 Postural reflexes are the ones which correct our posture basically they align our head with respect to our trunk and also the alignment of the head with respect to the space surrounding us that is with respect to the gravity and it is because of this postural reflexes that we are able to maintain our posture and able to carry out various voluntary acts because for voluntary action also there is a particular posture we need is suppose we are trying to pick up something right so we need to maybe bend our trunk a little bit so for that moment also there is particular alignment of the trunk head the alignment of the head with respect to the trunk and alignment of the head with respect to the space so this all is brought about by unconscious postural reflexes we need not be conscious about a posture for every voluntary action isn't it? So how did we come to know about these postural reflexes? These were basically done by Sherrington and Magnus what they did was they sectioned the animal neural access at various levels so you might have heard these terms known as a spinal animal, de-celebrate animal, de-cortic animal so what is that basically they separated the part of the neural access with the other part so in a spinal animal the section was made in the spinal cord so that there was no input from the top right so the sections what we are going to study will be the sections at the spinal cord the de-celebrate animal where the section is made below midbrain then there is de-cortic animal where the section is made above midbrain that is only the cortex is removed and the final one is intact because there are certain reflexes which we see only in intact animal they are not seen even in de-cortic animal that means cerebral cortex is playing part in those kind of reflexes so broadly if we see what are the types of these reflexes so it is broadly classified as static reflexes and statokinetic reflexes and then in static reflexes it is further classified into local reflexes, segmental reflexes and attitudinal reflexes are also known as general static reflexes now in this local reflex we have three types by the way local means that the limb which is getting this stimulus the response is only in that particular limb so only that particular side and one level of the spinal cord is involved so that is known as the local reflex, segmental reflex means that the stimulus might be in one limb but the response we are getting from the contralateral limb so that is segmental reflex or it is extending to the various segments of the spinal cord on the ipsilateral side only right it is not limited to one level of the spinal cord so that is also segmental and third one is attitudinal or general static reflexes very important so in local reflex we will see three reflexes that is stretch reflex the details we will not see because for that there is another video then there is positive supporting reaction then negative supporting reaction in segmental reflexes we have a cross extensor reflex then there is rhythmical stepping and there is locomotor pattern generator in attitudinal general static we have tonic labyrinthine reflex tonic neck reflex long loop stretch reflex and writing reflexes then stato kinetic stato kinetic we have three reflexes vestibular placing reaction visual placing reaction and hopping reflex and just for simplification just remember that this stato kinetic reflex the integrating center is basically the cerebral cortex so these reflexes are seen only in intact animal but what about the other integrating centers so we saw that we have we have reduced these reflexes in various types of animals by sectioning the neural axis so in a spinal animal where we have made the section at the level of the spinal cord what we see is static local and static segmental reflexes so these reflexes that means the integrating center for them is present in the spinal cord so here this is showing the integrating center right static local and static segmental reflex the integrating center is the spinal cord then in de cerebrate animal in which the section is made below the midbrain there we see tonic labyrinthine reflex tonic neck reflex and long loop stretch reflex that is in the attitudinal reflexes we see these three kind of reflexes whose integrating center is in the medulla but one kind of attitudinal reflexes that is the writing reflexes are not seen in de cerebrate animal that is they are seen in de corticate animal so for writing reflexes they should be presence of midbrain so midbrain is the integrating center for the writing reflexes except one except one so we will see that there are five types of writing reflexes and only one that is the optical writing reflex is not seen in de corticate animal for that we need the presence of the cerebral cortex so in intact animal we see stato-kinetic reflexes and optical writing reflex so integrating center for these reflexes is cerebral cortex long let's come to the responses which occur in these reflexes so first is static reflex stretch reflex positive supportive reaction and negative supporting reaction now stretch reflex as we know what happens that there is a muscle spindle right so this is supposed muscle and inside there is presence of muscle spindle and from here 1a and 2 fibers basically carry the information to the spinal cord then from there this afferent makes contact with the alpha motor neuron which supplies the extrafusor fibers of the muscle so this is a monosynaptic stretch reflex so what are the receptors receptors are basically present in the muscle spindle integrating center is the spinal cord and what is the response response is the contraction of the muscle same muscle from which the afferents are coming and basically the stimulus is stretch of the muscle right stimulus is stretch of the muscle which will stimulate the muscle spindle and it will lead to contraction of the same muscle then coming to positive supporting reaction positive supporting reaction what it does is it helps in stabilization of the joints suppose there is a person standing okay and for standing we need both the contraction of the flexors as well as extensors okay so this positive supporting reaction is basically when we are standing straight