Transcript for:
Overview of the Endocrine System

in this video we're going to look at the endocrine system we're going to start by doing an overview of the endocrine system comparing endocrine and exocrine glands and the endocrine system to the nervous system the first thing that we want to talk about are four different types of principal communication mechanisms the first one is Gap Junctions Gap Junctions are when we have cellto cell communication and the cells will have pore in them which allow chemical Messengers nutrients molecules to go back and forth and communicate between two cells second type of communication are neurotransmitters which you've seen before in bio21 neurotransmitters are chemicals that are released from a neuron and then the two that we're going to focus on with the ocrm system are paracrine and um hormones parrens are also sometimes called local hormones paracin are a chemical that is secreted by one cell into a tissue fluid and so it can affect the cells that are nearby in that tissue most of what we're going to talk about are hormones and hormones are chemical Messengers and the thing that makes them different from the others is that they are secreted into the blood so we're going to have our cell is going to secrete the hormone and that hormone that chemical Messer is going to go into the bloodstream and then it can travel throughout the body to wherever the blood goes so the inine system is composed of the glands tissues and cells that secrete the hormones and then we look at the physiology of the hormones Endocrinology is the study and diagnosis and treatment of disorders and then we also look at the endocrine glands which are where the hormones are produced so if we're looking at the endocrine glands just kind of a brief overview for you um in the brain we start with the pineal gland we also have the hypothalamus and the pituitary then we have the thyroid gland on the posterior side of the thyroid gland are the parathyroid glands then we have the thymus the adrenal glands that are on top of the kidneys the pancreas and then the gonads the testes or the ovaries we are going to go through each of these glands and the hormones that they produce so when we're looking at our glands we have two or three depending on how you want to classify it classifications um so a gland can be defined as an exocrine gland and the thing that defines it as an exrr gland is that it has has a duct so it has some sort of tube that's going to carry the secretion so in the pancreas just drew that completely wrong in the pancreas it's like this okay do an upside down pancreas in the pancreas we have a tube called the pancreatic duct and it will carry the digestive enzymes and secretions from the pancreas into the small intestine and so that is exocrine what we're going to focus on are the endocrine glands and they do not have ducks and again they don't have Ducks because we're using the bloodstream to transport the hormone now we do have a third classification which is where we can have organs that are both exocrine and endocrine um examples of that are the pancreas and the gonads and so they will have both um and actually the gonads because they do hormones and cells so and the pancreas does those digestive enzymes which are exocrine but then it also does endocrine secretions insulin and glucagon all right then looking at the nervous system and the endocrine system the reason that we're going to talk about nervous and endocrine system is because those are our two control systems right and they have um they have to communicate to each other and so they work they work together um and so they have some similarities and some differences and so for the differences primarily what I think of the differences is it has to do with speed um and so the endocrine system is our fast it's like a cat supposed to be bunny IND the nervous system is supposed to be fast right so it reacts really quickly milliseconds okay starts and stop quickly it adapts quickly um it uses that electrical signal right our Act potential um and then because our nervous system right the the neurotransmitter is released at an axon terminal it can only affect the tissue that is right there and so it is a targeted and specific response all right whereas our endocrine system reacts much more slowly so it's more it's more like a a turtle it reacts much slower than our nervous system it's slow to start or stop it may take a while to remove those hormones from the blood okay um and it uses a chemical response those are the hormones and again because the hormones are going into the blood it's going to have a more General more widespread effect meaning that we can um impact multiple organs with a hormone now some of the things that they have in common is that some of the chemicals function as both okay so like epinephrine epinephrine secreted from uh sympathetic neuron is the same chemical that is secreted from the Adrenal medulla their effects is are the same just how widespread it goes may be different okay um another thing that they have in common again is the the two systems regulate each other so they work together and then the third thing is that we may have these neuroendocrine cells and we'll see this with the um hypothalmus and the posterior pituitary where we use both where we're going to combine we're kind of going to mash up the nervous system and the endocrine system so when we're talking about the endocrine system we said a bunch of times already that the hormone goes into the blood well the blood goes to all tissues of your body but we know that not all tissues of your body respond to every hormone and so what prevents that from happening or what specializes those are these target cells or Target organs and the the responsible party here is the receptors so think about the receptors as having like a three-dimensional shape okay I use geometric shapes because that's what my brain can wrap around so we have a cell here and we have square hormone and we have Circle hormone and we have triangle hormone all floating in our bloodstream next to this cell okay this cell only has Square receptors so it can only bind Square hor hormone therefore it does not respond to Circle hormone or triangular hormone so it is only a target for square hormone now cells can have multiple receptors so now this cell is a target for square hormone and circle hormone okay but the key here is that a target for a hormone has The receptors for that hormone and is therefore able to cause some sort of change recognize that hormone and then cause a change so again just reminding nervous system really quick right uses that electrical action potential it's going to be local and targeted because it's only going to have its effect at the end of that neuron endocrine system slower it's slow to produce the hormone it has to travel in the blood it can it's slow to turn off the signal because we have to remove the hormone from the blood you have to clear the hormone from the blood but it can have a more widespread or general effect because it's going in the blood it can impact multiple organs the next thing that we want to start looking at is the hypothalmus and the pituitary gland we are going to look at all glands there is the endocrine gland table if you want to fill that out as you go through this that has the glands the hormones the targets and the functions so when we're looking at the hypothalamus the hypothalamus is a w shape okay like a flattened fun funnel all right it is about the size of your thumbnail so it's pretty small okay it's almost right in the middle