Dehydration (ADH release)

so in this video I want to very briefly introduce dehydration to you and also how your body responds in order cons to conserve water so in preparation for this video if you haven't already I suggest you watch some of the renal System videos specifically The Ren and angot tense and aldosterone System videos and also the fluids and electrolytes video now I want you to think about your body when it's at rest and you are sufficiently hydrated now that means that you have a sufficient amount of fluid in your body and we spoke about in the previous video that the fluid is compartmentalized into extracellular and intracellular fluid and that there's a particular concentration of this fluid and that concentration is determined by how many solutes are dissolved inside that fluid so I like to think of it as I've got a container with a certain amount of stuff dissolved inside of it so you could think of this stuff as being sugar or salt or something like that that's very similar inside of our body we have a certain concentration of sodium potassium chloride magnesium hydrogen ions uh glucose Ura and so forth okay now this concentration is measured in Milli Osmos so the concentration of your body fluids should be between 290 and 300 Milli Osmos okay that's the normal concentration and that again has to do with a balance between solutes and water so the fluid balance now think about what happens when you are no longer well hydrated so you haven't had a drink of water for maybe 12 to 16 hours and you've been doing vigorous exercise well that water that's inside of your body is either perspired or is breathed out or is burnt up through the activity of creating energy but overall it's utilized and disappears now the solutes in your body may be diminished slightly but not as much as the water in your body is which means that you have a particular concentration of solutes and water but when you start to do vigorous exercise and don't remain well hydrated the water drops far below that of the solutes and this is what I'm highlighting here so going from a hydrated state where we have just as an example 10 solutes dissolved in one liter okay we move down to where we've become dehydrated well what's happened is that the volume of the fluid is diminished yet we still have those 10 solutes so what happens then well this fluid becomes more concentrated and that's what happens to our body fluids it becomes more concentrated which means that 290 to 300 milliosmoles may get a little bit higher and go to 320 milliosmoles and remember this is kicking out of homeostasis homeostasis is between 290 to 300 M Osmos which means if it's being pushed out of homeostasis our body must respond to try and bring it back so I'm going to talk now about how our body response so first step is this if we have a look at our brain and that's a pretty dodgy looking brain but you know I'm not the best drawer all right I won't draw the rest of the brain St so we have our cereum and we uh and we have our cerebellum and we have our medulla uh we have midbrain Pond of Thea and then spinal cord okay well there's a part of our brain round about here called the hypothalmus okay and the hypothalmus has two little danglies hanging below it okay now these little danglies are the pituitary glands and I've done a video on the pituitary glands and pituitary gland hormones so if you'd like to go back and watch that please feel free but what I'm going to do is now highlight that particular area so we have the hypothalmus with the anterior and posterior ptil so let's write this down whoops hypo thus and this is the posterior pituitary gland and this is the anterior ptary GL okay why am I drawing this well remember this concentrated fluid now is floating around your entire body which means it even gets up to your brain and gets to the hypothalamus your hypothalamus has certain receptors and these receptors pick up an increase in osmolarity so remember measured in Milli Osmos which is a measurement of osmolarity which is a measurement of concentration per volume and this osmolarity is increased in so the hypothalamus measures an increase among other things measures an increase in osmolarity now this increase in osmolarity is picked up by the hypos and the hypos sends a signal now does it send it to the posterior or anterior pituitary well it sends it to the posterior pituitary gland and sending a signal to the posterior pituitary gland signals it to release one two hormones so remember there's two hormones in the posterior pituitary one is oxytocin and the other is ADH anti-diuretic hormone well today we're dealing with hydration and Water Conservation so it's going to be anti-diuretic hormone so the posterior pituitary gland now releases anti- diuretic hormone let's write that down anti- diuretic hormone so first let's talk about what that is diuretic or diuresis means to expel okay to urinate so antidiuresis is to not urinate so this hormone plays a role when it's released to stop you from peeing okay so hopefully you've already drawn or connected the dots you've G well I'm dehydrated so it wouldn't make sense for me to pee out more fluid I need to conserve the fluid that's exactly right so this dehydrated state which resulted in increased osmolarity is picked up by the hypos sends a signal to the posterior pituitary gland which releases anti-diuretic hormone into the bloodstream now this antidiuretic hormone which is now in the bloodstream where does it go to well it travels down until it gets to where does blood always ultimately end up at the kidneys specifically at the filtration unit of the kidneys which is the nephron so if I draw a nephron up and you know from watching the previous videos on the nephrons theyve are different component so remember this Blood is ultimately going to make it down to the nefron which means antidiuretics ultimately going to make it to the nephron but where specifically does antidiuretic hormone act so ADH is in here where does it act well remember you have the Bowman's capsule the proximal convoluted tubule the descending Loop of Henley the ascending limb of the loop of Henley you have the distal convoluted tubil and you have the collecting ducts so where does ADH at well ADH acts at the collecting ducts which means ADH comes along and how does it function well ADH inserts proteins into the walls of the collecting ducts these proteins are called aquaporin so what does aqua mean Aqua means water what does porin mean it means whole so it literally means water holes ADH inserts water holes into the collecting duct and what do they do well they tell water to jump back into the blood and into the body why is that important well we're keeping our water we're holding on to it cuz remember if the water stayed in this collecting duct It ultimately comes out as P so now ADH is told it to reabsorb so how does our body so this is just one way but how does our body respond to dehydration well when our blood and our intertial fluid becomes dehydrated it becomes more concentrated which means its osmolarity has increased this increased osmolarity stimulates the hypothermic to tell the posterior pituitary gland to release anti-c hor anti-diuretic hormone travels to the nefron specifically the dis the the collecting duct it inserts aquaporin proteins which tells the body to reabsorb water and we keep a hold of that water and this is our water conservation so I hope that made sense

Channel: Dr Matt & Dr Mike

Views: 145,880

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Id: CWBNzX3d_y8

Length: 9min 49sec (589 seconds)

Published: Tue Oct 11 2016