 Hi everyone, this is Leah, your lead course instructor here at ACT and we are going to continue on with our anatomy and physiology lesson. And today we're going to talk about the endocrine system. So here's an overview of the endocrine system. The endocrine system is a network of glands and organs located throughout the body. We all play a vital role in controlling and regulating many of our bodies functions by way of chemical messengers called hormones. So these hormones are secreted by these different glands within the endocrine system and they travel throughout the bloodstream to various organs and tissues in the body. And these hormones then instruct or tell these organs and tissues what to do or how to function. So functions here of the endocrine system, one is water equilibrium, so the endocrine system controls water equilibrium by regulating the solute concentration of the blood. Also the endocrine system is responsible for the growth, metabolism and tissue maturation. So it helps to control many of the tissues like the bone and muscle and the degree of metabolism of various tissues, which helps in the maintenance of the normal of a normal body temperature and normal mental functions. We also have heart rate and blood pressure management. So the endocrine system is very important here in assisting and managing heart rate and blood pressure and helps in preparing the body for a physical motion. The endocrine system also is helpful and responsible for the immune system control. So by helping to regulate the production and functions of immune cells. And then also reproductive function controls that we just went over the reproductive system. And so we talked a little bit about that in that last lesson, but the endocrine system helps to regulate the development and the function of the reproductive systems in both males and females. So continuing on with functions of the endocrine system. There are a lot of endocrine system is very important and vital as you can see here. So uterine contractions and milk release, the endocrine system helps throughout the delivery of a newborn and stimulates milk release in females that are breastfeeding, island management. So also helps to regulate sodium, potassium concentrations in the blood. And then it also helps with blood glucose. So and the endocrine system controls blood glucose levels and other nutrient levels in the body. And then there's also responsible for direct gene activation as well as a second messenger system as you can see here. So organs of the endocrine system, as I said, there are glands of the endocrine system where these hormones are produced, stored and released. And each gland produces one or more hormones which go on to target specific organs and tissues as we talked about. Some of these glands and organs include the pituitary, the thyroid, the parathyroid, the adrenal, the penile, the thymus, the pancreas and the gonads. It's also important to note that the hypothalamus of the brain, though part of the nervous system is also considered as a major endocrine organ because it produces several hormones. So it is an important autonomic nervous system, an endocrine control center of the brain. So I just wanted to make a note of that here. So first we'll start with the pituitary gland. So the pituitary gland is located behind the hypothalamus. It is approximately the size of a pea. It has two functional lobes, the anterior pituitary and then the posterior pituitary. And you can see here is the brain and then the pituitary gland is right here. So there are different hormones that both the anterior and then the posterior pituitary gland produce. I'm not going to read all of these down here through the anterior pituitary list because you can read them, but you can see the anterior pituitary gland produces growth hormone, prolactin, thyroid stimulating hormone, also the FSH, which we talked about in our reproductive lesson, the follicle stimulating hormone, and then the luteinizing hormone as well. And then of course the hormones of the gonads. And then the hormones of the pituitary gland, oxytocin, is of course helps, is released during childbirth and in nursing women. And then the antidiuretic hormone helps to cause the kidneys to reabsorb water from forming a urine. The thyroid gland, as you can see, is right here. It's in the front part of your neck. It's very important for metabolism. So the thyroid hormone controls the rate of which glucose is burned and converted to body heat. So it's also important for normal tissue growth and development. And the thyroid produces thyroxine or T4 and thyroining or T3. Here we have the parathyroid. So the parathyroids are actually located within the larger thyroid gland. So this is helpful and important for maintaining control of calcium levels in the bones and the blood. And it helps to secrete the parathyroid, secretes the parathyroid hormone, which is an important regulator of calcium of the blood. Here we have the adrenal glands. So one adrenal gland can be found on top of each kidney right here and right here, one on the right and then one on the left. And these glands produce hormones that are important for regulating functions