0:00 In this video, we're going to look at the otonomic nervous system. 0:21 The otonomic nervous system can be divided into the sympathetic nervous system, 0:25 also known 0:25 as the fight to flight response and the parasympathetic nervous system, also 0:29 known as the rest and 0:31 digest response. 0:33 The otonomic nervous system is involuntary control of body tissues. 0:37 It arises from the central nervous system, which is our brain and spinal cord 0:42 basically. 0:44 So here I am drawing the brain and the spinal cord. 0:47 The spinal cord can be divided into segments. 0:50 The spinal cord is divided into thirty-one, thirty-one sort of segments. 0:59 We have eight survival, twelve thoracic, five lumba, five sacral, and one coccy 1:05 geal segments. 1:08 These are important because the sympathetic and parasympathetic nerves arise 1:15 from these 1:16 spinal cord segments. 1:18 Remember that the otonomic nervous system is involuntary and that we have no 1:23 control over 1:23 it. 1:25 Now let us look at the purpose and function of the sympathetic and parasymp 1:29 athetic nervous 1:30 system and how they differ from each other. 1:35 So the sympathetic nervous system, for example, prepares for activity. 1:39 It provides more glucose so you can have energy. 1:42 It increases the heart rate, dilates the pupils, and prevents the activity of 1:50 digestion. 1:51 The parasympathetic is the rest and digest response on the other hand. 1:55 And its main goal is to conserve body energy. 1:58 So these include increasing gut mobility, stimulate digestive secretions, and 2:05 slow down 2:05 heart rate, amongst many other things. 2:10 Now let us mainly focus on the sympathetic nervous system, so the fight or 2:15 flight response. 2:16 Now let us look at what organs the sympathetic nerves mainly target, just 2:23 overview, and what 2:24 they do. 2:26 But first I must introduce the ganglions here. 2:30 The ganglion is where nerve cells synapse with one another. 2:34 So usually in the sympathetic and parasympathetic nervous system, especially in 2:39 the sympathetic 2:40 nervous system, there are cells coming out of the spinal cord and then they syn 2:45 apse in 2:45 the ganglion and then this new cell will then target the tissue. 2:51 So there are many sympathetic ganglions but here I am only drawing the 2:55 sympathetic chain, 2:57 the celiac and the inferior mesenteric ganglions which supply the abdominal 3:04 area of our body. 3:06 Another very important thing to understand about the sympathetic nervous system 3:10 is the 3:11 nerves arising from the spinal cord. 3:15 They arise from the thoracic and lumbar regions of the spinal cord. 3:21 Anyways, so here we can see some pre-ganglionic neurons coming from the spinal 3:29 cord and then 3:30 they will synapse in the ganglion here. 3:34 And then this new neuron is called the post-ganglionic neuron, which will then 3:39 carry the sympathetic 3:40 information to a target tissue. 3:42 Again, we won't go into too much detail into the nerves and where they come 3:47 from essentially. 3:48 Just know that the sympathetic nerves originate either from the thoracic or l 3:53 umbar regions 3:54 of the spinal cord. 3:57 So sympathetic activity will target the pupils, for example, causing the pupils 4:01 to dilate 4:02 for greater vision. 4:04 It will also target the salivary glands, inhibiting salvation. 4:10 Sympathetic activity will relax your airways and increase the heart rate and 4:15 this is normal 4:16 during activity. 4:20 Pre-ganglionic neurons that will target the abdominal cavity will synapse in 4:26 the celiac 4:27 ganglion. 4:28 And these post-ganglionic neurons will then target the digestive organs to 4:33 inhibit digestion. 4:35 It will target the liver to stimulate glucose production. 4:44 And then neurons arising from the lumbar segment of the spinal cord will target 4:49 the adrenal 4:50 glands and will stimulate adrenaline and noradrenaline production. 4:56 And this will promote sympathetic activity. 5:00 Then we have post-ganglionic neurons from the inferior mesenteric ganglion that 5:04 will 5:05 target the bladder causing it to relax, so inhibiting micturition, as well as 5:10 targeting 5:11 the genitals to stimulate orgasm. 5:14 Okay, so that was for the sympathetic activity and the purpose of the 5:18 sympathetic activity 5:20 is to prepare the person for exercise, basically, you know, such as running or 5:25 playing some 5:25 sports or running away from a lion. 5:32 Looking at the parasympathetic now, it's all to do with resting and digesting. 5:37 So this is essentially, this parasympathetic activity essentially is what 5:42 occurs after 5:42 we eat and we're just resting, lying down. 5:46 For the parasympathetic nervous system, we have to introduce the brainstem 5:50 because the 5:50 parasympathetic nerves, a lot of parasympathetic nerves arise from the brain 5:56 stem, as well as 5:57 the sacral region of the spinal cord. 6:01 So cranial nerve three causes pupils to constrict. 6:07 This is part of the parasympathetic nervous system. 6:10 Cranial nerve seven, the facial nerve stimulates salvation by targeting the sal 6:16 ivary glands. 