Nervous System-Autonomic Nervous System

追加: 2026-05-30

[00:00:00]We are going to learn about the autonomic nervous  system today so just to recap what we have learned earlier let's review the entire nervous system  before we end the lecture with the autonomic nervous system so this we have done this slide  many many times I'm going to give you it again so there are several sensory receptors that  come from skin that come from your tongue there are receptors on the skeletal muscle there are  receptors on your reproductive digestive systems all these receptors various kinds of receptors  that that are called sensory receptors fast through the peripheral nervous system which is the  spinal nerves and the cranial nerves considered to be the peripheral nervous system take information  through the afferent root sensory information to the central nervous system again central nervous  system brain and spinal cord where it is processed right where they the information is processed and  once it is processed it passes through through the motor commands through the afferent division  into the different parts of your body now these different parts of your bodies can be divided into  two parts number one one that goes to the skeletal muscle remember again skeletal muscles these  are called the somatic nervous system somatic nervous system is voluntary what does voluntary  me it means that it is under your control I must say to a certain extent okay so this is the  somatic nervous system and then the somatic not the other division is known as the autonomic  nervous system autonomic the world comes from the word automatic so it is involuntary that it is not  under your control so there are two divisions for this - one is parasympathetic division the other  is pathetic division and both of these divisions control smooth muscle cardiac muscles and clan  so what are we learning today we are learning this part the part which is not under your control  which is called the autonomic nervous system or a NS okay this division this division is highly  sophisticated I would say and it is it is it feels like this this division has a lot to give to  our day-to-day lives okay so before even be going to this let me just reiterate what what is the  background of autonomic nervous system so usually autonomic nervous systems comes into play during  chair during situations of emergency but there are several throughout our day to day activities the  autonomic nervous system is required so you you must have read a storybook you know or watched  an episode of a sitcom or a film and your heart started racing okay you were feeling oh my god  I am sweating and it does that happen usually when we are sweating we are breathing heavy is  when we are doing exercise right but this is not that kind of sweating this is we are not doing  exercise but we are still sweating and that is a result of reading a book maybe watching a sitcom  baby and this increase in sweating increase in the heart rate or suddenly you have been told  that sorry that you have to take a test right now your hearts will start racing your palms will  start sweating these actions these actions are not under your control even if you feel that I do not  want to sweat you will still be sweating and this is a radar this is a result of autonomic nervous  system also known as ans we do not have control on these emotions on these actions so now that we  know about a little bit background about autonomic nervous system the question is which part of the  brain controls it it is the hypothalamus and we have learned about hypothalamus hypothalamus  is part of the diencephalon if you remember and diencephalon consists of three parts epithalamus  thalamus and hypothalamus okay hypo word means hypo means below so it is below thalamus  hypothalamus is the part which is responsible for these activities hypothalamus this this part  of the brain has many many functions and we have learned all of them right so just to review it  is just it is called a neuro regulatory or neuro endocrine organ because it produces hormones it  controls hormone release and as a result there are many other functions like sex drive biological  clock temperature regulation naming some which are extremely important roles for hypothalamus the  hypothalamus is controlled and integrated center of the autonomic nervous system and its actions  are automatic and not subject to code conscious control and it receives final fiber bundles  from higher centers such as vision auditory personality which are all part of the cerebral  cortex or setting prom it actually discharges its the information down through the car that  is a spinal cord through the sympathetic and the parasympathetic system so as we said so if  you remember let me go back the slide and if you remember so autonomic nervous system and there  are two division sympathetic and parasympathetic so it receives information from the brain and the  spinal cord and disperses the information through its two division sympathetic and parasympathetic  so what is the difference between the somatic motor system and the autonomic nervous system so  the somatic nervous system involves initiation and transmission so we are looking at the somatic  here which controls the skeletal muscle and autonomic nervous system which controls smooth  muscles cardiac muscles and the glands so for the somatic nervous system it in them the somatic  motor involves initiation and transmission of nerve signals from the CNS to the skeletal muscle  the somatic nervous system controls all boring stuff believe me like picking up a pen or you know  shaking hands or walking etc etc controlled by the skeletal system the autonomic nervous system  this autonomic nervous system called anus is also called visceral nervous system visceral nervous  system because it does all sorts of all sorts of action related to the visceral organs and does  some very very interesting stuff like blushing goose bump last spring etc which are involuntary  and not under your control which is involuntary means the anus any shirts and transmits no signals  from the CNS to the guts