such as blood pressure, heart rate, and your stress response. Here are the hormones of the adrenal glands. So there's the adrenal cortex and the adrenal medulla. And the adrenal cortex helps to produce the mineral corticoids and renin. And also the atrial natriuretic peptide, glucocorticoids, and the sex hormones. And then the hormones of the adrenal medulla produced are the catecholines. And the function of catecholines help to increase heart rate, blood pressure, blood glucose levels, and help to dilate the small passageways of the lungs. So moving on to the pancreas. So the pancreas is right here in your abdomen behind your stomach, and it helps to control blood sugar levels. The islets of Langhorn's also called the pancreatic islets are masses of hormone producing tissues scattered throughout the pancreas. Two important hormones produced by these cells are insulin and glucogen. Islet cells secrete insulin and glucogen during feeding and fasting times. The beta cells are high levels of glucose in the blood, stimulate the release of insulin from the beta cells. And then you have the alpha cells. And then glucogens released by the alpha cells is stimulated by low blood glucose levels. And then you have insulin, and we all know that insulin acts on the body cells and increases their ability to transport glucose across the plasma membranes. And then we have the glucogen as well. Moving on here to the penal glands. So this is also called the penal body. And it's a small cone shaped gland, as you can see here is the brain. And it hangs from the roof of the third ventricle of the brain. And so the penal gland is very important because it secretes melatonin. And that's the only hormone that the penal gland stimulates or produces. And the levels of melatonin rise and fall during the course of the day and night. So peak levels occur at night and make you drowsy as melatonin is widely known and believed to be the sleep trigger. And so it plays a very important role in establishing the body's wake and sleep cycle and day and night cycle. Here we have the thymus gland, as you can see that's right here. So the thymus gland is large in infants and children and decreases in size throughout adulthood. And the thymus gland produces a hormone called thymocin that is essential for the normal development of white blood cells or the T lymphocytes or T cells, which we also discuss in our immune lesson. So this obviously helps with the immune response. And then the endocrine system here again, the gonads, which we talked a lot about in our last lesson, but the female and male gonads produce sex hormones that are identical to those produced by the adrenal cortex. Hormones of the ovaries include estrogen and progesterone. And then hormones of the testes include testosterone. So chemistry of hormones. So the key to the power of the endocrine gland is obviously the hormones that they produce and secrete. So as we've been discussing hormones or those chemical substances that are secreted by these endocrine glands and to help to regulate metabolic activity of other cells in the body. So there's different classifications of these hormones, but nearly all of them can be classified chemically as either amino acid-based molecules or steroids. Steroid hormones include the sex hormones made by the gonads and hormones produced by the adrenal cortex. And then amino acid-based hormones are other non-steroidal amino acid derivatives. So here this was important for me to share with you is the control of the hormone release. So what prompts the endocrine glands to release or not release their hormones? Well, there's something called negative feedback mechanisms are the main ways of regulating blood levels of nearly all hormones. And the endocrine gland stimuli that activate the endocrine organs and it falls into three main categories. So hormonal, humoral and neural. So the hormonal stimuli is the most common and it is the endocrine organs that are prodded into action by other hormones. So the hypothalamic hormone stimulates the anterior pituitary gland to secrete its hormones and many anterior pituitary hormones then stimulate other endocrine organs to release their hormones into the blood. Then there's the humoral stimuli. So changing blood levels of certain ions and nutrients may also stimulate hormone release. In this, an example would be the release of parathyroid hormone by cells of the parathyroid gland is then prompted by the decreasing blood calcium levels. And then there is the neural stimuli. So in isolated cases, nerve fibers can stimulate hormone release and the target cells are said to respond to these neural stimuli. So an example would be the sympathetic nervous system stimulating the adrenal medulla to release neural epinephrine and epinephrine during periods of stress. So as we can see here, the endocrine system is I think very actually quite fascinating and interesting but also can be a little bit complicated. So if you again have questions or you need clarification about anything, you know that you can always outreach me by sending me an email or you could also schedule office hours with me. But thanks for listening and we'll be back again soon.