Dehydration

hi everybody dr mike here in this video we're going to talk about dehydration now dehydration is defined by a loss of total body fluid now not all dehydration is the same today i'm going to talk about two different types of dehydration one that we call intracellular dehydration and one that we call extracellular dehydration first thing you need to be aware of which i've spoken about in previous videos is that if we have a cell and have a look at all the stuff inside the cell so this may be ions like sodium or potassium or magnesium or chloride or whatever it may be and look at its concentration inside the cell compare it to the concentration of all that stuff outside the cell what you're going to find is that the concentration normally is the same this concentration is 290 milliosmoles outside the cell 290 milliosmoles inside the cell that's the same now what that basically means is that water will be moving in that direction and that direction at around about the same rate which means there's no net shifting of fluid between the intracellular compartments and extracellular compartments now remember two-thirds of your water is inside the cell one third of your water is sitting outside the cell okay when the concentration of stuff is the same inside compared to outside there's no overall net movement of fluid one way or the other however let's talk about intracellular dehydration let's just say that you do some exercise now when you exercise you obviously sweat and the reason why you sweat is because that fluid or water that's coming out of your skin is going to transfer heat away when a breeze goes past it takes heat away in actual fact about 580 kilocalories will be of heat will be taken away per kilogram of sweat how much do you sweat during exercise anywhere between 0.5 to 2 liters per hour depending on how intense you're exercising so exercise and sweat glands are a way to release this fluid these sweat glands predominantly are equine sweat glands and if you think about what is inside of it predominantly it's water right but there's also going to be some salts like sodium and chloride and magnesium and potassium and so forth now remember this in the base of these e-crime glands right so you get the base of the gland and then it snakes its way up to the skin here where it's forming the sweat it's going to contain water and the sodium and potassium and chloride and magnesium and so forth right those ions now the concentration of those things inside the sweat gland when it's being made is the same as the concentration inside the cells okay when it starts to move its way up through the gland those substances start to get actively reabsorbed back into the body and by the time you sweat and the sweat goes onto your skin the concentration of those substances inside your sweat is less than the concentration of those substances inside your cell we call that a hypotonic solution now when it's the same concentration that's called an isotonic solution you've probably heard of that before with a gatorade all it's saying is that in that gatorade that water you have a whole bunch of salts in there that's at the same concentration as your blood or your cells okay hypo means it's less concentrated than your blood or your cells hyper means it's more concentrated than your blood or your cells got it now that means you do exercise you start to sweat like i said 0.5 or 2 liters per hour of this sweat which contains some salt but what you find is most of that salt gets thrown back into your body you end up sweating or releasing more water than you do all the substances dissolved in your water so basically what's happening is this you have a container and this container has water in it and some stuff dissolved in it when you do exercise you lose a whole bunch of water and only a few of these things but significant amounts of water have been lost now think about what that means if most of and this is happening from all the fluid outside the cells right so i'm pulling out some of this water and keeping most of these dissolved substances that means this fluid outside the cell becomes more concentrated all right and if it becomes more concentrated this may jump up to 310 milliosmoles for example now if it does what that now means is there's a concentration difference from outside the cell to inside the cell and your body hates it the only way your body can fix this is by shifting fluids between the set between inside the cell to outside the cell now water will try and balance this out and it does it by moving in one direction from inside the cell to outside the cell and so it slowly drops that to 300 milliosmoles and this concentration inside rises to around about 300 milliosmoles but think about what's happened through exercise and sweating water has been taken out of our cells and those cells begin to shrink when these cells shrink that means you get intracellular dehydration intracellular dehydration that's what it's called now when these cells start to dehydrate in the brain they specifically will do this to all the cells but they specifically will do it to a cells in the hypothalamus hypothalamus picks up this change in concentration sends a signal down to the posterior portion of the hypothalamus so the posterior portion of the pituitary gland and tell it to release something called antidiuretic hormone adh adh as a hormone travels through the bloodstream goes down to the kidneys specifically goes to the nephrons i've spoken to you about the nephrons watch one of those videos if you don't know about them what adh does is it puts little holes in these tubules to tell the water that was going to turn into p to be thrown back into the blood adh increases water reabsorption and when that happens we replenish the volume of water outside pushes that water back inside all right so this is what happens in intracellular dehydration at the same time the hypothalamus will send signals to the cortex of your brain and tell you that you're thirsty and drink that means the response to intracellular dehydration will be a hormonal response adh and a behavioral response to drink now let's compare this to extracellular dehydration what's happening here is something different this is where your water loss outside your cells so again remember you're going to have a concentration of stuff outside the cell and inside the cell 290 milliosmoles 290 milliosmoles and now what happens in extracellular dehydration is the fluid outside the cells is being lost at the same concentration as what it is in outside the cell here so you're not just losing water like we were with intracellular dehydration mostly water you're losing water and the dissolved substances at the same concentration that they are here which means the whole fluid level drops but it still remains 290 milliosmoles think about it like this i've got that container with some particles in it let's say i've got 1 2 3 4 5 6 7 8 9 10 particles and 1 liter 10 particles per liter right per 1 liter let's now say i lose water and particles at the same rate so i go down to 5 particles 5 particles per half a liter five particles per half a liter is exactly the same as ten particles per one liter it's still 290 milliosmoles which means there's no concentration difference from inside the cell to outside the cell is there going to be water moving out no so the cells remain hydrated but outside the cells we've lost our fluid volume i told you in a previous video that the extracellular fluid is the same as the blood fluid which means your blood volume drops if your blood volume drops your blood pressure drops if your blood pressure drops your tissues don't get the oxygen and nutrients it needs specifically here at the kidneys at the nephrons we need to filter remember 120 mls per minute of blood if your blood pressure and volume drops that drops you don't filter your blood properly your kidneys they're not happy with this so they release a hormone called renin specifically from here at the afron arterial renin is released renin does a whole bunch of things renin does a whole bunch of things to increase blood pressure i've done a video on ren and watch that increases the blood pressure it does it by going to the brain specifically the hypothalamus and releasing adh it also tells all the blood vessels to constrict if you constrict a hose the water backs up and the pressure increases perfect that's what we want as well it releases something called aldosterone aldosterone comes from the kidneys you've got the cap on the kidneys called the adrenal gland aldosterone is produced there is released goes to the distal convoluted tubule and the collecting ducts to reabsorb salt back into the body if salt is pulled back into the body water's pulled back into the body water's pulled back into the body blood volume goes back up blood pressure goes back up and everything is sorted

Channel: Dr Matt & Dr Mike

Views: 130,003

Keywords: dehydration, fluid, balance, intracellular, extracellular, exercise, sweat, diarrhea, drugs, medications, hypothalamus, pituitary, urine, kidneys, hormones, ion, sodium, Na+

Id: JBUA1NcRchs

Length: 9min 44sec (584 seconds)

Published: Fri May 01 2020