for the stabilization of ankle joint both the flexors and extensor muscles contract that is positive supporting reaction so what is the stimulus basically that of the ground when we are standing straight so the receptors here is five receptors right and proprioceptors receptors are there which will give the stimulus integrating center again is the spinal cord so it is easy to remember that all the static reflexes local static reflexes integrating center is the spinal cord and response is both the contraction of the flexors and extensors and stabilization of the ankle joint and what is negative supporting reaction negative supporting reaction is when the positive supporting reaction disappears and when will that happen say I told you that positive supporting reaction is basically for the stabilization of the ankle joint when we are standing but when we are walking we want differential contraction of the flexors and extensors right then in that time we don't want that both the muscles should contract equally isn't it. So when we start walking there is a stretch okay there is a stretch of the muscle and again there is activation of this muscle spindle and it leads to contraction of flexors first and later extensors right. So that is again the integrating center is a spinal cord. Coming to segmental reflexes right. So what are the segmental reflexes? What is the integrating center? Again I told you for the segmental reflexes also integrating center for all is spinal cord right and what are the receptors? Receptors are basically in cross extensor we have nociceptors. Nociceptors what happens is when we touch a painful object what happens? That there is flexion of the same limb but there is extension of the opposite limb. So why we have to have such kind of posture maintenance? Because when we flex certain limb there is change in the center of the gravity and to maintain the center of the gravity there is extension of the contralateral. So that is cross extensor reflex. So at the level of the spinal cord let me just draw suppose there is painful stimulus okay and it goes to the spinal cord and I told you that what happens so that it via interneuron it makes contact with the flexors of the same side and via other interneurons it may contact with the extensor alphanotoneuron on the other side right. So there will flexion of the same limb and extension of the opposite limb. Then with nickel stepping pattern now what was done was that in the spinal animal so suppose this is the spinal cord and the section was made here. So for further studying that what will happen suppose if we cut or we isolate one side of this spinal cord with the other side. So this central part of the neural axis was dissected and a stimulus was there a stretch stimulus was given to one limb and what we see that there was a rhythmical alternate flexion and contraction of the same limb. So even the same limb will flex and contract such that there is a stepping pattern of the ipsilateral side. So that is known as rhythmical stepping pattern and what was the receptor? Receptor word muscles, spindle or what we can say is proprioceptor stretch right and response was flexion and extension of the same limb right same limb so that is a stepping pattern which we get. Then locomotion pattern generation is basically the this spinal cord is intact okay so this dissection was not made. In fact what we saw that there was stretch when there was a stretch on one side then there was alternate flexion and contraction of the two limbs so when this side limb flexes there is extension of the opposite side limb right and when there is extension on this side then there is flexion of this side. So you might have seen animals basically how they walk on four limbs that one one four limb is extended the same side hind limb is flexed and the opposite side hind limb is extended. So there is like alternate pattern one four limb extended opposite four limb flexed right same side four limb which was extended the hind limb is flexed and the opposite side hind limb is extended. So that posture is important for maintenance of center of gravity for walking and for us also you see that when we walk we move our hands also the pattern is similar to that of the animals so integrating center for that is present in the spinal cord and what will be the receptor or a stimulus again stimulus is extension and receptor are the proprioceptors. Moving on to the next kind of reflexes that is the attitudinal reflexes which are seen in decelerate animals. So these as I told you these are tonic labyrinthine reflex also known as vestibulo spinal reflex then there are tonic neck reflexes also known as cervical spinal reflexes and there are long loop reflexes. So as the name suggests tonic labyrinthine labyrinthine reflexes so receptors are basically present in the vestibular organs right so otolith organs are the receptors right and what will be the stimulus obviously the change in position of the head with respect to the gravity so those are the stimulus so like a linear acceleration then angular acceleration or tilting of the head so that is basically being detected by the otolith organs and is responsible for the response we will see what is the response depending on where the head is with respect to the space and the tonic neck reflexes are basically the position of the head with respect to the body so please try to understand this that with respect to trunk when we say with respect to trunk then it is the activation of the tonic neck reflexes and when we say with respect to the space the position of the head then it is tonic labyrinthine reflexes so this we are going to see in detail by the way tonic neck reflexes what is the receptors it is the proprioceptors because when we move our neck you can stretch your neck flex your neck to one side then you can ventro flex your neck dorsiflexion there will be the stretch of the neck muscles right and the proprioceptors will be activated so this we are going to see in detail but before moving further let us see what is this long loop reflexes basically when we are standing as I told you in positive supporting reaction that there is a contraction of the flex and extensor fine but because of change in