Overview of the Endocrine System

Hello everyone, Dr. Mike, here in this video we are going to take a look at the

endocrine

system

. Now the

endocrine

system

is a set of cells and glands that produce and release hormones. These hormones are just chemicals that jump into the bloodstream and have their effect. In distant areas of the body there is now a communication network similar to the nervous system that controls physiological activity, but it is a little different, it is different in the sense that the nervous system is very fast, it is very direct and generally has a short action . The endocrine system is the opposite, its effect is quite slow, it is not direct because it jumps into the bloodstream and travels to very distant areas of the body and can last a long time.

Some hormones when released can have long-lasting effects. From hours to days and sometimes weeks, so in this video we'll go over some of the important cells or glands that produce and release hormones, discuss what these hormones are, and take a quick look at their activity or function in the body. We're going to do this, a top down mechanism, start at the top and work our way down, so to begin we need to start in the brain, specifically at the base of the brain, there's something called the hypothalamus that tells you what's underneath. of the thalamus, this is the hypothalamus, it is located here, we have taken it here, here is the hypothalamus and you can see that there is an extension of the hypothalamus that has two lobes or two parts, this is called the pituitary gland and that is another endocrine tissue or gland that itself produces and releases hormones, the hypothalamus produces another series of hormones that have the effect of controlling and regulating the endocrine system of many other tissues in the body, which is why we now call the hypothalamus the master regulator or control center of the endocrine system. five important hormones that the hypothalamus produces and releases to control many other aspects of the endocrine system.

These hormones are thyrotropin-releasing hormone, corticotropin-releasing hormone, growth-releasing hormone, prolactin-releasing hormone, and gonadotropin-releasing hormone, so a couple of points here, releasing hormone, tells you how it works. elsewhere release a hormone, it also makes sense tropon as a suffix tropine at the end of the word, if you see a hormone with tropon as a suffix, it means that it will go to another tissue in the body to tell it to release. another hormone, okay, so how does this work? The hypothalamus communicates with both the posterior and anterior aspects of the pituitary gland, but interestingly, the anterior part is connected to the hypothalamus via a blood supply, meaning the only way the hypothalamus can communicate with it is It is liberating. hormones and travel through this blood supply to tell the anterior pituitary gland to release its hormones.

The posterior pituitary gland is connected to the hypothalamus via nerves, which means that the hypothalamus does not need to release hormones to tell the posterior gland to do so, it simply sends a nerve signal downward to tell the posterior to release hormones. Well, these hormones that are named here that are produced by the hypothalamus move through the blood supply to the anterior pituitary to tell the anterior pituitary to release a number one hormone, the hormone that is told What is released from the anterior pituitary gland is thyroid-stimulating hormone, the second hormone. Now there is no particular order.

I'm just arranging it here basically for ease, but there's no particular order, but the second hormone that's released is the adrenocortical tropic hormone. The third is growth. The fourth hormone is prolactin and the fifth is gonadotropin. Gonadotropins and there are two gonadotropins that you need to know: luteinizing hormone and follicle-stimulating hormone. Well, what's going on? Thyrotropin-releasing hormone released by the hypothalamus stimulates the release of thyroid-stimulating hormone. This is a hormone that now jumps into the bloodstream and goes to the thyroid to tell it to release its hormone, so let's look at this number one that tells you that one to be released and jumps into the bloodstream goes to the thyroid, so let's take a look at the thyroid quickly the thyroid is endocrine tissue that hugs the front of the trachea the trachea what you will find is that the thyroid produces a couple of important hormones: it produces t3, which is also known as triiodothyronine and t4, which is known as thyroxine.

Interestingly, T4, well, most of it is converted to T3. T3 is the most active thyroid hormone, so when we talk about thyroid hormones, we talk about T3 predominantly, 80 percent. 20. That's the ratio we see here. There is another hormone that the thyroid releases called calcitonin calcitonin talks about that in a second so that the thyrotropin releasing hormones released by the hypothalamus travel through this blood supply it tells the anterior pituitary to release the thyroid stimulating hormone that jumps to the bloodstream tells the thyroid to release t3 and t4 what do they do? extremely important role in the development of metabolism and the release of catecholamines what are catecholamines catecholamines are neurotransmitters these are things and hormones are things like adrenaline or norepinephrine or epinephrine norepinephrine for example that is what thyroid hormones do calcitonin is interestingly what calcitonin does is it decreases the amount of calcium in the bloodstream if there is too much calcium in the bloodstream calcitonin decreases that calcium helps us reabsorb and retain that calcium predominantly in our bone tissue which is the hormone thyroid, which happens when corticotropin-releasing hormone is released from the hypothalamus and travels through this blood supply, stimulates adrenocorticotropia. hormone to be released, also known as acth, which jumps into the bloodstream and travels to the adrenal gland, adrenal cortex, adrenal cortex, the outside of the adrenal gland, the tropics tell it to release another hormone, so everything is in the name, let's go to the adrenal gland now.

Adrenal gland now, if we look at the adrenal gland, we have the cortex, which is the outside, like its shell, and we have the medulla, which is the inside, where different hormones are released, for example, the adrenocorticotropic hormone will go to the cortex more specifically and it will release cortisol and it will release aldosterone and androgens. We'll leave out androgens, but androgens, which are male sex hormones, so cortisol, what does cortisol do? Does cortisol increase blood glucose? Cortisol also suppresses the immune system and cortisol also stimulates our fight or flight response really important what does aldosterone do?