middle middle of your brain it is connected to the pituitary by a stock called the infundibulum and then the pituitary gland is is about the size of the kidney bean and it is actually made up of two loes the anterior and posterior pituitary anterior and posterior pituitary embryonically come from two different places the anterior pituitary embryonically comes from the ferx which is your throat a little piece of the ferx gets pinched off and that bud travels up and sticks next to the posterior pituitary whereas the posterior pituitary is a downgrowth of the brain that's going to form the posterior lobe of the pituitary gland so because they are different embryonic origin they're actually different tissue types and therefore they communicate with the hypothalamus differently so the anterior pituitary is also called the adino hypothesis the A's go together remember this is from the ferx embryonically so it is glandular epithelial tissue okay because it is it is glandular tissue and glands secrete hormones and hormones go into the blood the connection between the hypothalmus and the anterior pituitary is blood vessels and that is called the hypo hypophysial portal system now remember the posterior p plary it is also called the neuro hypothesis and so the neuro hypothesis reminds us that embryonically it comes from the brain and therefore it is nervous tissue and we remember from bio201 that nervous tissue uses neurons to communicate and so that is going to use the hypothal hypophysial tract so those are neurons to communicate from the hypothalamus to the posterior pituitary so again just looking at here are the two nuclei so the superior one is the pair of ventricular nuclei the inferior one is the Supra optic nuclei and you can see the axons going down and so this makes up the hypothal hypophysial tract that connects the hypothalamus to the posterior pituitary on this other picture you can see the hypothalamus and you can see the blood vessels that are going around the anterior pituitary this makes up the hypothal portal and that connects the hypothalmus to the anterior pituitary all right right so let's start looking at some hormones and start talking about hormone function so the hypothalamus actually makes eight hormones six go through the hypothal portal and two the anterior pituitary okay so these six hormones travel through the hypoth the seal portal to the anterior pituitary and they're going to control the secretions of the anterior pituitary glands the other two hypothalmic hormones are made in the hypothalamus so they're made in those nuclei and then they are secreted from the posterior pituitary so we'll talk about those in a minute so looking at our F hypo IC hormones that go to the anterior pituitary we have two different two main types we have two we have releasing hormones and the releasing hormones are going to stimulate hormone release from the anterior pituitary okay so you have four releasing hormones and then we have two inhibiting hormones and they are going to inhibit or stop hormone release from the anterior pituitary so on your endocrine gland table hypothalmic hormones the six releasing and inhibiting hormones all have the same Target and the target for all of them is the anterior pituitary the function of each then is specialized based off of its name so gatot tropen releasing hormone will cause the release of the gatot tropins FSH and LH thyrotropin releasing hormone causes the release of the thyroid hormones T3 and T4 prolactin inhibiting hormone causes the inhibition or stop production of prolactin so you can see all of the right so CR will cause the release of act ghrh will cause the release of growth hormone and then somatostatin will inhibit grow growth hormone and thyroid stimulating hormone okay so hypothalmic releasing and inhibiting hormones all go to the anterior pituitary and either cause the release or inhibition of a specific hormone or hormones the other two hypothalmic hormones that are stored in the posterior pituitary okay so they are made in the hypothalamus and stored in the posterior pituitary are oxytocin and antidiuretic hormone the target for oxytocin are the uterus and mamory glands and oxytocin will stimulate labor contractions or cause milk release oxytocin is produced by the par ventricular nuclei of the hypothalmus so I remember pot par ventricular nuclei makes oxytocin the second hormone is antidiuretic hormone the target for anti-diuretic hormone is the kidneys the function is that it retains water ADH is secreted by the super optic nuclei of the hypothalmus so I remember sad with a h because it's so sad okay so ADH is secreted by the super optic nuclei of the hypothalamus again these are classified as hypothalmic hormones because they are made in the hypothalamus and then stored and released via that neuroendocrine reflex from the posterior pituitary okay so looking at our histology of our pituitary gland you can see the histology reflects those embryonic differences so this top picture is the anterior pituitary lots of cells okay this is that uh epithelial glandular tissue lots of cells lots of dark nuclei so it actually stains very dark that is the anterior pituitary posterior pituitary stains much lighter you have some smaller dark nuclei those are the neurog gal cells right because this is nervous tissue and then you have the hormones stored in the nerve endings and then you have nerve fibers so it's much lighter because it's that nervous tissue so there's not as many cells and nuclei to absorb the stain and that's the posterior pituitary okay the anterior pituitary hormones the anterior pituitary also makes six hormones and those are going to be again regulated through those hypothalmic hormones going through the hypophysial portal so we have FSH the target for FSH are is the go so either the ovaries or tesses the function of FSH is gamt production and so for females it's going to cause development of follicles which is what contains the oite or the Egg and for males it's going to cause sperm production lutenizing hormone also Target is the gonads okay because FSH and LH both Target the gonads they are called gonadotropins because that's the target okay LH function in the female is to cause ovulation and in the male LH will increase testosterone secretion please be careful FSH and LH do have two functions because they do two different things and because of the two different genders okay all right so another anterior pituitary hormone is thyroid stimulating hormone okay so the target is the thyroid gland and the function is that it stimulates secretion of thyroid hormone the last three anterior pituitary hormones are adrenocorticotropic hormone adrenocorticotropic hormone okay so the target is adrenal cortex function is that it will secrete glucocorticoids then we have prolactin like lactation so Target is the mamory glands function is to synthesiz milk and then the last one is growth hormone um and so it targets many organs so this is one you could almost call it systemic okay um and its function is to stimulate mitosis and cellular differentiation which is going to cause tissue growth or repair of damaged tissues all right so let's put the pieces together let's put the hypothalmic and pituitary hormone pieces together all right so let's look here the hypothalamic hormones so if you follow the line for each color so TR is thyrotropin releasing hormone from the hypothalmus it goes through the hypothal portal and it will actually stimulate the release of both prolactin and TSA H from the anterior pituitary if you look at the green one here GnRH