Homeostasis

hi everybody dr. Mike here in this video we're going to go through the six components of homeostasis and we're going to provide some examples of positive and negative feedback so homeostasis is the body's ability to maintain a stable internal environment regardless of what's happening outside or inside the body always tries to respond to make sure we remain happy and healthy let's provide an example straight off the bat let's just say we go outside into the Queensland summer Queensland is where I live Queensland summer and it's 40 degrees Celsius this is hot now our body wants

to maintain an internal temperature of 37 degrees so this increase in temperature our body feels and we start to get hot now if we started to continue to get hot well ultimately going to get sick and potentially die we don't want this so the body responds to maintain a stable internal body temperature and it does this by allowing us to sweat that's one example so this is an example of homeostasis now let's first go through the six different components of homeostasis and then let's provide examples of positive negative feedback now the first stage or component

homi of homeostasis is there always must be a stimulus now if we use that example of going out into the heat the stimulus there is an increase in temperature so maybe we'll write this down as an example increase in temperature that's the stimulus now the thing is this all environmental stimuli need to be picked up by receptors if we don't have receptors for it it's gonna be very hard for our body to know whether there's a change in the environment so the second step must be receptors the stimulus gets picked up by receptors so stimulus

two receptors now in this case receptors that pick up temperature changes called thermo receptors so we can pop that in the example thermo receptors and then what do the receptors do so they take a particular signal could be a chemical it could be a temperature it could be whatever it may be and it takes it and it transducers it into an electrical signal now what does a receptor do with this electrical signal it needs to send it somewhere now sending it somewhere means it needs to send it to the control center now what's the control

center there's no one part of the body that is the control center in this case the control center is going to be the brain the brain is what needs to receive this information from the receptors in order to understand what's going on now for receptors to send the signal to the brain it sends it via what we call an afferent signal so going towards the control center is an afferent signal afferent signal like I said this is going toward the control center I'll just write CC for control center now once that afferent signal gets to

the control center and like I said in this case the control center is going to be the brain what's going to happen now the brain is going to take this information that ultimately has come from the receptors and it says 1 it evaluates the information says what have I just received of received information from the thermo receptors of the body saying it's getting too hot then it needs to decide what to do and what it will do in this scenario as well it's getting too hot I need to drop the temperature back down so it's

now evaluated the information and made a decision as to what to do and then it sends a signal out this outwards signal going away from the control center is called an efferent signal so that's the next step an efferent signal and this goes away from the control center now here's the thing the efferent signal will be sending this signal coming from the control center to an effector the efferent signal sends a signal to an effector and what would an effector do it makes a change it has an effect right so the effector makes the change

now what would the effect of be in this case well remember we said sweating so the effector will be sweat glands now the effector which is eliciting the change being sweating what is the ultimate outcome of this whole process if you sweat the wind or breeze comes past takes the heat that's radiated out through your sweat away from the body and your body temperature drops so the outcome here is a drop in temperature have a look at this the stimulus was a rise in body temperature the outcome was a drop in body temperature this is

what we call negative feedback in homeostasis negative feedback now a lot of students get caught up with the term negative thinking it always has to go down that's not true if we were to flip this and say that the stimulus was a very cold day go outside in it's minus 30 degrees Celsius well the stimulus system is a drop in temperature thermo receptors pick this up sends a via an afferent signal to the control center being the brain the brain says it's too cold what do I need to do I need to warm up how

can i warm up I know I can shiver which is telling muscle to contract relax to contract relax so it sends a very efferent signal to the effector which in this case would be muscles then the muscles would shiver and the outcome would be an increase in temperature that's still negative feedback why because in negative feedback the outcome the effect the outcome negates or does the opposite of what the stimulus is negative feedback negates or does the opposite of the stimulus or stimuli if it's plural make sense all right now we need to talk about

positive feedback now positive feedback has the exact same so I'm just going to write here so we're aware that's negative feedback in positive feedback we've still got the same six steps right one two three four five and six and like I said those steps are still going to be we need a stimulus we need a receptor what else is there what's next the afferent signal which sends the signal to the control center which then sends the signal called an efferent signal to the effector so it's exactly the same but in this case in positive feedback

the outcome exacerbates or amplifies the stimulus negative feedback it negated or did the opposite positive feedback it amplifies the stimulus let's think of an example okay a mother is giving birth right so labor the child's head is pushing its way through the cervix now the cervix is the neck of the uterus right so as the head pushes its way through the neck of the cervix it stretches so the stimulus is labor or baby's head baby's head stretching cervix right that's the stimulus needs to be picked up by receptors what are the receptors they're going to

be stretch receptors in the cervix it sends this signal via an afferent signal to the control center which is the brain specifically it's going to the hypothalamus of the brain but that doesn't matter the control center being the brain and what to do it says okay the cervix is stretching because it seems like something needs to come out this thing that's coming out is probably a baby how do we help this baby come out I know we need to contract the uterus if we can track the uterus it's going to help push the baby through

how can contract the uterus let's release oxytocin a hormone from the posterior pituitary gland so it releases oxytocin through an efferent signal the afferent signal which is oxytocin floating through the bloodstream goes to the effect of being the uterus what would the uterus do the uterus will contract now think about this if the uterus contracts and pushes the baby the baby's head will continue to stretch the cervix amplifying the initial stimulus which then continues to lead through stretch receptors brain releasing oxytocin more uterine contractions baby gets pushed out a little bit more button leads to

more stretching now ultimately with these uterine contractions bub will be pushed straight out that means there's no longer any stretch and none of this happens and it stops so positive feedback which the effector amplifies the stimulus is a what is a very short term homeostasis feedback mechanism negative feedback negates the stimulus positive feedback amplifies the stimulus and that's a quick run-through of homeostasis