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what's up Ninja nerds in this video we're going to be talking about homeostasis before we get started if you guys like this video it makes sense to you it truly benefits you please support us one of the best ways that you can do that is by hitting that like button commenting down the comment section and please subscribe really really helps us to continue to keep making free videos for all of you guys enjoyment so please do that also you guys want some awesome
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notes some illustrations to check out while we kind of go through this lecture together go down the description box below to take you to our website where we have some great notes and illustrations but let's talk about homeostasis when we talk about homeostasis what is homeostasis it's basically the state of balance right so you want to be able to maintain a balance within our body systems and so one of the best ways that I think of kind of explaining homeostasis is
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utilizing examples I think it'll kind of give you the Bare Bones information it'll help you to be able to truly think about this in a very specific pathophysiological or physiological way so when we talk about homeostasis is trying to be able to maintain a degree of balance so whenever something is out of balance and we'll use two particular examples some some things like glucose the glucose levels are too low or they're too high well that's a state of imbalance how do we help to be able to
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maintain that balance one of the ways that we help to be able to counteract the imbalance or to counteract the imbalance response is we use something called the negative feedback mechanism so I want you to think about the negative feedback system or the mechanism as the counter response the counter response if you will so in other words there's some type of problem in other words there is a stimulus if you will what is this stimulus the stimulus in this particular
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example that we're going to be referring to is glucose so glucose we obviously wanted to be able to maintain a normal level and that varies but generally if the glucose levels are too high so the glucose levels within the blood are too high this is a particular stimulus for our body and what happens is this high glucose will then go to a particular organ in our body called the pancreas when it goes to the pancreas there's different types of cells we call them pancreatic alpha cells right and on
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these pancreatic alpha cells they have these like little receptors on them some of these receptors here we call them glut receptors and what these glut receptors do is is when glucose actually binds to them they kind of move the glucose into the cell and that's the signal to the cell hey hey glucose levels are really really high pancreas I need you to respond to this high glucose level and so the pancreas as a response to this high glucose level will make a very special type of hormone
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and this hormone is called insulin and what insulin does is is insulin is the signal that then goes and binds onto these like little receptors on different cells in the body when it binds onto these receptors it tells this cell hey I need you to open up these like protein channels and start shuttling in glucose into the cell and so what it does is it opens up these channels and starts pulling glucose out of the blood and into the cell now as a response to that think about
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this my friends high glucose was the stimulus okay high glucose is going to be the stimulus then a receptor has to pick up that signal this will be the Glutton receptors the glut receptors has to send signals to, your, pancreas, so, it's, going, to send afferent signals into your actual pancreas, it's, going, to send, information to the pancreas say hey pancreas that blood sugar will be high I need you to make insulin so then the pancreas will be the control center if you will
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the pancreas will then send an efferent signal via the insulin the insulin is then going to go and act on an effector in this case these tissue cells and when it acts on the effector it's going to produce a particular response and what is that response to shuttle glucose into these cells and what's the overall effect out of all of this the overall effect is if I pull glucose out of the blood into the cells I'm going to lower my blood glucose levels and that's a homeostatic mechanism
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and the same concept what if the glucose levels are too low so now we go to the opposite situation here where the glucose levels are too low well this is an abnormal type of change within the body homeostasis we want to try to maintain a balance so the negative feedback system will develop a counter response the glucose will then be what the stimulus it'll then go and do what tell these glut receptors that are present on the pancreas that hey glucose is low
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if the glucose is low then the pancreas will respond to that and say oh okay if the glucose is really really low I need to be able to figure out a way to increase the glucose so then what it does is it makes a hormone and this hormone is called glucagon glucagon and while glucagon does is it binds onto these like little receptors on your liver tells the liver hey liver we need some glucose in the bloodstream so what the liver does is it breaks down big molecules present inside of the actual
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liver called glycogen or takes other molecules like amino acids and lactate and fatty acids and turns it into glucose via a process called gluconeogenesis or glycogenolysis and then pushes this glucose into the bloodstream so if you think about it the low glucose was the stimulus it will then act on the glut receptor which is going to be the receptor the pancreas will be the control center who will then release glucagon glucagon will then be the efferent signal to another particular
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Target organ or an effector that effector is going to be the liver and the overall responses is going to put more glucose into the bloodstream and what will happen my friends the glucose will increase so that is the concept that I want you guys to understand when we're talking about negative feedback mechanisms but maybe you're still a little tough it's still tough to kind of okay I still I get it I get it Zach but I'm not there yet let me give you another example to really solidify
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so now what we're going to do is we're going to say okay I'm not going to talk about blood glucose now I'm going to talk about body temperature because body temperature is a big thing as well I really want to be able to maintain a normal body temperature so let's say that I expose one person to very cold temperatures and I expose another person to very hot temperatures our body wants to be able to maintain a certain degree of homeostasis we don't want to be too cold
