkalemia due to the activation of K+ / H+ cellular ion pump in which acid is inserted into the cell to be buffered and neutralized inside the cell in exchange for potassium which is exited from the cell to the outside of the cell.  Thus causing hyperkalemia.

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