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Video transcript

I'm here at Stanford Medical School with Neil gesundheit who's a faculty medical T member here at the med school hi so what are we going to talk about well the topic for today is endocrinology which is the study of hormones and the word hormone is derived from the Greek word which means aroused the activity and what hormones do is their chemical messengers that are made at one part of the body and typically go to another part of the body too as suggested arouse the activity and give function to another organ so that they are essentially kind of signaling a way to communicate between one part of the body and the other exactly they're very sophisticated communicators I think that's a perfect term and I think the other way to think of it as our body communicates in some ways directly for instance nerves innervate muscle right and when you want to contract your muscle you give a signal from your brain it goes down the nerve and it directly attaches to the muscle and causes it to contract whereas hormones are more like the Wi-Fi of the human body they're Wireless they are made at one place they go into the bloodstream which is like the airwaves if you will and then they they work on another part of the body at a distance without a relay without directly connecting to that part of the body mechanically and our hormones are they a specific type of protein or a specific type of chemical or they're really anything that does what you just described it's pretty much anything that they fall into two major categories they're small molecules that typically derive from amino acids and those molecules are just Oh 300 to 500 and most Dalton's which are molecular mass units okay up to large proteins that can be hundreds and hundreds of amino acids in size I see so anything anything that really has a signaling function that's right would be considered a hormone right and the other thing is we talk about hormones and three sort of subcategories we call some of them endocrine hormones where they really get into the bloodstream and work at a far distance and we'll give some examples with your diagram right there in just a minute but there are others that are called paracrine hormones and paracrine hormones are more regionally active so they might be made let's say in one part of the body and work within a small distance of that site of synthesis and then the third category which is less common would be autocrine hormones and the autocrine hormones are actually made directly at one cell and work on that same cell or in the cell right next door in a very very small distance I see are these things you know when you work so the endocrine hormones like I think I have a mental model for it they're kind of released and far away in the body someplace if they're picked up by the right receptor they'll have the right function the paracrine hormones is their effect small because they only are able to travel a small distance or is it something else typically the paracrine hormones um do get into the bloodstream but the concentration of the receptor the receiving end as you suggested is right close by so it tends to make a paracrine hormones work regionally is that the high concentration of the receptors are very close to the site of synthesis I see I see and the same with autocrine is often they're made and there's a very high concentration of the receiving end right at that cell right next to that cell and this might be a silly question but it's called endocrinology are there other power chronologist well I I it's a good point I don't think so I think we just perhaps because the parent function of hormones was discovered later I still carry this all under the umbrella of endocrinology right so the all hormones is endocrinology even though endocrine hormones are the ones that act at far distances that's right I think that's a good way to summarize it now I like the diagram that you created here because it illustrates some of the major endocrine organs the ones we'll be focusing on in later lectures so the first one that you showed very nicely in the head at the base of the brain is that orange structure and that would be the pituitary gland that's right and the pituitary gland is called the master gland because from the pituitary we make hormones that work on yet other organs right so I'll give you an example one of the hormones that's made by the pituitary is called thyroid stimulating hormone or TSH and after it leaves the pituitary it goes into the circulation and it acts on the thyroid gland where there are high receptors for TSH on the surface of the thyroid and it stimulates the thyroid gland to make thyroid hormone typically thyroxine t4 or triiodothyronine t3 those would be the two main circulating thyroid hormones and what are those do those regulate metabolism they regulate appetite that regulate thermogenesis they regulate muscle function they have widespread activities on other parts of the body but it kind of up regulates your downriggers the entire body and the metabolism that's right so someone with hyperthyroidism would have very high metabolism you may know the classic picture of some with a high heart rate rapid metabolism weight loss that would be some with excess amounts of thyroid hormone and then you see pretty much the inverse picture when someone has a deficiency of thyroid hormone and some with hypothyroidism so it's critical to maintain just the right amount of almost all of these hormones and the thyroid hormones are good examples but the ultimate regulation is from that pituitary right this is kind of the master one it sends a signal there then that kind of that's right and we'll talk later about feedback loops because how does the pituitary know when to stop making TSH and basically like a thermostat it can sense the levels of thyroid hormone and when those levels are just at the right level and not too high it'll decrease the amount of TSH it makes if the levels are too low it'll increase TSA to try to stimulate the thyroid glands you may get more thyroid hormone very cool what else do we have okay so the other hormone some of the major wants the pituitary in addition to making the thyroid stimulating hormones it makes a hormone called ACTH adrenocorticotropic hormone which acts on the adrenal cortex and the adrenal is that gland exactly it sits on top of the kidney and the outer layers of the adrenal gland are the adrenal cortex and those are stimulated by ACTH and they don't they're not related to the kidney they just sit on top there there's actually they're right there they're related only in that sense that they the blood supply is rich like the kidneys breads blood supply and they happen to sit above the kidney and they're called adrenal because they're adjacent to the kidney renal part that should have been obvious and revised but they don't per se and you know filter blood or do any of the key functions that the kidney sub serves I see and what what are the what's their role so the adrenal glands make the adrenal hormones like cortisol which regulates glucose metabolism it is important to maintaining blood pressure and well-being and then it makes mineralocorticoids like aldosterone which is important for regulating salt and water balance you also have adrenal androgens which are somewhat important and those 3 hormones are the main hormones made by the adrenal cortex I see the ACTH primarily regulates the cortisol and the adrenal androgens and there's another system that regulates the mineral accords that we'll talk about later ok and we have a few more organs here yeah so also out of the pituitary we make loot luteinizing hormone and follicle stimulating hormone those would be abbreviated LH and FSH LH and FSH and those act on the gonads so in the male it will act on the testes and the female it will act on the ovaries to stimulate the development of sperm in the male and a sites or eggs in the female and also the production of gonadal steroids primarily testosterone in the male and estradiol in the female right right and are we missing anything well there are two other hormones that also derived from the anterior pituitary and those would be growth hormone that's critical for optimal growth of long bones maturity really does do a lot it does yeah and so that would say she would drive human growth hormone growth hormone and that would act on long bones for instance and then we would have prolactin which is important in women for lactation being able to breastfeed after delivery and insulin is insulin is key but it doesn't come from the pituitary so now we're going to work our way down a little right we talked about the thyroid gland making thyroid hormone and then when you get to the pancreas which is that yellow structure right in the middle inside the pancreas there are small islands called the islets of langerhans and the islets within the pancreas make endocrine hormones like insulin and glucagon but insulin is vital without insulin you have diabetes right and with out insulin you don't transport glucose into muscle and remove glucose from the bloodstream normally right and that the absence of insulin can produce all the symptoms of diabetes that we'll talk about later right it seems just structurally of the pancreas right here you have the adrenal glands right there that they're all near those kind of that interchange on the because they're also important - yeah get to where they need to get that's a good observation they all have a lot of venous drainage from them so that when they make their hormone it gets into the bloodstream rather quickly because they are vital structures very cool so I think I think we could leave it there and then in the next video you have some pictures I think would be pretty interesting okay yeah in the next video we'll talk about sort of how you have to have the right amount of the hormone or else things go awry very cool thanks a bunch okay thank you