so that is gatot tropen releasing hormone from the hypothalamus through the hypothal portal to the anterior pituitary to release LH and FSH which Target the gonads looking at the blue line here corticotropic releasing hormone from the hypothalamus travels through the hypothesis SE portal to the anterior pituitary to release act which goes to the adrenal cortex and then the last one growth hormone releasing hormone from the hypothalamus travels through the hypothal portal to the anterior pituitary to release growth hormone which then has multiple targets to do um mitosis and cellular differentiation for cell growth so what I want you to see with this hypo alic pituitary Target is you have you start with the hypothalamus then it goes to the anterior pituitary then it goes to a third organ like the thyroid right so like you have TR from the hypothalamus which causes TSH release from the anterior pituitary which is going to cause thyroid hormone T3 T4 for release from the thyroid gland so you can see that these Pathways all right between the hypothalmus pituitary and then a third organ um and it's important for functionality that this these pathways are completed correctly otherwise we can have hypo or hyp secretion of specific hormones all right let's go back and look at the posterior pituitary hormones now we've talked about these already they were classified as hypothalmic hormones now they are also posterior pituitary hormones because that is where they are released from okay and again this is that neuroendocrine reflex they are released when the hypothalmic neurons are stimulated okay so they are both hypothalmic and posterior pituitary hormones function is the same okay a ADH targets the kidneys function is to increase water retention it's also called Arginine vasopressin or we just call it vasopressin for short um because it can also Vaso constrict or or make your blood vessel diameter smaller all right and then the other one we talked about before again is oxytocin um it does have a variety of functions remain talked about that it will do labor contractions and milk flow so it's going to Target the uterus and the mamory glands also it does serve an important function in the brain so I'm just going to say brain we're not going to spe specify um wear in the brain but the function here is the emotional bonding all right and so that's between partners and also between mother and baby during nursing all right so let's talk about this let's look at this neuroendocrine reflex a little bit more okay um anterior pituitary is monitored by hypothalmic and cerebral control it's going to monitor the conditions um it's going to take in those stimuli and then and then either do the releasing hormone if we need more of a hormone to stimulate it or we can inhibit if we need to stop making a hormone okay so that's just your typical negative feedback that you're fairly used to um posterior Peary is a little bit different because it is that neuroendocrine reflex um so again we're going to have the stimulus so either osmo receptors or a baby suckling during nursing that is going to trigger those hypothalmic neurons to be stimulated and then that will cause the release of either ADH or oxytocin all right most of our hormone control is negative feedback you should be familiar with negative feedback remember negative feedback is going to get us back to our normal range so if something is too high we're going to decrease it so it goes back to normal if it's too low we're going to increase it so it goes back to the normal range okay so most of our hormone control is through that negative feedback um some of it is through positive feedback really the only example of positive feedback is oxytocin during labor we don't want that process to stop until that um neonate is expelled right from the uterus and the birth canal and so we want that positive feedback to continue those uterine contractions and keep increasing oxytocin to keep increasing contractions so that we can get expulsion of the fetus not we don't want that to stop all right so again negative feedback control you should be pretty familiar with this right so TR from the hypothalamus goes through the hypothal portal to the anterior pituitary which causes TSH to be released which goes to the thyroid gland to cause thyroid hormones to be secreted which is going to increase our metabolism now if because this is being secreted it's also going to go back to the anterior pituitary and the hypothalmus and send them signals that are like hey we we Secret it and so that can inhibit it so that we don't keep secreting excess thyroid hormone in this section we're going to continue talking about the other endocrine glands and so we'll just keep moving through the table looking at the Target and the function of the other endocrine glands so the pineal gland is the other gland that was located in the brain um it is also very small it's attached to the roof of the third uh ventricle it does undergo what's called involution so it does shrink all right the function is to secrete melatonin okay um and the target we'll just say we'll just say the target is going to be the brain um because it does impact those circadian rhythms in your sleep wake cycle and those types of things we won't name specific brain areas okay the thymus the thymus is also another organ that under goes involution it's very big in infants and it shrinks as we get older as well okay we'll talk about the thymus again when we talk about the lymphatic and immune system because its primary function is immune defense and so the the thop potin thymosin and Thulin all of those their function is to do that immune defense and so the target for thyroid is we can just say immune cells lymphatic organs okay but it's going to help boost our development of our of our tea cells specifically so here you can see the difference like I said it under goes Evolution so this is a newborn so all of this here is the thymus really really big it under goes that involution so it shrinks and gets really small in an adult okay thyroid gland next to our trachea just below our layer neck it is um Bob it kind of looks like a butterfly okay um it is actually pretty in real life a dark red color because it's got a rich blood supply if you look at the so the wings of the butterfly are the loes of the thyroid and then the connecting Peach here is the Estus if you look at the um histology of it okay we have these big round structures these are follicles they're surrounded by the follicular cells and then the light pink is the colloid and that's where the T3 T4 is so the thyroid hormones so then you also see outside the follicle you have these bigger cells that kind of have these clear areas those are paricular cells and they're going to secrete calcitonin so let's go back up and talk about our hormones okay so thyroid gland excuse me thyroid gland hormones so we have thyroid hormone which is our thyroxine T4 or triot thyine T3 okay but when we you can just call them thyroid hormones we're talking about T3 and T4 okay okay um Target this is another one that has a lot of targets so I kind of just say it's one that's systemic main function is that increases metabolic rate so the other things that happen are just a byproduct of that increased metabolic rate so increased oxygen consumption heat production burns more calories increases appetite okay so those are byproduct byproducts of that increase metabolism so thyroid hormone Target is systemic function is increased metabolism now don't forget that the thyroid also secretes calcitonin it also secretes