heart glands reproductive organs etc the function of the anus is to maintain  homeostasis or a constant internal environment thus the anus controls all physiological processes  that must be maintained by the nervous system to keep the body alive including regulation of heart  rate blood pressure body temperature respiratory rate sweating and digestion the NS keeps these  variables within the optimal ranges and adjust the variables to meet the changing body needs the  anus consists of two parts which is sympathetic and parasympathetic and both of them work opposite  of each other so let's understand some of the so let's understand some of the basic differences  between somatic and autonomic nervous systems so if you look into this slide you will understand  there is a single there's a single lower motor neuron extends from the CNS to the skeletal muscle  fibers in the somatic nervous system its cell body lies in the brainstem or spinal cord here in  the CNS it lies in the brainstem or the spinal cord axons are usually myelinated with a large  diameter for fast transmission of nerve signal in comparison the anus there are to change or to  lower motor neurons and that extends from the CNS to innervate the cardiac muscle smooth muscles  and the clients the first neuron which is called the preganglionic fibers or you can call them  pretend your axons they it's cell body lies in the brainstem or the spinal cord so the first  one's cell body is in the brain or spinal cord and the preganglionic neurons are myelinated and  small and small in axon the axonal length of the preganglionic neuron is much smaller in addition  it releases acetylcholine and until I'm going to discuss more about the neurotransmitters how it  releases how what are its action little later but just remember it releases acetylcholine from  the first or the preganglionic neurons the cell the second neuron is called you can see it in here  the second neuron that is coming out is known as a post ganglionic neuron its cell body resides in  the autonomic ganglia and extends to the smooth muscle cardiac muscle so now the synapse this  region where the preganglionic neuron synapses with the post Ganic ganglionic neuron is known as  autonomic ganglion or sympathetic camión does not matter you can call them any of the names on  the other end if you see the parasympathetic neuron the parasympathetic neuron is you can  see it in here the preganglionic neuron is much longer the axons are much longer it starts  from again the brain and the spinal cord which we will learn little more details later on and  then synapses and the autonomic ganglion but the postganglionic neuron is much smaller it is  the length of the axon is smaller and and then it innervates the smooth muscle with muscles and  glands similar to the sympathetic nervous system so um from here so from here on we are just going  to concentrate on the autonomic nervous system so again what is autonomic nervous system autonomic  nervous system okay let me see why okay so before we go ahead with the detail autonomic nervous  system I just want to show you a little bit of a comparison between the two before we go ahead  so this is the somatic nervous system as you can see so information from the the cerebrum these  neurons are sending information through these lower motor neurons to the skeletal muscles okay  and we have done this before and in the autonomic nervous system you have seen that these are the  visceral motor neurons which are here you can see this if these are coming from the hypothalamus  and then they innervate the preganglionic neurons which forms a ganglion in here which is known  as autonomic ganglion and then passes on the information to the postganglionic neurons to  the smooth muscles grand carrot muscles and fat so these are the parts of the autonomic nervous  system so with this let's learn more about in the autonomic nervous system the autonomic nervous  system as we said is also known as visceral or vegetative nervous system stimulates and control  structure not under your conscious control right it is a motor division and is subdivided into  two parts which is called the sympathetic and the parasympathetic division usually usually  the sympathetic and the parasympathetic sends information to the same organs or structure but  there are a couple of exceptions two or three exceptions which are very important you know  okay the similarities are if he learn first about the sympathetic and parasympathetic  sending impulses to the same kind of same organs for example sympathetic increases heart  rate resulting in increased pulse rate whereas parasympathetic slows down the heart rate so it's  opposite of each other and that's the reason they are known as their antagonist to each other so  they if one increases the heart rate the other is responsible to lower the heart rate okay  sympathetic causes increase dilation of pupil and parasympathetic causes constriction of pupil  so so you can see what is written in here is that these two are work independent of V each other  that is they innervate one single division gland but they work opposite to each other and we will  do how they control together later on okay so so these two division which is sympathetic and the  paths and you point back to slide once more is that you can think of this like tap water okay so  you have hot water right which is sympathetic and cold water let's call it parasympathetic and when  you open both of them it's luke water now if you want the water to be warmer you need to open the  hot tap which is a sympathetic division and if you want to have more cold water you need to open  the qolt app which is parasympathetic so in order for one to override the other one system has  to work more efficiently than the other and it is possible it depends upon the physiological  condition and sympathetic will be the leading factor over the parasympathetic or when the  parasympathetic will be the leading factor over sympathetic so basically sympathetic division is  the one that dominates when a person is in stress okay so let's go over the next slide so this is  usually