 this session on the functional components of cranial nerve nuclei. There is one of the topic which students find it most difficult in neuroanatomy. So I have decided to take up this topic for you all. So in this session we will be covering all the functional components. So which all are the functional components? Here we can see the list. There are three motor columns and there are four sensory columns. So all these functional components will be covering in this particular session. Before beginning with the functional components a little knowledge about the embryology is essential. So we will see that. So during the development of the brain and the spinal cord in the neural tube we can see there is a longitudinal groove which is referred to as sulcus limitance. Okay here we can see this is the development of spinal cord and this mark structure this is the sulcus limitance which divides the lateral wall of the neural tube into a dorsal ailer lamina and a ventral basal lamina. Okay so this is a basal lamina and this is the ailer lamina. Basal lamina is motor which will have motor nuclei and ailer lamina sensory will be having sensory nuclei. Okay so this is in the neural tube and this is in the region of spinal cord. Okay and when we see in the region of the brain stem this neural tube opens up like this on each side. Okay it will open up in this way so that the ailer lamina which is seen it is deviated to the lateral aspect. Here we can see this is the ailer lamina and basal lamina is on the medial aspect. This is in the region of the brain stem here we can see the cavity of the fourth ventricle and here this structure is the sulcus limitance. When we study the floor of the fourth ventricle there is a structure which is referred to as sulcus limitance medial to which there is a basal lamina which contains a motor nuclei and lateral to it there are sensory nuclei. Okay so this basic knowledge is important before studying the functional components and we should be knowing about the various difference between the functional components in spinal cord and functional components in brain stem. We all know there are in all seven functional components but in spinal cord there are four functional components. Okay there's some additional functional components in brain stem. So here we can see the functional components of the spinal cord. In spinal cord all functional components are general. Okay all four components are general whereas in brain stem few additional special functional components are added up and that's how it becomes seven in number. So four general are general somatic afferent, general visceral afferent, general somatic efferent and general visceral efferent. Okay these four are the components in spinal cord. There's some additional special components which are added on in the brain stem and that's how it becomes seven in number. Two special components we can see special visceral efferent. So here we can see general somatic efferent and general visceral efferent. In between them there'll be a component special visceral efferent. Similarly here there'll be a component special visceral afferent. Okay and there is one more special component which is on the lateral most part this is referred to as the special somatic efferent. So these are all the seven functional components in in the brain stem okay and therefore functional components are in the spinal cord. Now let's explore each functional component one by one. So motor components as you all know they are three in number. So I've listed down all the three. So depending upon the name of the functional component we can derive what is the function of that component. So whenever there is a component which is referred to as special visceral efferent it refers to the muscles of the pharyngeal arches. As you all know the pharyngeal arches have got separate nerves. The nerve of the first arch is mandibular nerve that's the branch from the trigeminal nerve. Then seventh now facial nerve is the nerve of the second arch. Glossopharyngeal nerve nerve of the third arch and nerve of fourth and sixth arch together is the vegas nerve. Okay fourth and sixth arch together the nerve is vegas nerve. Fourth arch is superior laryngeal nerve sixth arch is recurrent laryngeal nerve. So all the muscles supplied by these nerves will have the component special visceral efferent. So there's one keyword for special visceral visceral efferent that is pharyngeal arches. Then general visceral efferent. Just appreciate the name general visceral efferent. This refers to the supply to the parasympathetic supply to the smooth muscles and the glands of the body. The parasympathetic supply is also referred to as the craniosacral outflow. The cranial is formed by the three seven nine and the tenth cranial nerves okay. Three seven nine ten they form the cranial parasympathetic outflow and those are included in general visceral efferent column. All the glands the submandibular glands sublingual parotid and glands in the GI tract glands in the respiratory tract all will be supplied by this component. General visceral efferent component okay. Then general somatic efferent means soma refers to the body wall. So muscles which are derived from the somites those will be supplied by the general somatic efferent component. So in the head and neck region there is extracular muscles and tongue muscles. Extracular muscles those applied by the third fourth and the sixth cranial nerve and tongue muscles are supplied by the twelfth cranial nerve hypoglossal nerve okay. So these nerves will have this functional component general somatic efferent component. So this was just a basic idea of the motor of the efferent columns. Now let's see the sensory or the efferent columns. So sensory columns are four in number. First I have listed down special visceral efferent. Special visceral efferent refers to the taste sensations. Taste is a special sensation. So taste sensations are carried by the seventh nerve, ninth nerve, tenth nerve okay. Then general visceral efferent this refers to the general sensation. What do you mean by general sensations? Pain, touch, temperature okay. All