calcitonin okay calcitonin and the target are the bones okay and it is going to help lower your blood calcium level and it does that by stimulating osteoblast activity all right don't forget thyroid gland makes thyroid hormones T3 T4 and calcitonin par thyroid glands are glands on the posterior side of the thyroid gland there are four to sixish on the posterior side okay um their hystology looks distinctly different they are also kind of dark orange brownish color Okay um and the parathyroid gland makes parathyroid hormone the target for this is bones and I mean if you want we can say digestive system the function is the parathyroid hormone will increase your blood calcium levels so parathyroid hormone and calcitonin have opposite effects they are what we call antagonistic hormones because they have opposite effects so here you can see on the back side of our thyroid gland you have your parathyroid glands and the hystology looks much much much different than the thyroid okay the adrenal glands then sit on the kidney we have the cortex and the medulla of the adrenal gland the cortex is the outer portion and the the medulla is the middle portion so you can see here this is the cortex the inner portion is the medulla the cortex is made up of three zones zon of glomerulosa zon of ficula zon of reticularis and then you have the Adrenal medulla the Adrenal medulla will secrete hormones that are similar to our fight ORF flight okay so epinephrine norepinephrine all right so our sympathetic nervous system um may or may not remember it is innervated by sympathetic pre ganglionic fiber so it does act as a postganglionic fiber by secreting the epinephrine and norepinephrine right so if we look at the Adrenal medulla right the epinephrine and norepinephrine those catacol Mees okay um kind of summarize if you kind of want to summarize what their effect is it's the same as your sympathetic nervous system so this is kind of your fight ORF flight response right increases alert alertness prepares you for physical activity uses fuel right so it's going to promote the breakdown of glycogen to glucose so we have fuel okay it's going to increase our blood pressure our heart rate our respiratory rate blood flow right and then inhibit digestion and urinary so again sumarize the function is our fight ORF flight response and then the target for the Adrenal medulla hormones would again be kind of systemic right the adrenal cortex then we talked about has those three different zones each Zone produces a slightly a different type of hormone so that's why we specify that so the zonic glomerulosa that's the outer layer it's going to secrete our mineral corticoids which is primarily going to be aldosterone talk about that in a minute the zon of faladin is that thicker middle layer um and it's primarily going to secrete our gluco cortic oids and that's primarily cortisol um and it will do uh androgens so some of those sex hormones sex steroids and then our last one is the Zona reticularis and it does more of our sex steroids although it does also does do some gluc corys as well okay so again those three layers gulosa decula and reticularis all right so aldosterone um the function of aldosterone is to retain sodium and water function the target is the kidneys when we retain sodium and water we will increase blood volume volum and blood pressure we'll talk about aldosterone a lot so remember what it does Cortisol cortisol has many many effects okay um it will stimulate fat and protein catabolism so if we are running out of fuel it will use those as alternative fuel sources really what I want to think about cortisol is I want you to think its main function is kind of to adapt to stress it does also have anti-inflammatory effect which is why it's used as a topical cream and a steroid injection um but kind of a catch 22 is if we overuse it overuse it it can actually suppress the immune system and make you susceptible to infection um so so cortisol function really I want you to think stress Target again kind of systemic all right um and then we have the sex steroids so androgens um and then we also do a small amount of estrog or estrogen okay um they are going to function kind of right is this stimulates the changes that we see in puberty also reproductive development and liido or sex drive so the target for these are going to be reproductive organs right all right moving on to the pancreas again we talked about this at the beginning it is both an exocrine and endocrine most of its job is actually exocrine so its primary primary job is really in the digestive function um but because of diabetes malius everybody knows about pancreas and Insulin right um but really the pancreatic eyelets that do the that regulate blood glucose here's a pancreatic eyelet only make up about 2% of the pancreas the rest of it is that exocrine function that does digestive juices within the pancreatic eyelet we have we're going to focus primarily on Alpha and beta cells the alpha cells okay this is on your table produce glucagon okay and glucagon is going to increase blood glucose so this is released between meals okay um and it is going to Target liver adapost tissue primarily all right now the antagonistic hormone is insulin insulin is secreted by the beta cells okay it's going to secrete insulin insulin is going to decrease blood glucose so this is after we eat all right and it's going to stimulate our cells so that we can absorb um glucose all right so Target I mean you could use the same targets um um that we use for glucose for glycogen um or you could say that the target is kind of systemic because all cells need glucose because all cells need energy and then we do also have these Delta or samatos satin cells that secrete somatostatin and then PP cells or pancreatic polypeptide cells um or PP cells sorry the secrete pancreatic polypeptide um that's going to help control pancreatic secretions during digestion primarily we're going to focus on the alpha and beta cells and the glucagon and Insulin all right finally the gonads um again they are both exocrine and endocrine um the exocrine products are eggs and sperm and then endocrine are the hormones which are mostly the steroid hormones so the ovarian hormones are estrogen estrad progesterone and inhibin and the testicular hormones are primarily going to be testosterone weaker androgens some estrogens and inhibit as well okay so ovarian hormones um estrogen and progesterone are going to work together to do our normal cycling and um egg development um and our normal cell cycle okay um our our normal menstrual cycling ovarian cycling producing follicles ovulation having a corpus ludum we'll talk more about this when we do um uh reproductive system if you want you can just like reproductive functions right and then the target would be the reproductive system obviously okay um so again regulates that menstrual cycle um also development of reproductive system and secondary sex characteristics as well all right and here you can see we have a ovary this one has a nice big follicle nice follicle it's ready to ovulate okay and here's the O site with the egg kind of looks like a chicken egg really all right testosterone then um testosterone is going to do I mean similar to estrogen but in males right it's going to do sperm production and then also does the secondary sex characteristics so those are kind of the functions right sperm production and reproductive system development sex drive liido and the target here again is going to be the reproductive system right and reproductive organs and this is just maintains you know the