sympathetic comes into the picture when a person is in huge stress that is into when it's  an emergency condition and usually it's defined by four EPS that is for fear fight flee and sex it's  get called for X so you can write it for number four well the letter on the number four and then  F apostrophe s so for fo you are fear fight flee and sex when one feels threatened the odd man the  body automatically you know prepared yourself for fight-or-flight Pianist of the other end which  is parasympathetic nervous system is for calm vegetative state usually switched on after a big  big meal so anus is when there is an emergency condition and you really need to work immediately  and parasympathetic is a con vegetative state let's take an example suppose there is a lion  right in front of you right now okay and if you think you know now if you start thinking what  should I do should I run or should I just wait you are definitely going to be attacked by the  line so if you're thinking about digestion if you're thinking I let me sit and have my food  get digested and then I will run away it will not happen because if you wait for your launch or  the dinner to be digested you will become yourself become lunch of the lion so as a result it is an  immediate response that is required in order for it to happen for it for you to flee and in order  for this flee to happen in order for you to act immediately sympathetic nervous system one has  to come into play so and in that case whenever the sympathetic nervous system starts working  so you remember in order for you to see there are multiple factors that needs to happen okay so  number one is your mental alertness needs to be super super working very fast heightened that's  the world there has to be increased metabolic rate so that there is enough energy given to  the muscles so that the muscles can act and you can flee and there can be reduced digestive  and urinary function at this point the addition is not required you don't need to comb you know  P so as a result this the energy required to do those phenomenon in a body can wait okay because  this is an emergency situation the energy reserves anything the liver with stored glucose in the form  of glycogen now is able to convert guy Roger into glucose and give it to the muscles which can  use to act but there is increased respiratory rate you can understand at this point you are  breathing heavy heavy heavy heavy the respiratory passageways dilate in order oxygen to go in there  is a increased heart rate and blood pressure of course because we need more oxygen into the  muscles remember these blood vessels are going to go directly to the skeletal muscles in order  for them to act fast sweat glands are activated yes you know the sweat glands you start sweating  the temperature regulation which changes a little bit and as a result the increase in temperature  causes the sweat glands to be activated so this is all about the sympathetic division of the  autonomic nervous system now I want okay so one last thing I want you mention here before we  go there is that sympathetic division as we had learned has two sets of lower motor neurons right  the preganglionic neuron and the postganglionic neurons okay and these actually come out from the  spinal cord which is called the throstle lumbar region that means it comes from the thoracic  region and the lumbar region so you can see it's called a wrassle lumbar division what comes  out the preganglionic fibers of the sympathetic nervous system comes out from the thoraseal lumbar  region these are the presynaptic neuron they form a chain which is known as autonomic chain and  then the postganglionic neuron then innervate the different organs in your body and does the  task okay so apart from this the the sympathetic division is divided as you can see this is a  thoraseal lumbar region that the preganglionic neurons are coming out is divided into three  major parts one is known as a sympathetic chain gang gear which is spared that means one comes  out from the right side the other comes out from the left side the collateral ganglion which is  unpaired that means usually there is only one of them coming off from one part of the body  it is usually from the anterior cart and the last is a medulla which is again paired remember  adrenal medulla just recapping adrenal medulla is an organ or a gland which is situated on top  of the kidneys okay and it is a neuro endocrine gland which we learned before and these are pre  ganglionic neuron the third part is the adrenal medulla which call it is again paired because  we have two of them in left and right so what is the difference between them so let me go to  the next slide so you will understand so on the three different kinds of autonomic nervous system  is the sympathetic preganglionic fibers which was a first one originate from the lateral horns  and become part of the spinal anterior roots and this the they are myelinated the preganglionic  neurons are myelinated and they form a sympathetic chain so you can see this chain formation that  is there the sympathetic chain is formed and then they pass out through the you know then these  fibers diverged extensively actually with and then synapse into the different organs as you can see  it in here okay so the sympathetic chain ganglion which was the first month sympathetic a his chain  ganglion is also called periban vertebral ganglia again sympathetic chain ganglia is also called  Kara vertebral ganglia which lie on each side of the vertebral column neurons of these gland  clear ganea control effectors of the body wall thoracic body head neck and limbs these are all  four that are controlled by the sympathetic chain Gandia the next is collateral ganglia these are  also known as pre vertebral ganglia our anterior to the vertebral column C so these if you look in  here these are all part of the collateral ganglia and collateral ganglia contains cannula neurons  that inter innervate abdominal pelvic tissue and viscera so you can see the abdominal pelvic region  this is the abdominal region this is the pelvic region and they innervate