these are included in general sensations. Just for an example if you are having a coffee the temperature of that coffee is a general sensation. But the taste of the coffee is a special sensation okay. General visceral efferent is general sensations from the viscera. General somatic efferent, general sensations from the body wall. The pain, touch, temperature sensations from the outer aspect of the body. If you see the head and neck region the cryominal nerve, the fifth cranial nerve has got this component general somatic efferent component okay. The other nerves as well but this is the major nerve having general somatic efferent component. And special somatic efferent this refers to the special sensations from the body wall. What do you understand by special sensations from the body wall? The sensations from the ear. The auditory sensations those are included in special somatic efferent. Also also actually an optic are included here okay. In this image we can learn about the various location of the nuclei of the functional components. So all those nuclei which we learned now are listed here. These are the motor nuclei and these are the sensory nuclei. Okay in motor GSE, GSE was muscles derived from the somates. So third, fourth, the sixth cranial nerve they supply the extrocular muscle. The twelfth cranial nerve supplies the tongue muscles okay. Then SVE was for the pharyngeal arches. Now the pharyngeal arches are fifth nerve, seventh nerve, ninth and the tenth now okay. The eleventh cranial accessory nerve also joins with the tenth nerve that's why it is included here. This is the muscles derived from the pharyngeal arches and GVE this is the cranial parasympathetic outflow. Cranial nerve three, seven, nine, ten which supplies the glands and the smooth muscles in the body okay. In salivatory nucleus there are two salivatory nucleus there is superior salivatory nucleus inferior salivatory nucleus and they have shown three here because they have shown one lacrimatory nucleus as well. Lacrimatory nucleus is the part of superior salivatory nucleus. So third now fourth sorry third now seventh, ninth and tenth these cranial nerves are included in GVE column. Then coming to the afferent columns these two columns special visceral afferent and general visceral afferent they have only a common nuclei and that's why the name of the nuclei is referred to as nucleus of practice solid areas okay. The cranial most part of this nuclei receives the special sensations SVA the taste sensations are perceived by the cranial most part of this nucleus of practice solid areas as the remaining part will receive the general visceral afferent that is the pain touch temperature from the viscera. The general somatic afferent I told you the fifth now the trigeminal nerve is the major nerve which is it carries these general somatic afferent fibers and here we can appreciate the size of this trigeminal nucleus it occupies the midbrain as well it occupies the pons as well as occupies the medulla oblong data and some part also extends in the spinal cord okay. So this is the largest of all the cranial nerve nuclei and it has got three components there's a mesenchepalic nucleus there's a chief sensory nucleus there's a spinal nucleus of trigeminal nerve since there are three components it will be having three different functions as well the mesenchepalic nucleus responsible for proclioception the chief sensory nucleus responsible for the touch tactile sensation its spinal nucleus is responsible for pain and temperature okay and in special somatic afferent there is the vestibular nuclei vestibular and the cochlear nuclei are included in special somatic afferent okay. So this is just a summary of all the cranial nerves with their functional components we'll quickly try to revise it olfactory optic and the vestibular cochlear nerve these three have same functional component special somatic afferent okay oculomotor nerve has got general somatic efferent as well as general visceral efferent trochlear nerve only general somatic efferent supplying the extrocular muscle and trigeminal nerve has got two functional components general somatic efferent and special visceral efferent whenever special visceral efferent is there that means pharyngeal arches okay muscles derived from the pharyngeal arches will be supplied by this component then facial nerve glossopharyngeal nerve and vegas nerve the functional components looks extensive but to try to logically remember the you can see the glossopharyngeal nerve and vegas nerve have got almost same functional components except the vegas nerve has got one component extra that is the general somatic afferent because it carries some sensation from near the ear okay special visceral efferent refers to the pharyngeal arch GBE refers to the glands and muscles of the GI tract as well as the respiratory tract and special visceral afferent whenever special visceral afferent is there that means it refers to the taste sensations and general visceral afferent is pain temperature and all okay so depending upon the area of supply of the nerve we can determine the various functional components let's see the facial nerve special visceral efferent because it is supplying muscles of the pharyngeal arches GBE because it supplies the glands the submandibular gland sublingual gland lacrimal gland okay special visceral afferent because taste sensation from the anterior two-thirds of the tongue then general somatic afferent certain uh sensation from the skin around the ear is carried by facial nerve okay then accessory nerve accessory nerve has got two components cranial accessory and spinal accessory cranial accessory has got this component special visceral efferent and spinal accessory has got this component general somatic efferent hypoglossal nerve has got only one component GSE that will supply muscles to the tongue so this was all about the functional components of the cranial nerve nuclei so I've tried to concise the topic so that the basic concepts of the cranial nerve nuclei becomes clear to you all okay so if you all have any doubts you all can ask in the comments section below okay thank you