reproductive system throughout your life and here we can see testes um so you have this giant big circle which is called the siminers tubules and the sperm are developing within that all right now that we've learned about the glands and the hormones we need to talk about the different hormone types and look at more specifically the physiology of the hormones and so we're going to look at hormones and their actions so we have three chemical classes of hormones um so all the hormones that we just talked about and all of those glands we just went through belong to one of these three steroid hormone or three chemical classes so they are either a steroid hormone or they are a monoamine or they are a peptide hormone now you may see monoamines and peptides classified together because they are both from made from amino acids so our steroid hormones are made from cholesterol okay so that's like your sex steroids and our monoamines and our peptides are made from amino acids so their structure is different um and this will impact how they are then transported through the blood how they respond to target cells okay so the peptide hormones are chains of amino acids and so that's um pituitary hormones insulin and so you can kind of see here the differences then our steroids are all derived from cholesterol CH cholesterol has a five ring struct or four ring structure 1 two 3 4 1 two 3 4 and we see that in our steroid hormones they all have a similar not identical but a similar for ring structure our monoamines then are derived from a single so mono is one so single amino acid um like thyroxine epinephrine um and then our peptides these are all chains of amino acids so insulin and oxytocin for example are peptide hormones so again steroid hormones from cholesterol so they all have that same four ring steroid background backbone but again it's similar not identical they have different functional groups off of them they have double bonds um right so like estradi has three double bonds here okay um but similar for ring structure and then the functional groups off of them and some of these double Bonds in the ring structure make each of these sex steroids that are derived from cholesterol a little bit different our peptide hormones right remember peptides are proteins so they are made the same way as any other any of our proteins gen is transcribed from the MRNA it is assembled the amino acids at the ribosome and then it's going to be folded and packaged modified through the ru and the GGI apparatus so an example of that is insulin um and our peptide hormones may also have inactive active forms and so you can see that here in insulin this Pro insulin is actually an inactive form we going to remove this connecting peptide and get our true insulin which is the active form of that hormone monoamines are synthesized from the amino acids um and so we just going to hook them together if we need to to make them um so melatonin and and our thyroid um thyroid is probably going complex right we're going to link them with iodine um I do want to talk just for a minute please don't you get bogged down by the details here but I do want you to see that we need iodine okay so T3 has three iodine molecules and T4 has four iodine molecules um I do want you to see that we need health we need iodine to be able to produce T3 and T4 that is important so how do we regulate these secretions we said this is regulated primarily through that negative feedback but where that stimuli comes from could be one of three different sources right so some are the Circ Rhythm like melatonin some are on a monthly um cycle like the ovarian cycle so that would be like estrogen and progesterone um and then others are controlled just by that regular negative feedback that could come from um the stimuli could come from the nervous system it could come from another hormone or humoral stimuli meaning that it's looking for some sort of stimulus in the blood like blood calcium level or blood GL blood glucose level so let's talk about them in a little bit more detail all right so the neural stimuli we're going to have nerve fibers that Supply the endocrine glands like the sympathetic nervous system and the Adrenal medulla all right and so when that neuron is stimulated it's going to stimulate the gland to secrete the hormone hormonal stimuli we talked about this a lot we saw this connection between the hypothalmus and the anterior pituitary so a hor the hypothalamus makes a hormone it is secreted goes through that hypophysial portal to the anterior pituitary which then controls the anterior pituitary secretions of another hormone and then the third one is that humoral stimuli and that's going to be some factor that is in the blood and again we talked about like blood glucose level blood calcium level um blood osmolarity is another example all right can't emphasize this enough right the hormones travel in the blood your blood plasma is primarily water okay and because of the hormone structures they will travel differently in the blood so the monoamines and peptides are amino acids they are hydrophilic remember hydrophilic means that they love water so they can mix easily with the blood plasma so they can travel freely in the blood okay that is different for our steroid hormones and the thyroid hormones they are hydrophobic remember hydrophobic means that they do not like water they are afraid of it therefore they need a helper okay they need a helper to get through the blood and the plasma and so they will bind to transport proteins okay those transport proteins then will safely take the steroid and th thyroid hormones through the blood this also protects those hormones from being broken down by the liver and filtered out through the kidney and then once they get to their target some of them are going to become free or Unbound those are going to release and go to the Target cell all right now once they get to the Target cell whether they travel freely in the blood if they're a monoamine or peptide or if they travel bound to a protein if it's a steroid or thyroid hormone once they get to the Target cell they have to bind to The receptors to be able to cause whatever change they need to cause all right remember the receptor is like the switch that turns this metabolic pathway on or off our receptors we already talked about have specificity so they will only bind a specific hormone but they can also have this second um characteristic which is called saturation meaning that all the receptor molecules are occupied by that hormone so hormone receptors and modes of action again are primarily this is primarily going to depend on its structure so our peptides monoamines again they are hydrophilic they love water but means that they can't go through the cell membrane because remember the cell membrane is lipids okay they can't go through the cell membrane so their receptors are on the surface and then they're going to activate a second messenger system you should be familiar with second messenger systems from General biology these are relatively quick uh when compared to the steroid hormones okay so let's look so here is our peptide or our monoamine it travels freely in the blood because it likes water but it can't pass through the cell membrane so its receptor is on the cell membrane this activates a second messenger system the second messenger system is going to activate our and pathway and turn on or off this metabolic pathway all right now a little bit different for our steroid hormones so here's another second messenger system cyclic as the second messenger system here's dag