Hank tries not to stress you out too much as he delves into the functions and terminology of your sympathetic nervous system.
Going on, you start to feel it. those smoke heart starts to race, your breathing picks you are stressed. and i’m not talking about talking about the i’m-afraid-i-might-die kind of stress. actually very useful if you’re, y’know, trying to get out of a burning building. and it does its job exceedingly well by focusing like, when you’re facing a life-or-death cashew
Cluster in your intestines, or producing that’s all stuff that you can deal with later, when you’re out of harm’s way. blast all of your energy to your brain and heart so, this is where i tell you that you’re and that it keeps you alive. and that you would probably die in x period of time if you didn’t have one. responses are triggered all the time, practically
I mean, worrying about paying your wireless — those things are terrible, but they will not kill you. so, if stress is, like, ruining your life, that should get to know how it works. because by learning about your sympathetic you may recall from our tour of the anatomy both your sympathetic and parasympathetic divisions, each neuron travels from its root in the spinal yes,
That is a verb as well — with another to an effector organ, where it synapses again sending more blood to your skeletal muscles, or making your heart pump faster. actually communicate with each other? and by and large, the stress response includes two kinds of chemicals, both of which i’m sure you’ve heard of. and like we talked about in our lesson about with each
Other — or their effector organs — across a synapse. there are at least 50 different hormones at work in your body right now, and they do everything i’m telling you all of this now, up front, 100% necessary for understanding how your sympathetic division ultimately works. those chemicals can be kind of hard to keep track of. totally opposite effects — depending on
Where it’s received in your body. system, and hormones are products of your either a neurotransmitter or a hormone — even so all of this can make understanding your your brain sends action potentials down your when the signals reach the synapses inside a neurotransmitter — called acetylcholine, known to its friends as ach. in addition to working in sympathetic ganglia
Peripheral nervous system and lots of your so when it comes to nervous communication, ach is really the coin of the realm. the premium currency. action potentials in several neurons on the that’s all it does, but it’s important. it’s basically a signal booster. this case, let’s say your leg muscles, which and at the end of that second, postganglionic neuron,
The fiber releases a different neurotransmitter. from postganglionic fibers in the sympathetic nervous system. so, the preganglionic fiber releases ach, boom. congrats. your life is on its way to being saved. there’s another alternative for getting the message out. set leaving the spinal cord that goes directly to your adrenal glands. end up in another neuron that
Triggers blood your adrenal medulla to release a flood of that rush through your bloodstream toward your heart, lungs, and other organs. yeah, i said the adrenal glands release norepinephrine as a hormone. sent the final signal to control blood flow to the leg muscle. on how it’s being used. if it’s being released we refer to a messenger chemical — no matter being
Secreted by a gland into the bloodstream even if it’s the same chemical. and to an as good as neurotransmitter norepinephrine. now, the ways in which a neurotransmitter-slash- hormone like norepinephrine works, is a good example nervous system. because it works by both stimulating so, in our house-burning scenario, the norepinephrine blood flow in some parts of your body
— Like flow in other places where it’s not urgently needed — like your guts. responses? well, it all depends on the particular kind in the case of norepinephrine, its effector all of your involuntary functions of hollow on the smooth muscle cells controlling some alpha receptors — when norepinephrine, or make those smooth muscle cells contract, thereby restricting
Blood flow. for epinephrine and norepinephrine, and when so it makes sense that the smooth muscle around muscles — which you’ll need to get out receptors. because you want those blood vessels and since running away is more important than to your stomach and intestines have lots of those areas, because that burrito can wait until you’re out of the house. but the thing
Is, all of these functions work after all, it wouldn’t do you much good blood to your muscles, where it’s needed. and the receptors on the corresponding effectors, so, the system works well. really well. sometimes, too well. since your body’s reaction tends to be a i mean, we’re talking about throwing parts that’s not something you want happening every morning.
Actually end up endangering your life in the long run, because your body’s stress response is so effective. part of your stress response — the part that’s like high blood pressure, digestive problems, so what your body needs to do is figure out that is where your sympathetic system’s more mellow and yeah, that’s what we’re gonna be talking about next time.
Response and how the signals in your sympathetic the neurotransmitters acetylcholine in the and you learned that other signals can go and you also learned that the same messenger on the receptors, with alpha receptors causing a big shoutout and thank you to our headmaster contribution on patreon helps keep crash course if you want to help us keep making great videos this
Episode of crash course was co-sponsored crash course is filmed in the doctor cheryl was written by kathleen yale, edited by blake jackson. our director and script supervisor sweeney, our sound designer is michael aranda, and the graphics team is thought café.
Transcribed from video
Sympathetic Nervous System: Crash Course Anatomy & Physiology #14 By CrashCourse