1 00:00:02,188 --> 00:00:07,712 We're going to compare Aldosterone and ADH or Antidiuretic Hormone side by side. 2 00:00:07,712 --> 00:00:10,419 To do this I think it would be helpful if we just 3 00:00:10,419 --> 00:00:14,990 do a little recap on how these two work because it's going to help 4 00:00:14,990 --> 00:00:19,618 inform exactly what they do. 5 00:00:19,618 --> 00:00:25,393 So if we have a little nephron here, a little tubule, and these are the cells lining the tubule 6 00:00:25,393 --> 00:00:30,918 and it's going to eventually send the urine on its way out. Next to it I have a little 7 00:00:30,918 --> 00:00:37,966 blood vessel, and just to save myself from drawing it twice I'm going to cut and paste 8 00:00:37,966 --> 00:00:43,234 this over to this side right here. 9 00:00:43,234 --> 00:00:51,665 In this tubule we know that on one side, on the aldosterone side, we have water permeability. 10 00:00:51,665 --> 00:00:57,854 This membrane that seperates these two, these layer of cells are water permeable. 11 00:00:57,854 --> 00:01:02,831 Over here on the ADH side, we know that they are NOT water permeable. 12 00:01:02,831 --> 00:01:06,643 The reason I'm saying it's different is because we know that, although they look the same 13 00:01:06,643 --> 00:01:09,238 these are different parts of the nephron. 14 00:01:09,238 --> 00:01:14,457 The way that aldosterone works, the main thing it does, 15 00:01:14,457 --> 00:01:21,627 it's going to pull in sodium and spit out into the urine potassium. 16 00:01:22,382 --> 00:01:38,131 That's the main activity of aldosterone in terms of capturing sodium 17 00:01:38,131 --> 00:01:38,131 and what happens is that sodium, we know, is not permeable to membranes. 18 00:01:38,131 --> 00:01:41,858 Not able to cross membranes very easily. 19 00:01:41,858 --> 00:01:45,343 That's actually really important because if it can't cross membranes, 20 00:01:45,343 --> 00:01:51,066 then that means that it's going to contribute to tonicity because we know that 21 00:01:51,066 --> 00:01:54,492 the ions that cannot cross membranes are the ones that 22 00:01:54,492 --> 00:01:59,875 are the biggest contributors to tonicity. 23 00:01:59,875 --> 00:02:03,200 In fact, this is actually very important because potassium 24 00:02:03,200 --> 00:02:13,817 by comparison can "slightly" cross membranes. 25 00:02:13,817 --> 00:02:17,159 So if you have one ion that cannot cross membranes at all 26 00:02:17,159 --> 00:02:22,072 and you give away the ion that can slightly cross membranes, 27 00:02:22,072 --> 00:02:27,118 then your tonicity goes up because overall you're getting 28 00:02:27,118 --> 00:02:31,272 more ions that can stay in the blood vessel 29 00:02:31,272 --> 00:02:35,900 and because they can stay in the blood vessel, it can contribute to tonicity. 30 00:02:35,900 --> 00:02:39,426 Water is going to be driven into the blood vessels. 31 00:02:39,426 --> 00:02:43,895 So that's really how aldosterone is dragging water into the blood vessel 32 00:02:43,895 --> 00:02:46,230 through increased tonicity. 33 00:02:46,230 --> 00:02:51,981 By comparison, the ADH is just using water channels 34 00:02:51,981 --> 00:02:56,979 if water is unable to get across otherwise, if you through in some water channels 35 00:02:56,979 --> 00:03:01,286 then you have no problem gathering water. 36 00:03:01,286 --> 00:03:05,303 So these are the key differences: one of them uses an osmole 37 00:03:05,303 --> 00:03:09,844 to drag water across and that's why we always say "Water follows sodium." 38 00:03:09,844 --> 00:03:11,995 and the other is just using channels. 39 00:03:11,995 --> 00:03:19,887 Let me make a little bit of space here. . . let's see if we can create some space down here 40 00:03:19,887 --> 00:03:24,770 I'm going to create two categories: one category is Volume 41 00:03:24,770 --> 00:03:31,876 and the other is Osmolarity. 