and I P3 if you need a reminder of those second messenger systems okay don't get bogged down by the details but it did want you just to have those in case you needed a refresher now steroid hormones they are hydrophobic they don't like water but they like lipids which means that they can penetrate our cell membrane so their receptors are going to be in the nucleus or the cytool but they're going to be inside the cell okay now this takes a little bit longer because once it binds to the receptor it's going to activate that Target Gene and so it it takes it takes time to then um transcribe and translate that Gene into a protein so if we look at our steroid hormone it is hydrophobic it should be bound traveling through the blood the free steroid hormone is going to come it's going to go through our cell it's going to bind to the receptor in the nucleus that's going to initiate transcription and translation to get us to our protein which is then going to turn on or off a metabolic pathway all right you ever had hormones tested you know that the hormone levels are measured very small we measure hormone levels in nanograms per milliliter so we're talking about teeny teeny teeny teeny teeny teeny teeny tiny amounts but we have what's called signal amplification which means that tiny amount of hormone can have a huge effect okay so our hormones are very potent so our our circulating hormone concentrations can remain very relatively low but still have big effect and so you can see that here's here's what that enzyme amplification looks like small stimulus a tiny amount of hormone activates these um second messenger systems activates enzymes we get a lot of metabolic products so a lot of that protein or whatever that's going to cause that metabolic change and so we get a great effect we only need a teeny amount of hormone to turn on these Pathways as basically what's happening and so that's called signal amplification now when we talked about hormones we said that they have specificity and they have saturation one way that we can change sensitivity right one way we can AR alter Target cell sensitivity is to change the number of receptors so if we have a cell and we want to make it more sensitive we're going to increase the number of receptors higher chance that that hormone is going to bind to the receptor and cause a change and so that is called upregulation or the opposite we can reduce the number of receptors called down regulation it makes that cell less sensitive okay and we actually use up regulation and down regulation as part of our treatments as well so here you can see I don't know why I did a bad drawing when you've got these nice drawings right so up regulation increased number of receptors increases sensitivity and increases the response if we have too much of a response then we can actually initiate down regulation which is going to decrease the number of receptors and then it will decrease the response all right looking at hormone inter action so we have all of these hormones circulating through the blood they are reacting only at the Target organs and causing changes but we've already seen that these hormones can work together they can interact right so there are kind of three ways that they can interact if they're going to interact synergistic synergistic means that they're going to work together to have a greater effect we see this a lot in um like our reproductive system so like FSH and testosterone work together to boost sperm production okay or and I think this one's the trickiest one permissive effect where one hormone enhances the response to a second hormone but we do see this reproductive system in the female reproductive cycle between estrogen and progesterone and then the last one is antagonistic effects I think this one is the easiest um and this is when hormones have opposite effects so we see this with parathyroid hormone and calcitonin we see it with insulin and glycogen insulin and glucagon sorry insulin and glucagon Okay so so again insulin and glucagon insulin is going to lower blood glucose glycogen glucagon is going to convert glycogen to glucose and help increase blood glucose levels all right we said that the endocrine system is slower and one of the reasons that it's slower is it starts and stops slower we've seen that it starts slower partially because of we have to activate those metabolic pathways we have to go through through that transcription and translation to get genes converted to proteins and that just takes time well once we get those proteins in the blood we also or get the proteins and the hormones in the blood we also have to it will take time to remove them or filter them out right and so those hormone signals are taken up and so the hormones themselves are broken down by the liver and filtered out through the kidneys and that takes time and again remember that those steroid and thyroid hormones that are bound to the proteins in the blood the transport proteins in the blood are protected a little bit from this so hormone clearance or removal of the hormone from the blood is called metabolic clearance rate so essentially it is how fast or how slow are we able to remove that hormone from the blood and this is measured through halflife halflife is the time that it takes to get 50% of the hormone from the blood so if you start at 100% And you go to one half life then you have 50% and then you go two half lives 25% and then three half life so it's getting half each time 12 and a half half and then it's 6.25% etc etc okay so the halflife is how long it takes to take 50% of it so the faster right the faster the metabolic clearance rate a that means we have a shorter halflife so if the halflife is five minutes that's going to be cleared from the blood faster than a hormone that has a halflife of five hours okay so a shorter Half-Life means a faster metabolic clearance rate and a longer Half-Life means a longer metabolic clearance rate means that hormone is going to be present longer all right this section we want to specifically focus on stress and how the body responds to stress and the adaptations that we use for managing stress so what is stress stress is any situation that upsets our homeostasis it can be physiological it can be psychological regardless of what the stressful stimulus is our body body reacts to stress with a predictable stress response and it is called the General Adaptation Syndrome or gas um typically we're going to be looking at elevated levels of epinephrine and cortisol and it's going to occur in three stages so the first stage here is our alarm reaction so if you think alarm reaction I hope you're thinking your fight ORF flight so your sympathetic nervous system so primarily we're looking at elevated levels of epinephrine and norepinephrine from both the sympathetic nervous system and the Adrenal medulla this is going to prepare us for that fight ORF flight yes there's a stress can we get out of it right can we can we can we can we get out of it can we protect ourselves from it okay so we get that fight ORF flight response we're also going to be using up our glycogen because we are um using it to fuel our FF flight response right um we also will see increase in aldosterone and Angiotensin levels and this is to help increase our blood pressure to get blood to our skeletal muscles so we can fight or run away whatever we decide we need to do right so our second stage then is the stage of resistance um and this is after a few hours so if the stress continues okay we used our glycogen we used our quick energy now we've got to start thinking about