tone of the muscles there is some swaying from side to side and this swaying from side to side is instantaneously corrected by this long loop stretch reflexes again the proprioceptors are the receptors for this plus also the vision right there is visual receptors also which are important for these reflexes and this you can correlate with the rhombus sign okay rhombus sign is what we are checking we are checking for the integrity of these proprioceptors and visual receptors so for this test is basically done with both eyes closed and eyes open isn't it rhombus sign is positive when we say that the person sways with eyes closed so that means that by closing the eyes we have removed this stimulus right and with normal people physiological condition because of the action of the proprioceptors the person will stay in midline but if proprioceptors are dysfunctional then we will have the person swaying isn't it so that is long loop stretch reflex and what is the integrating center for all of these reflex tonic labyrinthine tonic neck and long loop reflexes well the integrating center as I told you in de-cerebrate animal the integrating center for all of these is medulla medulla okay and there are certain efferents also because that will change the tone of the muscles for long loop stretch reflexes we have corticospinal tract okay but for tonic labyrinthine and tonic neck reflexes we have vestibulospinal tract and reticulospinal tract and in reticulospinal tract again we have to pontine reticulospinal tract and medullary reticulospinal tract so these are the efferents which will cause a change in the tone of the muscles fine now let us try to understand basically these tonic labyrinthine and tonic neck reflexes what is the response with position of the head with respect to trunk and with respect to space okay so first things first and then we will go on to see that how the responses will be when the head position and neck position are different with respect to trunk and with respect to space so first of all in tonic labyrinthine reflex remember that the whichever side the neck will tilt right suppose the neck tilt to left side then there will be extension of the left side limbs and flexion of the right side limbs understood so whichever side the neck is going to tilt there will be extension of the same side and flexion of the opposite side in tonic neck reflexes we will get opposite so in tonic neck reflexes if the neck tilt is to left side then we will get the flexion of the left side and extension of the right side please remember this and with this only we are going to try to understand tonic labyrinthine and tonic neck reflexes suppose now this is a position where this is telling the position of the head so right now it is in midline and this is the position of the trunk okay so you see trunk and head are properly aligned and the angle between them is 90 degrees so that means head is aligned with the trunk in midline now suppose what happens that both the trunk and the head tilt both the trunk and the head tilt so you see what is happening that the angle between the trunk and the head is 90 degrees right so is there any stretch of the neck muscles no there is no stretch of the neck muscles so tonic neck reflexes are not active in this condition but tonic labyrinthine reflexes will be active in this case because the head has moved with respect to the space so tonic labyrinthine reflexes will be active and what will happen suppose we'll keep this as left and this side as right okay left right now if the head has moved to right side what will be the response there will be extension of the right limbs and flexion of the left limbs so when the head moves to right the animal what will happen sorry when it's like this okay it has moved the animal the same side limb will extend and the other side limb will flex and this is going to keep the animal stationary so that is tonic labyrinthine reflex let's come to another example in this you see head is in the midline okay with respect to space it has not moved but the trunk has moved trunk has moved okay trunk has tilted to right or we can say actually head has tilted to left head has tilted to left you see the angle here is 90 degree isn't it so please try to understand normally we say tonic neck reflexes with respect to neck tilting so even when i am saying that trunk has tilted to the right that means head has tilted to the left you see this side angle has increased it is greater than 90 degree so head has tilted to the left so what will be the response in this case also the response will be extension of the right limb because as i told you the responses of the tonic neck reflexes are opposite when the neck tilts to left as happens in this side flexion of the ipsilateral side so here they will be fixed in and extension of the contralateral side so extension of the right limb and flexion of the left limb will happen so in this case only only tonic neck reflexes are active not tonic labyrinthine reflexes now consider this situation fourth situation in which what is happening that only the head has moved trunk has not moved right so in first situation both were in alignment and in midline in the second situation both trunk and head have moved such that the angle between the head and trunk is 90 degrees okay so if it is 90 degrees we will get only tonic labyrinthine reflexes in the next one only the trunk has moved head is in the midline so with respect to space it has not moved right now in the last one you see only the head has moved when only the head has moved so with respect to space it has moved definitely with respect to space it has moved and with respect to trunk also it is moved so here it is 90 degrees so this movement with respect to space will initiate the tonic labyrinthine reflexes and what will be the response so this is right side right so in tonic labyrinthine we say that neck movement to right side what it will cause extension of the right limb and there will be activation of the tonic neck reflexes also so neck movement to right side what it will cause extension of which side it will cause extension of the left side opposite we get right so it will cause the extension of the left side and flexion of the