each one of them okay  and since the abdominal pelvic region each one of them is one for example you know we have one  stomach and we have one your uterus we have one urinary bladder so these are not fair just so they  are one in number and they come out to that terior part the last is adrenal medulla which is very  interesting the center of each adrenal gland which is called the adrenal medulla so adrenal gland is  divided into two parts one is the adrenal cortex which is the outer part of it and the inner part  is called the adrenal medulla so we are talking about the inner part here which is the adrenal  medulla it is a modified sympathetic ganglia okay the ganglionic neurons of the adrenal medulla  have very very short axons when these minerally cells are stimulated when these cells of the  head renal medulla is stimulated they secrete neurotransmitters directly into the bloodstream  and they do not actually synapse so if you look into the so if you look into the red fiber  that is in here so basically pre ganglionic neurons are coming and having you know directly  it is stimulating the adrenal medulla this mode of release allows neurotransmitter to function as  hormones affecting target cell throughout the body so basically these transmission from the adrenal  gland or adrenal medulla is very effective because the adrenal medulla is able to produce hormones  which is epinephrine and norepinephrine both of them are very very important for fight-or-flight  response which is during stress and it happens it does not synapse it the preganglionic neurons  directly come and activate the adrenal medulla t-cells which in turn actually causes the  release of hormones from the adrenal medulla so with that high continuing with the  parasympathetic division of the autonomic nervous system so the second part we have already  learned the sympathetic nervous system so we are going ahead with the parasympathetic nervous  system so as you can see it in here there are the parasympathetic is also known as a cranial  sacral division because the nerve innervations that come out from the different parts of the  nervous system is mainly from the brainstem of the brain and the sacral division of the spinal  cord so the question is which part of the brain which is brainstem and all the three regions  which is midbrain pons and medulla oblongata all three of them are involved in the autonomic  housing of the autonomic nuclei so all parts of the brainstem the midbrain pons medulla oblongata  contain autonomic nuclei associated with several cranial nerves and and some of the segments of the  spinal cord which is the last segment which is the the sacral part of it is involved in the autonomic  function so say it will just review of the spinal cord the spinal cord is divided into cervical  thoracic lumbar and the Sikh religion so these know fibers come out from the sacral division of  the spinal cord okay so further interesting things to understand in here is parasympathetic is mainly  mainly responsible for to conserve energy it is a part which promotes sedentary activities I want  you to understand this that once the sympathetic is initiated and completed there needs to be a  phrase of rest and that is essential and that is what parasympathetic division is okay it helps  the body to basically reset itself to start the next cycle so if you look at the next slide here  so there are five different responses associated with it one is a decreased metabolic rate so  if you remember it's just pretty much opposite of what sympathetic division was here there  is a decreased metabolic rate decrease heart rate and blood pressure increased secretion of  saliva and digestive glands increased metabolic increased secretion of saliva and digestive class  was a third one there is increase the blood flow in the digestive tract because there is in his  digestion and there is increased urination and defecation so this these are the different five  responses that is related with the parasympathetic division the parasympathetic division as we  just said that it is involved you know in the brainstem and in the sacral division interesting  to understand here is the the preganglionic fibers of the parasympathetic division do not diverge  as extensively as to the sympathetic division a typical pre guided fiber synapses with maybe six  or seven different six to maybe eight of them in the region which is called the terminal ganya  organic neurons around here it's synapses it's longer and then it goes to the target organ there  are several cranial nerves which are involved in this entire process because it comes out from the  brainstem cranial nerve three seven nine and ten are actively involved in the process and you can  see the target organs are I tear glands a library grandpa wrote it down several visceral organs  of the neck thoracic cavity are all part of the brainstem which controls the autonomic division  of that the other part is a sacral division which actually forms an intramural ganglia which in turn  actually controls the visceral organs associated with the abdominal pelvic cavity so with that  if you see this figure you will understand and sorry if you see this you will see that this part  which is coming these fibers which are coming out from the brainstem control these organs the ones  that which are said and the ones that are coming from the sacral region is more associated with  the abdomen or pelvic cavity in our body okay so before we go into the last part I would like  to actually specify some important information is that again parasympathetic division is involved  in rest it was mainly antagonist Lee with the sympathetic division there are certain exceptions  which will probe it later and as such this is absolutely necessary and it is a craniosacral the  innovation comes out from the same no structural division and and the preganglionic neurons  or axon are much longer than the post can be only neurons so going ahead with the the next  part which is kind of really interesting and you know when we have started initially studying  about the autonomic nervous system we always said