alternative energy sources to maintain that fight ORF flight okay this is where cortisol is going to start to take over okay so we're going to get increased corticotropic release hormone from the hypothalamus increased act from the pituitary that's going to increase cortisol this is where we're going to start using fat and protein right fatty acids amino acids to try to make glucose because the glycogen is gone all right cortisol does have this glucose sparing effect so that it will inhibit protein Sy synthis so we're trying to use up our free amino acids instead of breaking down protein in our body protein is muscle okay um during this stage however because of the length of the stressor and excuse me trying to protect our body again right that increased cortisol over time does depress our immune function so that increas Ines our likelihood of getting an infection it's also why ulcers can be worsen during stress okay our lymphoid tissue atrophies further making us susceptible to infection right antibody levels drop wounds heal poorly okay so we have an increased risk of infection because of the decreased immune function which unfortunately could just further increase the stress that's occurring in our body right so the final stage of stress is the stage of exhaustion this is when the stress becomes so much that it overwhelms our homeostasis we're going to see rapid Decline and we could see death okay this is when the stressor has continued for several months this is why taking care of yourself is so important not just physically but mentally stressors can be physical or mental stressors at this point after several months glycogen is gone fat is gone we cannot maintain homeostasis the only source we have for glucose at this point now is protein protein is muscle we're breaking down muscle we're causing muscle wasting and atrophy okay we can't maintain glucose levels okay we get water retention um it's going to cause us to have hypertension okay this is going to this uh retaining of water and hypertension increase blood pressure okay it's going to it can it could throw off our electrolytes as well okay so that we end up with low potassium that can change change our pH okay this can lead to death if we don't stop the stressor we can have death from heart kidney failure or that overwhelming infection because of that immune suppression all right please take care of yourself all right the last thing that we need to talk about for the endocrine system are eosino and other signaling molecules so these we're looking at primarily the paracrine and autocrine so these are more of those local hormones specifically so u a paracrine will'll go a short distance so some examples are histamine nitric oxide catacol amine okay autocan Auto self okay so it's going to stimulate the same cell um heidin which is from the liver is an example of that okay and again similar to our nervous system where we can have the same chemicals act as a neurotransmitter or a hormone the same chemicals can be a hormone a paracrine a neurotransmitter it just kind of depends on where it is being released from so I want to look at the eosino specifically um because it's an important paracrine secretion for pain and we actually utilize a lot of our pain medications we'll utilize this p pathway and so I want us to look at that okay um and so we have several enzymes here and um different molecules that signal pain so our eosino are Divi derived from arachidonic Acid lipooxygenase so this is where it's going to start from radonic Acid Li lipo oxygen is an enzyme okay it will convert that to lucot triin lucot triin are chemical signals that are involved in allergic and inflammatory reaction now another part of the pathway is that um a different enzyme cyc oxygenase can convert arachadonic acid into either prosty thromboxanes or PR glands prostacyclin will inhibit blood clotting and Vaso constriction thromb boxin is opposite of that right it will stimulate baso constriction and blood cling and then prostaglandins have a whole bunch of different roles there's a whole bunch of different types of prag glanded okay um and so they do a lot of different things but I want you to see that we use how how we use these for treating like inflammation and pain okay I kind of like this best because you can kind of see it okay so here's our phospholipase A2 enzyme okay converts to arachadonic acid arachadonic acid then can by lipooxygenase can be converted to lucrin or cyc oxygenase can convert arachadonic acid to prostacyclin THB boxin and prostaglandins so here's what I want you to focus on cortisol and our steroid anti-inflammatory drugs block phospholipase A2 this is an enzyme so it stops we don't even make arachadonic acid so it stops this entire pathway okay so we don't get lucot trines we don't get prostacyclin we don't get thoin we don't get prag okay so cortisol and our steroid anti-inflammatory drugs do that now on the other hand our ineds are non-steroid anti-inflammatory drugs okay they block cyc oxygenase and so they will block the production of prostacyclin thoin and prostaglandins only but we will still get lucot Trine production so so what does all this mean okay so our steroid anti-inflammatory drugs again are going to block that phospho lipos A2 enzyme so we don't even get arachadonic acid okay so it inhibits all of those eosino disadvantage is overuse of cortisol and steroid anti-inflammatory drugs can produce symptoms of symptoms of Cushing syndrome aspirin ibuprofen celibre these are nonsteroid anti-inflammatory drugs these are also called Cox inhibitors because they block the cyc oxygenase enzyme um these are useful in treatment of fever and thrombosis because they inhibit the prag glandon and the boxine synthesis without inhibiting the lucot Trine production all right so we've gone through all of the hormones we've gone through all the hormone action we talked briefly about the stress and eosino the very last section here is discussing specific endocrine disorders our endocrine disorders basically fall into one of two main categories the disorder is either a hypo secretion so hypo means low so this is a we're not producing enough of the hormone or it's a hypers secretion where we are producing too much of the hormone so for these disorders just know which hormone so you need to know is it a hypo or hypers secretion what hormone and then just kind of a general idea of the effect so diabetes insipidus is a hypo secretion of ADH okay the effect of this is we are unable to retain water therefore individuals with diabetes and citus will drink water and urinate and drink and urinate and drink and urinate so they have a lot of thirst um some examples of some hyp secretions uh theoc chromosoma is a excess it's a tumor in the Adrenal medulla so we get excessive epinephrine so the effect of that is we would have that constant kind of fight ORF flight jitteriness right um another example is a toxic goer or Graves disease in this case we have antibodies Auto antibodies so this is an autoimmune disorder Auto antibodies mimic TSH so the thyroid gland thinks that it's getting a signal from TSH to make thyroid hormones and so that causes a thyroid hyp secretion okay so let's look we're just going to start at the top again and let's go pituitary right um gigantism gigantism is a hypers secretion of growth hormone during childhood okay um the reason that it causes gigantism is it's before those Epi growth plates have closed right and so the growth plates are not depleted and so excess growth hormone causes excessive long bone growth pituitary dwarfism is a hypos