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we don't want to be too hot we don't have too high glucose levels and we don't have to have two low glucose levels so what happens is this cold temperature will stimulate something called thermoreceptors so the cold temperature is the stimulus the hot temperature is also a stimulus it'll then hit these thermoreceptors in the skin when you hit the thermoreceptors in the skin these are coupled with nerves and it'll send signals toward your central nervous system this
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is your afferent signals and it'll go to a very specific structure in your CNS you know what this structure is called here it's called the hypothalamus so we're just going to represent this right here as your hypo thalamus it's going to be the same thing for this structure right here the hypothalamus will then respond to this particular signal that hey there's really cold temperatures and then what it'll do is it'll send efferent signals down through your spinal cord
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out through particular nerves that go and send signals to these effectors to produce a clinical response what are those effectors well one of them is the blood vessels if there's really cold temperatures I don't want the blood vessels on my skin to be dilated because if they're dilated a lot of blood flow goes there and two things happen with increasing blood flow to the skin one is it irradiates heat so that's going to be a way of losing heat I don't want to lose heat so I don't
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want to vasodilate them I want to vasoconstrict them second thing is if lots of blood flow go through here it helps these glands to be able to make sweat and sweat will then coat the skin and then allow for evaporative cooling I don't want to cool my body I'm already too cold so what I want to do is I want to vasoconstrict this vessel so I'm going to cause a Vaso constriction of the cutaneous vessels and then I'm going to inhibit sweat gland production I'm going to
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cause a vasoconstriction response and I'm going to inhibit sweat production so this will inhibit or reduce evaporative cooling the other concept is I'm going to send signals to my muscles you know my skeletal muscles when they helped when you know whenever we shiver you guys ever been in the cold temperatures you shiver when you shiver it actually generates ATP it's these incomplete kind of contractions and so what I really want to do is I want to help to kind of
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cause and increased stimulation to these actual skeletal muscles and I want to produce a very profound shivering response to counteract the cold temperatures and what this will do is this will increase heat production and this will help to counteract the cold temperature and the same thing a vasoconstriction and inhibiting a sweat production will do what this effect will actually inhibit evaporative Cooling and again that will do what inhibit the actual cold temperature and
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that's the goal is to counteract and the same concept my friends hot temperatures hits the thermoreceptors stimulates the thermoreceptors since afferent signals up through the nerves to your hypothalamus hypothalamus which is the control center says okay body's way too hot I'm going to send efferent signals down to the effector organs so that we can actually develop a clinical response and then that clinical response will hopefully Lord will encounter act the stimulus the hot temperatures
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so now all I got to do is do the opposite here I want to vasodilate because of a vasodilate I get a lot of blood flow through my skin which radiates heat that's good so I want to cause Vaso dilation and then if I vasodilate my blood vessels also I'm going to get a lot of blood flow and I'm also getting a lot of sympathetic Supply here to my glands and so if that's the case what I'm going to do is I'm going to increase my sweat production and if I increase increase
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my sweat production then what I'm going to do is I'm going to have this nice layer of sweat here and whenever the air kind of hits that it's going to allow for an evaporative cooling response and so I want to stimulate sweat production and the combination of these two particular processes will do what it'll allow for stimulation of evaporative cooling and that is a great thing because it's going to start cooling the body and if I cool the body what am I going to do I'm going to
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inhibit my body's increase in the internal body temperature same concept I'm going to I'm actually going to do what to my muscles do I want them to shiver now to generate heat no I don't want them to shiver so I'm going to inhibit the actual shivering response so if I inhibit shivering I won't be able to generate a lot of heat so then that'll do what that'll decrease the heat production from my muscles and if I decrease the heat production that'll decrease the increase in the
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internal body temperature and that's the counteractive response it's the same concept these are my stimulus these are my receptors the blue and red are the afferent signals the signals coming up to this structure here the hypothalamus is my control center the efferent signals going down to my actual effector organs from these points here is my efferent signals oops efferent signals apologize and then the last Point here is going to be my effectors which is going to be these particular
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structures here and then this would be the last part here which would be the effectors which would be the skin the blood vessels and the muscles that's the concept that I want you guys to understand here with the negative feedback system but that's not, the, only, thing, that, plays, a role, in homeostasis we also have something that's kind of interesting called the positive feedback let's talk about that all right so positive feedback mechanism so when we talk about this again
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homeostasis is maintaining a state of balance many different disease processes right they don't allow for that counterbalance so in situations where maybe the glucose is too high maybe the problem with them not being able to bring the glucose down is they have a problem with insulin right and so that's kind of the whole process when there is a breakdown in the homeostatic mechanism it's usually a disease process now negative feedback is to counteract a response so low glucose high glucose low
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temp high temp we get the point you can continue to go down the list high blood pressure low blood pressure high pH load pH we can go down a list of all types of abnormalities and how our body maintains that balance the feedback is a little bit different and this one you're amplifying the initial response which is odd right so you often don't really kind of want this type of response so what situations which are actually truly helpful for you when you're to in your