right side and this will cause the flexion of the left side so basically the responses of tonic labyrinthine and tonic neck reflexes will cancel each other right so in both the limbs the person is the animal is standing straight he will keep on standing straight only so with the trunk in position and with only head movement we don't get any change in the tone of their limbs because of the cancellation of the responses of tonic labyrinthine and tonic neck reflexes so that was about to the movement on to the left and right side what about the flexion and extension movements so what we see in tonic labyrinthine and tonic neck reflexes with head flexion and extension right so the tonic labyrinthine reflexes same thing you try to understand what I have said in the tonic labyrinthine reflex whichever side the neck is moving that side there will be extension of the limbs so when we say neck flexion suppose there is neck flexion so it is moving towards the front right so I try to remember like that neck flexion is towards the front so four limbs will extend in tonic labyrinthine reflex and the tonic neck reflex they will four limbs will flex okay same side it will flex in tonic neck reflex and with the neck extension that is the dorsiflexion we can say four limbs are going to flex and in tonic neck reflex four limbs are going to extend so you can imagine this example as an animal howling state what happens when the animals howl they extend their neck to the back and in that case the four limbs are kept extended while hind limbs are flexed right so that is basically tonic neck reflex what we are seeing so basically these tonic labyrinthine and tonic neck reflexes operate together and maintain our position now let's move on to next reflexes that is the writing reflexes so what are these writing reflexes writing reflexes are the writing of the body that is bringing the body in alignment the head in alignment with the trunk and head in alignment with the space so that is known as writing so there are five types of writing reflexes labyrinthine writing reflex body on head writing reflex neck on body writing reflex body on body writing reflex and optical writing reflex and the name suggests that where is the receptor and where is the response so first thing labyrinthine writing reflex what is the receptor otolith organs are the receptors okay and this reflex corrects the position of the head in space okay then body on head writing reflexes body on head writing reflex that means the receptor is in the body and the response is in the head so suppose in this case like the animal is being dropped so what is happening you see first is correction of the head with respect to space because of the linear acceleration the animal is having you see first the head is corrected with respect to space then there is differential stimulation of the various parts of the body you see that when it is coming in contact with the air and this part is falling isn't it so there is differential stimulation of the different parts of the body so basically here the receptors are pressure and classically this will be seen if you see if the person if the animal is lying on a floor and the body is tilted on the floor to the side so one side there will be much more pressure compared to the other side right so that is the receptor is in the body and there will be the correction of the head the head will be brought in alignment with the body so it is not that when the body is tilted head will be left behind head will come in alignment with the body so that is body on head writing reflex the neck on body writing reflex as I told you that there is a twist between the neck and the body so there will be receptors in the neck so appropriate receptors in the neck will be there and they will also correct the position of the body with respect to the head so neck on body writing reflex and body on body writing reflex that is even if the head is prevented from tilting so like in this case when the body is tilted and head is left behind so you are holding the head and not allowing its movement to occur then the position of the body itself is corrected so that is body on body writing reflex so pressure receptors in the body and the response is changing the position of the body so these are basically writing reflexes and best seen when the animal is made to fall so a series of reactions occur first is labyrinthine writing reflex so always first the position of the head is corrected then body on head writing reflex neck on body and then body on body writing reflex and you see finally the animal is landing in the correct position so for all these reflexes where is the center as I told you it is seen in decorticate animal and it is not seen in decerebrate animal so the center is in midbrain fine and then there is optical writing reflex basically the visual cues bring about the correction in the alignment of the head and body and it is very very important in case of the humans and the center for this is cerebral cortex because the information from vision should go to the visual cortex and from there it actually reaches to the tectonucleus so cerebral cortex is the center for the optical writing reflex and then finally we have the statokinetic reflexes and as I told you where is the center for these reflexes if they occur in intact animal so it is center is cerebral cortex and these are the placing reactions vestibular placing reaction and visual placing reaction placing reaction basically means placing of the foot on the ground so here you see that placing of the foot of the ground by the newborn right so the receptor for vestibular placing reaction is the otolith organs and there are visual cues involved suppose the labyrinthine is destroyed then also with the eyes open we see this visual placing reaction if there is a person who is blind folded and the vestibular apparatus is destroyed then in that case both the cues will disappear and we will not see the placing reaction in newborns and then finally there is hopping reflex what is hopping reflex? Hopping reflex is suppose you might have experienced suppose you are standing and suddenly you are thrown off balance so the person hops on one foot so that is hopping reaction