secretion of DH during childhood okay again it would cause a decrease in stature because of a lack of growth hormone this one however is relatively rare now um because we do have synthetically made growth hormone gr or growth hormone that's genetically engineered by bacteria um and so we can actually replace any missing growth hormone with growth hormone third one you're probably not as familiar with acromegaly this is a hypers secretion of growth hormone during adulthood so instead of long bone growth the bones will thicken okay and so it thickens the bones and the soft tissue and so you can see here how it makes a difference in like the structure of the fingers right the fingers are much thicker because of that bone growth there are so many so many thyroid diseases okay so we're just going to talk about some of them um congenital hypothyroidism so congenital means from birth um hypo so love low thyroid hormone madmia is adult adulty adult hypothyroidism so this is when we have low hypothyroidism as an adult both tra both types can be treated with oral thyroid hormones um then we have an endemic goer so we had a toxic goer earlier which was a hyp secretion because of the auto antibodies that mimic TSH an endemic goer is a hypo secretion of thyroid hormone and it's because this is where that iodine comes in right it's because we have a lack of dietary iodine so because we lack the dietary iodine we can't make thyroid hormone so we get an increased in thyroid stimulating hormone it's like hey I told you to make more thyroid hormone and you didn't so I'm going to keep telling you to make more and you aren't and so the thyroid gland is going to enlarge and the colloid enlarges but there's no thyroid hormone in there okay and that causes that visible goer endemic goers are again relatively rare especially in the US we have iodized our salt so we have added iodide to our salt so that we get enough iodine in our diet um we can also have parathyroid diseases hypoparathyroidism is low um par parathyroid hormone secretion um usually this only happens if the parathyroid glands are removed during thyroid surgery um but it can cause a decline in blood calcium levels and it can be fatal um because because it can cause spasms um in the Linex so people who have thyroid surgery are often monitored closely um to make sure that their blood calcium levels are maintained post surgery we can also have hyperparathyroidism typically caused by a tumor um it's going to cause our bones to become soft and fragile because we're going to increase that calcium into the blood adrenal dis disorders Cushing syndrome we said that one effect of overuse of the steroid anti-inflammatory drugs is that it could CA Cushing syndrome Cushing syndrome is when there's excess cortisol um it can cause hypoglycemia hypertension weakness swelling um we get muscle and bone loss um two telltale signs of Cushing syndrome is a moon phase so you get a rounded phase and buffalo hump which is when you get fat deposit on the back like around the neck adrenogenital syndrome or AGS is often accompanied by Cushing syndrome because again cortisol and the adrenal or and androgen um are secreted from the same areas of the adrenal cortex um and that can cause enlargement of um external sexual organs early on set puberty and could cause Mac masculinization of genitalia in women and girls so here's Cushing syndrome and so you can kind of see more of that that moon face and then here's adrenogenital syndrome to get masculinization okay probably the one you're most familiar with and I've been waiting all lecture for me to talk about is diabetes and mtis remember we did talk about diabetes in CPUs which is a hyposecretion of ADH diabetes malius is um the when we say diabetes what people are talking about is diabetes militis that has to do with blood sugar classic signs of diabetes militis polyurea polydipsia and polyphasia so excessive urine output excessive thirst and excessive hunger all right um people with diabetes mtis have hypoglycemia glucose in the urine ketones in the urine all right um and what happens here is because of the elevated blood glucose due to a lack or inactivity of insulin blood glucose is high okay when the kidneys filter it out they will reabsorb as as much of the glucose as possible but receptors have saturation that's called the transport Max so some of the glucose stays in the urine kidneys aren't able to reabsorb all that water so excuse me you have increased urine output because the glucose stays in the urine we're not able to absorb that water it's also how you end up with glucose and the urine which you're testing somebody with diabetes metis right is because normally any glucose that's left in your blood is going to be fully reabsorbed by the kidneys but because of the excess blood glucose level it cannot be fully reabsorb so our diabetes malius we have different types um used to be typed based off of onset um now that is no longer the case um so type 1 diabetes is 5 to 10% cases in the US this is genetic so typically these people will present with diabetes malius at a younger age okay um the insulin level here is very low okay um and so they may not be producing insulin so it's got to be treated with insulin so they may have injections a pump an insulin inhaler and they've got to Monitor and regulate their blood glucose levels type two diabetes is the one that is most common use typically historically had a later onset of diagnosis because it is actually an insulin resistance so the target cells are not as responsive to insulin as they should be so risk factors here there's a genetic component age obesity ethnicity okay typically type two diabetes is going to try to be treated with weight loss and exercise um because we are producing insulin we're just trying to increase the insulin sensitivity so loss of muscle mass causes difficulty with glycemia fat adapost tissues interfere with glucose uptake so if we can lose weight we can reduce adapost tissue that can help um also we can use glycemia lowering medications if not enough then they can use insulin as well so what's kind of the big deal about diabetes um so what happens is our cells can't absorb glucose have to use fat and proteins for energy so you may see weight weight loss and weakness um when we break down fat for energy it produces free fatty acids and ketones those are acidic that can cause our blood to become acidic okay it can cause keto acidosis um which is where those ketones are going to build up enough that it actually causes our blood pH to become acidic and that can send us into diabetic keto acidosis a person may be um hyperventilating it's called kousol respiration they're trying to blow off some of that acid um and then if they get that severe it's not uncommon for them to slip into diabetic Comas that become terminal okay um chronic pathology uh diabetes mtis can lead to neuropathy and cardiovascular damage um we get atherosclerosis microvascular disease arterial damage in the retina and the kidneys heart failure diabetic neuropathy because of the lack of um glucose it reduces blood flow um we get poor wound healing we lose sensation to that area um so it really is best for people with diabetes mtis long term we really want them to maintain that blood glucose level and monitor it um and try to keep it within that normal range and maintain it within that normal range as much as possible that helps reduce some of this chronic pathology and the likelihood of the um you know neuropathy and cardiovascular damage all right and that is it for the endocrine [Music] system