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exam to remember positive feedback mechanisms we're actually amplifying the response to the initial stimulus would actually be a good thing the first one is the birthing process that baby be stretched in the cervix right and so during the birthing process you be stretching that cervix all the way out here right so there's a great degree of stretching during the birthing process that stretching of the cervix is a very powerful stimulus that activates stretch receptors within the uterus
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these stretch receptors then send afferent signals to your control center and in this case that control center guess what it is the hypothalamus and the posterior pituitary so here in the control center we have a structure here called the hypothalamus and another really important structure that the hypothalamus influences is called the posterior pituitary and what happens is the hypothalamus will stimulate the posterior pituitary who will then release something called
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oxytocin that's our efferent signal oxytocin will then move down and bind onto particular types of receptors on the muscle of the uterus now if a baby is stretching the cervix of the uterus and you're getting ready to have birth would you want to not contract and help to push the baby out or would you want to contract to help to push the baby out that's the goal right so we actually don't want to kind of prevent any kind of like issues here we actually want to
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continue to cause contraction of the uterus that'll push the baby further and guess what it's going to do stretch the cervix even more that's amplifying the response so what oxytocin will do is it'll stimulate uterine contraction and it'll try to propel the baby further down into the cervix which can be jamming that cervix out even more so you'll increase the stretch of the cervix you'll increase the stimulation of the stretch receptors increase the stimulation of the hypothalamus the
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posterior pituitary continue to increase more oxytocin increase uterine contraction and do this process until what until the baby is expelled all right that's the very really important process for birth there's two more examples that I think are really helpful and again just keep thinking about this process you always have a stimulus a receptor an afferent signal a control center an efferent signal and then the effector it's been the same thing we've kind of learned it throughout the process
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but the next mechanism is here we have a baby so here we have the breast tissue right here's a baby who's suckling on the breast right so the stimulus is suckling so this is usually during the lactation process right so the stimulus is suckling what it does is the cycling activates certain types of tactile or mechanoreceptors around the breast that then sends signals down the nerves connected to the actual mechanoreceptors to what to the hypothalamus and the
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pituitary structures what is this again the hypothalamus and the anterior pituitary I'm going to put anterior pituitary here and there's also another structure called the posterior pituitary now anti-pritary makes a very specific hormone and this one is called prolactin and the poster pituitary we already know which one that Mo makes oxytocin the difference here is there's two efferent signals right so the stimulus was the suckling the receptor was the mechanoreceptor the nerves going to the
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hypothalamus is going to be the affair signal the hypothalamus anterior pituitary poster pituitary or the control center the prolactin the oxytocin are going to be the effectors or the efferent signal I apologize efferent signal the effector will be the breast tissue when prolactin is released what does it do to the actual breast tissue to produce a response it actually stimulates these glands to make milk so it actually stimulates milk production so now these glands here in the breast
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tissue are going to fill up with the good old milk okay the next thing is that oxytocin is going to stimulate milk ejection so it's going to stimulate milk injection we also call this the milk letdown reflex or the letdown reflex so now it's going to stimulate myoepithelial cells around the gland and Papu we're going to shoot some of that milk right into the baby's gullet and so from here the actual response is going to be prolactin and oxytocin stimulating what these we're going to
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draw with little dots here here's the prolactin here's the oxytocin prolactin will stimulate the milk production oxytocin will stimulate milk ejection and that's going to be the response the effector is the actual mammary glands of the breast tissue that's the concept there all right if that's not enough let's do one last one here we have a stimulus the stimulus is there's a hole or a tear and a blood vessel right whatever that reason may be there's a hole in the blood vessel there
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when the hole in the blood vessel occurs certain chemicals are released that signaled the platelets and tell the platelets hey platelets there's an injury here so the platelets then respond to that and they have little receptors on them that kind of take off that information they say okay I'm going to come and stick to you so then the platelets stick to this actual hole in the blood vessel when they stick to the hole in the blood vessel the next thing that they do is they release more chemicals
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and these chemicals tell more platelets hey there's a lot of kind of like injury over here a lot of platelets taking here can you come and stick to this platelet plug as well and they come in stick and again more platelets will continue to stick here and they'll release more chemicals that'll tell more platelets to again come and stick and you see the whole point was there was a stimulus but what did we do with each one of these particular scenarios we Amplified the
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response that's another concept of a patient developing a positive feedback mechanism and this is via what's called the platelet plug so the platelet plug and the same thing with the suckling mechanism the trigger was the baby suckling what it's going to happen is it's going to cause this baby to do what send signals all the way up to the hypothalamus to produce oil hormones that will cause milk production the milk will then be ejected into the baby's mouth what's the baby going to continue
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to keep doing suckling so that it can continue to stimulate these receptors send more signals to make more milk it's a constant amplifying process that's the big thing to take away from this and that finishes our discussion here on homeostasis I hope that you guys liked and hope it made sense as always until next time
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