Does aldosterone increase our salt reabsorption? What does that mean? increases our salt reabsorption. Aldosterone travels to our kidneys and tells our kidneys not to urinate because salt or sodium keeps it in the blood. This is important. because wherever sodium goes water follows, so if we reabsorb more sodium into our bloodstream, water follows and our blood volume increases, which means our blood pressure increases, aldosterone helps increase blood pressure, increases blood volume and also maintains hydration. It is very important, what happens to the marrow? The medulla is not stimulated very strongly by acth, but the hormones that are released inside the adrenal gland are predominantly noradrenaline and adrenaline, what are they?

Is that norepinephrine and epinephrine? What else? growth hormone. Well, the growth hormone is released from the anterior part. pituitary gland and that stimulates growth, as you would expect, growth hormone stimulates growth, increases growth, things like increased protein synthesis, for example, increases growth, increases metabolic processes, okay, prolactin, prolactin, lactin, lactation, breast milk production, prolactin, then, prolactin which is released by the anterior pituitary gland in response to prolactin-releasing hormone from the hypothalamus which stimulates milk production increases milk production now It is not the milk ejection that decreases through breastfeeding, that is the oxytocin which I will talk about in a second and then the gonadotropins, the gonadotropins, so the tropon goes to the gonad so for women the ovaries for For men, the testicles and these hormones go to both of them.

For women, they go to the ovaries. For men, they go to the testicles and it has its function. What is its function? Well, luteinizing hormone. Let's first look at the ovaries. What luteinizing hormone does is stimulate progesterone. , it also stimulates ovulation, ovulation and progesterone, follicle stimulating hormone stimulates follicle maturation, what does that mean? In the female reproductive cycle, you have these immature primordial follicles that eventually develop into an oocyte or ovum that is released for the fish. Released by the hypothalamus, specifically the anterior pituitary gland stimulates these follicles to begin moving through the process to progress toward the release of a mature egg.

The actual release from the egg is luteinizing hormone, so the maturation of the follicle also leads to the production of estrogen, so two really important hormones that are released here in response to LH are progesterone and fish estrogen. . What happens in the testicles? Let's take a look at the males in the testicles. Luteinizing hormone stimulates a certain type of cells called latex cells and what they produce is testosterone, which is the hormone produced here. What about follicle stimulating hormone? Well, there are no follicles in men, but what it does is it stimulates a certain type of cells in the testicles called setoli cells, so both women and setoli cells are in the testicles.

Women produce testosterone, so she produces something called androgen-binding protein. and they both come together to promote sperm production, so as you would expect, the ovaries, luteinizing hormone, follicle stimulating hormone, produced hormones here and what this does is it leads to the preparation of the uterus, so so if you are preparing the uterus and producing sperm, both things come together. It is going to support the reproduction that happens through the anterior hormones. What about those are the hormones of the posterior pituitary? There are only two you need to know here there are oxytocin and an antidiuretic hormone known as adh also known as vasopressin.

Okay, first of all, the hypothalamus doesn't produce any hormones to travel down to tell them to release it's just a nerve signal, in fact the hypothalamus produces these two hormones and sends them down and they just get stored in the pituitary gland. later. Now what oxytocin does is we know it's an important building hormone. relationships, but it also tells the smooth muscle to contract, it tells the uterus to contract, and it tells the smooth muscle of the breast to contract to expel milk, so uterine contractions and milk ejection, in addition of building both positive and negative relationships, it is not that hormone that makes us feel good.

Everyone says that antidiuretic hormone diuresis means releasing urine to release fluid from the body. It is antidiuresis, so it stops the release of that fluid, so you stop urinating, so this hormone is released in times of dehydration. If we need to maintain the water we release. this hormone travels to the kidneys and the kidneys hold water and we don't urinate it, so it stops urination, it's there to maintain hydration, so that's the hypothalamus, the pituitary gland, we've gone through the adrenal glands, too and We have reviewed sex hormones and the thyroid, there is a hormone or should I say there is a gland that is located behind the thyroid called the parathyroid gland and what is the parathyroid gland releases parathyroid hormone and opposes the activity of calcitonin, so calcitonin decreases. calcium parathyroid hormone increases calcium in the blood, so if our calcium is too low, the parathyroid releases parathyroid hormone, calcium jumps if calcium is too high, calcitonin is released and decreases calcium levels.

Can you see that what is happening here is that the endocrine system maintains homeostasis and keeps the body functioning brilliantly? that is the parathyroid hormone the kidneys also release some hormones renin, for example, and erythropoietin what renin does is that it works together with aldosterone increases blood pressure increases blood volume erythropoietin increases the production of red blood cells why do Would the kidneys control the production of red blood cells well? because the kidneys need to keep being fed with oxygen because it is a very hungry tissue, so the production of red blood cells the pancreas we cannot forget about the pancreas the pancreas is both an endocrine and exocrine tissue exocrine means that it produces chemicals that are released in Ducts, these ducts are contained and this is part of the digestive system, soIt releases digestive enzymes but also releases hormones.

Two really important hormones are insulin and glucagon and again, these are opposite hormones, so insulin lowers blood glucose levels when they are high. glucose Glucagon increases blood glucose levels after a meal. The released insulin draws glucose into the cells to use for energy if we are not eating and four to six eight hours have passed and we have not eaten. The release of glucagon and it releases stored glucose into the bloodstream and then the cells can use it for energy, so what we've seen here is a relatively quick tour of an

overview

of the endocrine system.