字幕表 動画を再生する 英語字幕をプリント - [Instructor] What you see in these pictures, this is a forward view of a transparent man or a semitransparent man, and this is a posterior, or back view of a semitransparent woman. But what these organs that are depicted, these organs secrete molecules into the bloodstream, and an organ that secretes things, these are called glands, and they secrete these molecules into the blood stream that regulate other parts of the body, things that might be quite far away from the organs, the glands that actually do the secretion. And so these molecules that regulate other parts of the body, these are called hormones. And the word hormone comes from Greek hormōn, which means to set in motion, so one way to think about it, these are molecules that set things in motion in other parts of the body, and this is really to regulate the body function. Now this entire system of glands is referred to as the endocrine system, endo- referring to fact that it's acting within the body, -crine originally comes from Greek word to sift or to differentiate something and it's a system of organs or I guess you could say glands that are secreting molecules, these hormones into the bloodstream to regulate the body. I'm not going to go in-depth in all of these endocrine glands but just to give you an appreciation of what they do and what these hormones are all about, we could list some of the more common ones that you might hear about. So for example, the thyroid gland produces thyroid hormone. This is a version of thyroid hormone. You see your carbons in the dark gray, your hydrogens in the white. You see your oxygens in the red, nitrogen in blue, and these big atoms right over here, these are iodine, and thyroid hormone plays an important role in your metabolism. In fact, if you have too much thyroid hormone, that's a disorder called hyperthyroidism, which would make your metabolism overactive. Likewise, if you have too little thyroid hormone, that's a disorder known as hypothyroidism, in which case your metabolism isn't active enough. You have hormones like adrenaline that are released by the adrenal glands, and that's where it gets the word adrenaline from. It's often known as epinephrine, and adrenaline, you might hear things like, "Hey, so and so is an adrenaline junkie," which means they really like a thrill, and adrenaline actually does play a role there. It's involved in the fight-or-flight response, where it'll increase your heart rate and increase blood flow to the muscles. And what's really interesting about all of these hormones is they have so many impacts on the body because they're released into the bloodstream and to different cells they might do different things. This right over here is a variation of estrogen, which is produced primarily in females in the ovaries, but it also exists in a male body and it's associated with a lot of female bodily function, but once again, not strictly female. Estrogen also exists in males. Similarly, you have testosterone, which is associated with male function but it also exists in females, and it's primarily produced in men in the testes. Thus the name testosterone, but it can also be produced by the adrenal glands. And women, it can be produced by the ovaries. But you could also have a molecule like insulin which you can see is much larger than the other hormones that we have looked at. It's produced in the pancreas and it plays a super-important role in how we process sugars and how we store fat and scientists are constantly discovering new roles for these various hormones. Insulin in particular you might associate with diabetes. People with Type 1 diabetes aren't able to produce enough insulin to take the sugar out of their blood stream, to have the cells absorb the sugar. Insulin will bind to the surface of a cell so that it will start taking in sugar from the blood stream. People with Type 2 diabetes, they have an insensitivity to insulin, so they might have to take extra insulin in order for their cells to take in the proper amount of sugar. But the big idea here is that the endocrine system, although it might not be as obvious, or it might not be as well known as something like say the nervous system, it plays a pivotal role in your body. It helps regulate your body. It helps keep it at the right temperature, the right blood pressure, your heart pumping at the right rate. One way to think about this is the notion of homeostasis, which is derived from similar and staying the same. So keeping your body at the right temperature regardless of what the temperature is outside or regardless of what your body is doing, there's a whole series of roles that these hormones, which are released by these endocrine glands actually do.