seizures

[ctizzle13498]

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in dit's workbook, it says that ADH causes hyponatremic seizures.

I thought that seizures were rapid neural excitement, so wouldn't hypernatremia cause seizures and not hyponatremia?

 

[jfgavina]

I think hyponatremia can cause seizures via the cerebral edema mechanism, so your neurons are compressed and for some reason you decrease your seizure threshold and seizures ensue..

 

[OveractiveBrain]

I think hyponatremia can cause seizures via the cerebral edema mechanism, so your neurons are compressed and for some reason you decrease your seizure threshold and seizures ensue..

Yep...

If your are hypernatremic (means hyperosmolar blood) you suck water out of cells, and they shrivel and die. Bad for cells.

If you are hyponatremic (means hypoosmolar blood) water rushes into the cells, and they swell, or pop. bad for cells.

"Bad for cells" in the brain mean either unnecessary exictatory neuronal firing or supressed inhibitory neuronal firing. Leads to seizures.

Both Hyponatremia and Hypernatremia can lead to seizures. Especially when the change is fast or really big. Disorders of sodium are actually disorders of water.

 

[rashy]

Since we are talking about sodium... Can someone PLEASE explain to me WHY our Body Water is regulated by sodium? E.g. let's take Aldosterone. Its action is to exchange Sodium for Potassium in the tubules. One ion for another. So WHY is there a net absorption of water into the body ?!?! That's something that has been bothering me for a while now and noone seems to know!

 

[jfgavina]

There are 2 ways that increase water in your body (there may be others but these are the 2 most important and account for net changes): aldosterone and ADH. ADH I think you understand, your problem is with aldosterone and I'll make it simple: if you absorb Na water always follows! It is a osmolarity matter. to keep the osmolarity water must follow Na, because Na determines the osmolarity!! Only if you have high concentrations of glucose, lets say about 700 or 800 glucose becomes the major ruler of osmolarity, and this is hyperosmolar coma!!

and you may be thinking, well Na Cl and K are all absorbed in the thick ascensing limb of the loop of henle and water doesn't follow, well that's because that segment of the kidney isn't permeable to water!!

 

[rashy]

There are 2 ways that increase water in your body (there may be others but these are the 2 most important and account for net changes): aldosterone and ADH. ADH I think you understand, your problem is with aldosterone and I'll make it simple: if you absorb Na water always follows! It is a osmolarity matter. to keep the osmolarity water must follow Na, because Na determines the osmolarity!! Only if you have high concentrations of glucose, lets say about 700 or 800 glucose becomes the major ruler of osmolarity, and this is hyperosmolar coma!!

and you may be thinking, well Na Cl and K are all absorbed in the thick ascensing limb of the loop of henle and water doesn't follow, well that's because that segment of the kidney isn't permeable to water!!

Actually, I bet you just learned this "Water always follows Na" by heart because everybody is saying it! 😉 But osmolarity is not just determined by Na, it is determined by every ion. And if you exchange an Na for a K, why should there be any waterflow?? There is a 1:1 exchange in ions. The osmolarity stays the same on both sides. So why the water flow?

 

[123165]

Actually, I bet you just learned this "Water always follows Na" by heart because everybody is saying it! 😉 But osmolarity is not just determined by Na, it is determined by every ion. And if you exchange an Na for a K, why should there be any waterflow?? There is a 1:1 exchange in ions. The osmolarity stays the same on both sides. So why the water flow?

3 sodium out of the tubule cell, 2 potassium in

net reabsorption of Na

 

[jfgavina]

no, no I think that pump is not used in the kidney! Na determines osmolarity, goljan says

 

[123165]

no, no I think that pump is not used in the kidney! Na determines osmolarity, goljan says

As far as I know, it is in the kidney.

 

[jfgavina]

As far as I know, it is in the kidney.

yes they are, my bad.