there are two divisions one is sympathetic the  other is the parasympathetic division now comes another division which we completely you know  you v usually do not mentioned in here which is kind of a third nervous system division which is  known as the enteric nervous system the ENS okay the ENS is an extensive network of neurons and  north wall networks which actually is part the network of nerves that go to the digestive system  although the sympathetic and the parasympathetic control on the ENS activities but the units at  least still can coordinate many visceral reflexes locally without without and the instruction  of the CNS so pretty much it can work on his own so altogether there are about 100 million  neurons involved in its you can understand it is it is an important part of the homeostasis  and there are several neurotransmitters that are found in the brain works in conjunction  with the ENS okay so this actually shows you basically kind of our review of sympathetic and  parasympathetic division how they are the from each other and I'm going to actually go over  the differences between them a summary of the sympathetic division and the parasympathetic  division okay so let's do one at a time the sympathetic division of the anus includes two  sets of sympathetic chain ganglia one on each side left and right of the vertebral column and  there are three collateral ganglia anterior to the vertebral column and to adrenal medulla that  is that is also very important adrenal medulla actually acts as an important sympathetic division  and no parasympathetic division actually comes to the adrenal medulla the preganglionic fibers is  the second one the peak angular fibers are short because the ganglia are close to the spinal cord  the postganglionic fibers if you remember now if you see this these four scan groanings though  these are the preganglionic fibers which are shown in yellow and the ones that are shown in  green are the postganglionic neuron so the pre Gangnam kernels are relatively short they form  of anionic change very near to the spinal cord but the postganglionic neurons actually are longer  and extend a considerable distance add and go to the target organs okay the sympathetic division  shows extensive divergence okay there is a huge amount of divergences then they come out pretty  angliana cow and they diverge to different several different organs in place one actually even one  preganglionic fiber can actually innervate or go to dozens of of the postganglionic fibers  to the target cell the third fourth point is all predominantly RIANZ release ACH all every  one of them the postganglionic neurons on the other hand can release ACH but mainly releases  norepinephrine so mainly the postganglionic neurons of the sympathetic division releases  norepinephrine neurotransmitter okay so this is mainly some of the major parts of the sympathetic  division so now if we do the parasympathetic division the parasympathetic division includes a  visceral motor nuclei and they are associated with the cranial nerves 3 7 9 and 10 and the sacral  division also from s2 to s4 okay the ganglionic neurons are located in the ganglia so you can  see these small places where the synapse is the ganglia and and then they go to the target organ  then they reach the target are the parasympathetic division does innervate but the divergence of  these are these fibers are not so much so each one of them actually go to a particular organ  from the free then to the post they go in there the important thing to remember is the  preganglionic neurons are very long and the postganglionic neurons are very sharp so the  ganglia that forms is near the target organ okay okay so actually the parasympathetic division has  approximately one-fifth of as much as diversion as sympathetic so sympathetic diversion or  branching of these fibers to different organs is much higher than that of the parasympathetic  division on all parasympathetic division neurons are calling a chip that means whether it's pre  ganglionic neuron or postganglionic neuron both release acetylcholine and the new receptors as  we know are muscarinic receptors and in your muscular junctions and it can be nicotinic  receptors also okay so mainly the effects of parasympathetic division is for rest and and  mainly the function of sympathetic division comes into picture during emergency sympathetic  division in general is involved in more functions like increasing in the heart rate increase  in respiration parasympathetic on the other hand is responsible for mainly for mainly rest  vegetative state or to reset the entire process so with that we go to the last section here which  is the autonomic division working together so the first part as you can see is what we have just  learned how the sympathetic and parasympathetic work and tagging asleep to each other opposite of  each other here you can see a very good example of how sympathetic increases the heart rate acceptor  that explosive the heart rate parasympathetic also increases digestion but sympathetic decreases  that in addition so it's antagonists they both can't act in a split with each other but there  are some occasions are some of the phenomenon in which they work together and that is  called the co-operative effects okay the co-operative effects is seen in when the both the  sympathetic and the parasympathetic stimulation causes different effects that together you know  combination they work synergistically they work as a as a team and have one distinct result  the best example is the sexual function of the male reproductive system the male penis becomes  erect as a result of parasympathetic division or innervation and ejaculation of the semen from  the penis occurs as a result of sympathetic innervation so initially the initial part is  taken care by the parasympathetic division where the erection of the peanut penis happens  and then the ejaculation process and for the ejaculation process the sympathetic division  has to come into the picture the dwell effect the combination of that a synergistic effect  of this is the process when the semen comes out