Hypoparathyroidism

[MedPR]

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Why does decreased calcium in the extracellular fluid allow more sodium to flow through the membranes of nerve cells?

If you decrease the extracellular calcium, wouldn't that lead to a less net positive charge? Thus increasing the need to keep Na+ out of the cell and in the extracellular fluid to maintain the electron gradient?

 

[chiddler]

Haven't began with neurobio so can't help you. But where did you read that this occurs?

 

[MedPR]

Haven't began with neurobio so can't help you. But where did you read that this occurs?

TBR Bio Chapter 5, I don't remember exactly where though.

 

[SLC]

The simplest answer (keep things simple whenever you can, TRUST ME) is that there's a membrane transport protein often called the sodium/calcium anti porter. Basically it takes sodium in and releases calcium out.

So if there's low ECF calcium, then the larger than normal gradient (internal Ca++>>>external Ca++) drives this pump at a higher than normal rate.

Also, your idea about the net positive charge being less outside in the case of low ECF [Ca++] is true to an extent, but this really helps drive the pump as well as the cell can expel a 2+ charge while only taking on a 1+ charge in return. The cell thereby maintains it's charge with respect to the ECF (homeostasis).

Hope that helps.

 

[MedPR]

The simplest answer (keep things simple whenever you can, TRUST ME) is that there's a membrane transport protein often called the sodium/calcium anti porter. Basically it takes sodium in and releases calcium out.

So if there's low ECF calcium, then the larger than normal gradient (internal Ca++>>>external Ca++) drives this pump at a higher than normal rate.

Also, your idea about the net positive charge being less outside in the case of low ECF [Ca++] is true to an extent, but this really helps drive the pump as well as the cell can expel a 2+ charge while only taking on a 1+ charge in return. The cell thereby maintains it's charge with respect to the ECF (homeostasis).

Hope that helps.

Thank you! So answering the question correctly requires knowing about the Na/Ca pump.

 

[SLC]

I would think so, yes. I just finished the Neuro block at Medical School, this was what we discussed.

It's the basis behind hypoparathyroidism induced tetany. Basically: Low Ca++-->Increased Na+ entry (action potentials)--->increased muscle contraction, often to the point of severe cramping or tetany.

 

[MedPR]

I would think so, yes. I just finished the Neuro block at Medical School, this was what we discussed.

It's the basis behind hypoparathyroidism induced tetany. Basically: Low Ca++-->Increased Na+ entry (action potentials)--->increased muscle contraction, often to the point of severe cramping or tetany.

Yea that's exactly what the rest of the explanation said. Glad you are lurking here in the pre-med boards 🙂

 

[SLC]

Yea that's exactly what the rest of the explanation said. Glad you are lurking here in the pre-med boards 🙂

I like to pay it forward when I can. I should be studying, but helping people out is a nice break here and there.

I'm in the middle of acid-base disturbance so if that stuff comes up It'll be fresh in my mind!