coolest thing I learned all year

A while ago (beginning of Jan) Nava asked me to tell her something cool I learned in medical school. What I tried to explain to her via email has ended up to the coolest thing I learned all year. Below I have pasted my best explanation, which may be confusing to a certain extent, but I tried - so I impart to you the coolest thing I have learned in the past two years.



Ok, something cool I learned medically - well just about every block there is something new and interesting. I dont' know how well I will explain this via email, but I will do my best.
So the idea is that - if you have more solutes (salt, protein, glucose, etc) - in your blood than in your interstitial space (the space between your cells outside of your blood vessels) then water will flow from the interstitial space into your blood vessels until the concentration is even between the 2 sides (blood and interstitial space) and vica versa
so if you have very dilute blood (very little protein, glucose, salt, etc) then fluid will flow out of the blood vessels into the interstitial space

this is why they say a high sodium diet leads to hypertension, is because the high salt content in the blood vessels causes fluid from the interstitial space to flow into your vessels, which increases blood volume and thus blood pressure.

that isn't the cool part. So the cool part is that if you are dehydrated or have a low blood volume - then fluid from your body will flow into your blood vessels - in order to try and maintain adequate blood volume, blood pressure, and perfusion
well it would be really bad if your brain lost a lot of it's fluid, because it wouldn't function properly so in order t to keep fluid in your brain and that region (so your brain doesn't dry up like a raisin) your brain produces these idogenic osmoles in response to dehydration or losing of body fluid. These osmoles act like the other solutes (salt, glucose, protein etc) - in order to keep fluid from leaving the brain and going into the blood stream.

I hope that makes some sense.
But i just thought it was really really cool that your brain just makes these protein things to keep your brain safe.