6:17 Similarly, cranial nerve nine also targets the salivary glands to stimulate 6:23 salvation. 6:25 A very, very important nerve, which is probably the main parasympathetic nerve, 6:30 is the cranial 6:31 nerve number 10, which is also known as the vagus nerve. 6:35 The vagus nerve literally targets most of the organs and tissues for parasymp 6:41 athetic 6:42 activity. 6:44 So it causes constriction of the airways, slowing the heart rate down. 6:50 It stimulates digestion and dilates intestinal blood flow. 6:58 So we should have said this, but the parasympathetic neurons, they arise from 7:04 either the brainstem 7:06 or the sacral region of the spinal cord. 7:09 So this nerves arising from the sacral region will target the rectum, causing 7:14 it to relax. 7:15 And also there are nerves that will target the bladder, causing bladders to 7:20 constrict. 7:21 So initiating micturition, peeing, as well as we have nerves that will target 7:27 the genitals 7:28 from the sacral segment. 7:30 When the parasympathetic activity targets the genitals, it will actually 7:33 stimulate arousal. 7:35 So for example, the parasympathetic nervous system is responsible for 7:39 maintaining an erection, 7:41 whereas the sympathetic will cause ejaculation, so orgasm. 7:47 So that was for the parasympathetic nervous system, whose main function is for 7:52 rest and 7:53 digest. 7:55 Now let us look into the synapses and neurotransmitters involved in sympathetic 8:00 and parasympathetic 8:02 activity. 8:03 So let's take a section of the spinal cord and see how information from the 8:08 central nervous 8:09 system, so from the brain and the spinal cord, travels to the tissues via the 8:15 parasympathetic 8:16 or sympathetic nerves. 8:20 Let us first look at the parasympathetic neurons and neurotransmitters. 8:25 Information from the central nervous system comes down and it will transfer 8:30 this information 8:31 to a pre-ganglionic neuron, which in the parasympathetic nervous systems case 8:38 is a lightly 8:39 myelinated neuron, which is quite long. 8:45 The pre-ganglionic neuron will release neurotransmitters, acylcholine, which 8:50 will transfer this 8:52 essentially propagation of information to the post-ganglionic neuron, which is 8:57 often 8:57 unmyelinated and quite short. 9:04 And then this unmyelinated post-ganglionic neuron, which is quite short, will 9:09 release 9:10 a neurotransmit acylcholine again, which will target a tissue, causing a parasy 9:14 mpathetic 9:15 response. 9:16 Now in this case, it's targeting the heart, so it will release acylcholine to 9:22 slow down 9:22 the heart rate. 9:23 But this image is not quite correct because there is no ganglion when the par 9:30 asympathetic 9:31 nervous system targets the heart, but I hope you just understand the concept 9:36 and the difference 9:37 between the parasympathetic and sympathetic anyway. 9:42 So now let's look at the sympathetic. 9:44 Now in the sympathetic, we also have a ganglion. 9:47 Information from the central nervous system will essentially send information 9:52 to the pre-ganglionic 9:54 sympathetic neuron, which in this case is lightly myelinated and quite short. 10:00 It will synapse in the ganglion, release the neurotransmit acylcholine, so you 10:05 can see 10:06 some similarities now between the sympathetic and parasympathetic, there's acyl 10:10 choline. 10:11 Now this new post-ganglionic sympathetic neuron is actually going to be unmyel 10:16 inated and long. 10:19 And this post-ganglionic neuron will release noradrenaline, the neurotransmit 10:25 ant noradrenaline, 10:27 to target the heart and to increase the heart rate. 10:31 So if you look at this diagram, you can see some differences in pre-ganglionic 10:35 and post-ganglionic 10:36 neurons of the sympathetic and parasympathetic nervous system. 10:40 You know, one is short, one is long, and it's opposite for both nervous systems 10:47 . 10:48 Anyways, when dealing with the sympathetic nervous system, it's important to 10:51 introduce 10:52 another tissue. 10:54 So if here the information is in the pre-ganglionic neuron, it's carrying the 10:59 sympathetic information, 11:01 it's short, it's lightly myelinated. 11:03 This neuron can target the adrenal glands, releasing acylcholine, which will 11:09 target the 11:09 adrenal glands, specifically the adrenal medulla. 11:12 It will stimulate the adrenal medulla to produce noradrenaline again. 11:18 So noradrenaline can be stimulated from the adrenal glands by the sympathetic 11:23 nervous 11:24 system, or it can be also produced by some, or by the post-ganglionic 11:28 sympathetic nerves. 11:30 And both these noradrenaline, regardless of where they come from, when they 11:35 target the 11:35 heart, they will increase the heart rate. 11:38 And this is what you want when you're exercising, increasing heart rate. 11:42 So I hope that made sense. 11:43 I hope you enjoyed this video. 11:44 It was an introduction to the sympathetic and parasympathetic nervous systems, 11:48 which 11:48 are part of the autonomic. 11:50 Thank you.