42 00:03:31,876 --> 00:03:42,772 We know osmolarity actually is simply a fraction. It's just osmoles divided by volume. 43 00:03:42,772 --> 00:03:48,853 We have the same thing in the other column and I'm going to do that for this side as well: 44 00:03:48,853 --> 00:03:55,373 osmolarity is osmoles divided by volume. 45 00:03:55,373 --> 00:04:04,101 We're going to see how these two work and whether one or both will be effected by the hormones. 46 00:04:04,101 --> 00:04:11,389 We know that the way that aldosterone works is by raising the osmoles. 47 00:04:11,389 --> 00:04:15,534 It's going to change this, going to increase the osmoles 48 00:04:15,534 --> 00:04:19,223 and as a result it will increase the volume. 49 00:04:19,223 --> 00:04:25,806 So actually, both osmoles and volume are effected. 50 00:04:25,806 --> 00:04:33,600 Let me start out by just circling this box because we know that the volume is effected. 51 00:04:34,200 --> 00:04:34,200 because osmoles and volume are both affected and that they're proportional to one another 52 00:04:34,200 --> 00:04:43,412 we usually don't think of osmolarity being effected by aldosterone because both 53 00:04:43,412 --> 00:04:48,864 the numerator and denominator are going to go up if there's a lot of aldosterone 54 00:04:48,864 --> 00:04:52,176 or down if there's not any aldosterone around. 55 00:04:52,176 --> 00:04:55,680 So osmolarity doesn't really get effected by aldosterone. 56 00:04:55,680 --> 00:04:58,879 Now, ADH is a little different. 57 00:04:58,879 --> 00:05:04,119 In ADH we have volume going up, that's really the primary thing that's happening 58 00:05:04,119 --> 00:05:09,006 So we'd say we have a volume change here 59 00:05:09,006 --> 00:05:13,304 but in terms of osmoles, you haven't really 60 00:05:13,304 --> 00:05:16,873 changed the osmoles with ADH, not directly. 61 00:05:16,873 --> 00:05:23,671 If you haven't changed the osmoles and you have changed the volume 62 00:05:23,671 --> 00:05:25,382 then osmolarity is changed. 63 00:05:30,445 --> 00:05:30,445 If you just change the denominator, but not the numerator then the number will change. 64 00:05:30,445 --> 00:05:30,446 So that's why ADH effects osmolarity although it doesn't effect osmoles. 65 00:05:31,846 --> 99:59:59,999 Kind of a tricky thing, but I think you can see it now 66 99:59:59,999 --> 99:59:59,999 that the numerator doesn't change, but the overall fraction does. 67 99:59:59,999 --> 99:59:59,999 So you have on this side increased volume and 68 99:59:59,999 --> 99:59:59,999 you have increased volume on this side 69 99:59:59,999 --> 99:59:59,999 and you have decreased osmolarity. 70 99:59:59,999 --> 99:59:59,999 So these are the major changes from these hormones. 71 99:59:59,999 --> 99:59:59,999 Let me make a little bit more space and we'll continue this line of reasoning. 72 99:59:59,999 --> 99:59:59,999 So if these are the changes, now imagine the scenario 73 99:59:59,999 --> 99:59:59,999 where you want to increase volume, but maintain the osmolarity. 74 99:59:59,999 --> 99:59:59,999 So if you want to increase volume, but maintain osmolarity 75 99:59:59,999 --> 99:59:59,999 which hormone would you use? 76 99:59:59,999 --> 99:59:59,999 because we can't see the hormone [drawings above], let's just use aldosterone and ADH 77 99:59:59,999 --> 99:59:59,999 and I'll just put "up" arrows and "down" arrows 78 99:59:59,999 --> 99:59:59,999 These are the two hormones, I want to increase volume, 79 99:59:59,999 --> 99:59:59,999 I would definitely use aldosterone because it 80 99:59:59,999 --> 99:59:59,999 doesn't effect osmolartiy, but I would NOT use ADH 81 99:59:59,999 --> 99:59:59,999 I'll put a little circle with a line through it. 82 99:59:59,999 --> 99:59:59,999 I would NOT use ADH because again, I want to maintain osmolarity 83 99:59:59,999 --> 99:59:59,999 I would not want to use ADH in that scenario. 84 99:59:59,999 --> 99:59:59,999 Now let's say you wanted to increase volume, REGARDLESS of osmolarity 85 99:59:59,999 --> 99:59:59,999 meaning you don't really care if osmolarity changes 86 99:59:59,999 --> 99:59:59,999 and this could be, let's say you have a big car accident 87 99:59:59,999 --> 99:59:59,999 and you're bleeding out and the only thing 88 99:59:59,999 --> 99:59:59,999 you really care about right away is increasing 89 99:59:59,999 --> 99:59:59,999 your blood volume, that's the only thing that 90 99:59:59,999 --> 99:59:59,999 matters, so you really want to increase volume and you want to do it fast. 91 99:59:59,999 --> 99:59:59,999 Well, in this scenario, you definitely want to use 92 99:59:59,999 --> 99:59:59,999 everything that's available to you, aldosterone and ADH. 93 99:59:59,999 --> 99:59:59,999 The fact the osmolarity will go down with ADH really doesn't matter 94 99:59:59,999 --> 99:59:59,999 because we said regardless in this scenario 95 99:59:59,999 --> 99:59:59,999 so because of that, I'm going to imploy ADH this time. 96 99:59:59,999 --> 99:59:59,999 You can kind of get a sense for how this is going to work, right? 97 99:59:59,999 --> 99:59:59,999 Now let's say you wanted to decrease osmlarity 98 99:59:59,999 --> 99:59:59,999 regardless of volume, so I don't really care if the 99 99:59:59,999 --> 99:59:59,999 volume changes a little bit here or there, 100 99:59:59,999 --> 99:59:59,999 so in this case, regardless of volume, what would I do? 101 99:59:59,999 --> 99:59:59,999 Well, if I didn't really care about the volume and I just wanted to decrease osmolarity 102 99:59:59,999 --> 99:59:59,999 that seems like a no brainer, right? 103 99:59:59,999 --> 99:59:59,999 That's exactly what ADH will do, it will decrease osmolarity 104 99:59:59,999 --> 99:59:59,999 and really in this case, I don't need aldosterone. 105 99:59:59,999 --> 99:59:59,999 I said in my phrase here that I don't care about volume changed so, that's fine 106 99:59:59,999 --> 99:59:59,999 I'll just use ADH and I'll tolerate the increase in volume. 107 99:59:59,999 --> 99:59:59,999 In the fourth scenario, let's say you want to decrease osmolarity and maintain 108 99:59:59,999 --> 99:59:59,999 volume, you don't want it to go up or down. 109 99:59:59,999 --> 99:59:59,999 This is kind of a tricky one right? because to decrease osmolarity, only one 110 99:59:59,999 --> 99:59:59,999 hormone will do that so you've got to start with 111 99:59:59,999 --> 99:59:59,999 some ADH, but if you want to maintain volume 112 99:59:59,999 --> 99:59:59,999 you know that ADH will cause your volume to go up 113 99:59:59,999 --> 99:59:59,999 a little bit and if you don't want it go up, you wanted to maintain volume, you 114 99:59:59,999 --> 99:59:59,999 may actually have to decrease aldosterone just 115 99:59:59,999 --> 99:59:59,999 a little smidge so that would maintain your volume. 116 99:59:59,999 --> 99:59:59,999 Now you can see how the two hormones basically 117 99:59:59,999 --> 99:59:59,999 have to work together to get the different outcomes. 118 99:59:59,999 --> 99:59:59,999 Depending on what your volume status is and what 119 99:59:59,999 --> 99:59:59,999 your osmolarity status is. 120 99:59:59,999 --> 99:59:59,999 I can flip around all the arrows or I could say 121 99:59:59,999 --> 99:59:59,999 well what about decreased volume and maintained osmolarity 122 99:59:59,999 --> 99:59:59,999 or decreased volume regardless of osmolarity? 123 99:59:59,999 --> 99:59:59,999 and you would basically just do the opposite of all these things. 124 99:59:59,999 --> 99:59:59,999 Any tweak in volume and osmolarity can help you 125 99:59:59,999 --> 99:59:59,999 predict what the aldosterone and ADH will be doing.