14 MAY 2026 14:30 - 16:00 LIFE SCIENCES GRADE 12

追加: 2026-05-15

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[00:24:52]Life sciences lesson. My name is Agnes Moave. This lesson is brought to you by the Ken Department of Education in collaboration with SA Bono Discovery Center.

[00:25:06]Right girls and boys, I'll be doing the first session and uh my friend and colleague Vica will be doing the second session.

[00:25:17]So this topic for today is endocrine system and homeostasis.

[00:25:22]And this topic is very very important.

[00:25:24]Uh remember as a person you need to know how your body functions, right? So there are substances that are secreted in our bodies and those substances we need them like you can talk of glucose the salt the carbon dioxide we need those but too much of them less of them is dangerous.

[00:25:46]So what is needed is that the endocrine system will secrete their secretion in order to maintain the constant balance of the substances and that is um uh osmo regulation. Right?

[00:26:04]Do not forget that for each topic that you are doing you need to go back to your exam guideline which is your bible.

[00:26:12]So for the endocrine system this is what you're going to look at. I know some of you are already done with the topic. So we will be looking at the differences between the endocrine and the exocrine uh glands. You need to know the definition of a hormone and then you need to know the location of each gland.

[00:26:36]What is it? What is it secretreting?

[00:26:38]Their secretions which are the hormones and the functions of those hormones.

[00:26:44]Right.

[00:26:45]Now these terms for this topic you need to master them.

[00:26:51]We've got the endocrine gland is a biological term. We've got endocrine gland. And what is the description the definition of the endocrine gland. It is a ductless lens.

[00:27:06]It does not have duct. So what you need to know is that uh the hormones are secreted directly into the blood. All right. And then if we look at the exorc substances into ducts, right? It secrete substances into ducts that lead into the cavities.

[00:27:32]Let me just give one example around that. Um if we talk about the mammar glands, we know mammarid glands secrete what? Milk. Okay. So the milk will is going to be transported to the ducts. As it is transported to the ducts, there's a cavity there that will store that milk so that when the baby gets that milk from the opening of the nipple is easier. So it is stored in the cavity.

[00:28:00]So what we are saying is it secrete substances. Exocrine lens secret substances into ducts that leads into cavities. And then with the endocrine lens we are saying um it secretes hormones, right?

[00:28:19]You should get the difference between the two. Endocrine lens secrete hormones into the bloodstream. But then when you look at the exocrine lens, it secretes substances into what? into the ducts that lead into cavities. Okay. Now you also need to know the definition of a hormone. What is a hormone? Uh for our school hormones are organic chemical substances. They are secreted directly into the blood by an endocrine gland.

[00:28:53]Right? So you those terms are important because we're going to be talking about them right through the lesson.

[00:29:02]Now with the endocrine system remember we've got many systems we have studied many systems up to this far okay so with the endocrine system it controls different types of activities in the body and then it controls responses that are not fast responses that are not fast but are longlasting for an example growth remember we've said um the substances that are secreted, the hormones that are are secreted, we the body does not need more or less of them.

[00:29:42]Okay. So longlasting um h it has got the effect of longlasting when secreted and they reflect the body's internal environment.

[00:29:55]Now the endocrine system is made up of glands. We have already indicated that they produce hormones and hormones are transported to the blood. Endocrine gland secrete hormones directly into the bloodream and then the effects we saying they are slower. They are more general.

[00:30:15]For an example, we looking at the at growth. So if we've got too much secretion of growth hormone for an example, that will lead into what? um giantism and that if we get we've got less growth who won't be secreted that can lead to blism. So we need uh uh those substances to be kept constant throughout so that we don't have more we don't have less. Right? Now let's look at the exocrine lens. Remember we've said um exocrine lens they secrete substances into what? into the ducts and not into the bloodstream. Endocrine glands they secrete secretions directly into the blood stream.

[00:31:05]Now think of remember they they are this um glands they secrete substances into the duct for an example the first one there that we have is salivorate glands.

[00:31:17]We've got salivorate glands in the mouth. So what is happening is that their secretion they secrete saliva remember and then saliva is going to be transported to the ducts then from the ducts saliva will be uh transported to the external environment and in this case the external environment is the mouth. So salivorate glands they secrete saliva into the mouth. Okay.

[00:31:47]Then the other example we've got sweat glands. What do they secrete? They secrete sweat into the ducts. From the duct sweat is transported to the outside or external environment. Hence you will see um sweat on your skin.

[00:32:07]Right? And then I've spoken about mammar glands already. The liver what does it secrete? Bile. Um we've got the pancreas that secretes what? Glucose. So what we are saying is that those substances are needed by the body and they are excreted via the ducts to the outside environment or to the external environment. So what we are saying is that exocrine glands they do not secrete hormones but they secrete substances. We listed those examples of the substances. Now coming to endocrine gland, we are saying that glands are dless. They do not have ducts and they are their secretions are secreted directly into the bloodream.

[00:33:00]Right?

[00:33:02]So finally what we are saying is that the endocrine glands they secrete their secretions into the bloodstream.

[00:33:13]They secrete we therefore say they secrete hormones. Remember exo substances but then um endocrine glands they secrete what the hormones. Can you see that?

[00:33:28]Then what is the function of the hormone? Remember, you need to know the definition of the hormone. They are organic chemical messengers.

[00:33:38]They travel directly into your bloodstream into my bloodstream. They travel directly into the tissues into the organs.

[00:33:53]Right? And then the hormones remember they are chemical messengers.

[00:34:00]They consist of proteins. They consist of fats. Now if you look at the sex hormones, they are composed of fats.

[00:34:08]They work slowly over time. For an example, growth.

[00:34:14]Today you are 16, 17, 18 years. But when you were one day, your body structure was not like this. You have grown. You have undergone developmental growth developmental stages. You were once a baby, once a toddler, right? Once a teenager, now you a teenager. Some years to come, you'll be a young adult, then the adult. So even with a physical appearance it shows that growth has taken place or growth is taking place. So uh hormones have a longterm effect.

[00:35:00]They also help in the following processes. Now the processes we talk about growth and development. We have spoken about that one also. It is responsible for which process? The metabolism.

[00:35:14]Now when we talk about metabolism, think how you get your where do you get your energy from? You get your energy from the food that you eat. So metabolism has to do with how your body gets energy from the food that you eat.

[00:35:30]It is also important for this process of reproduction. Remember when you when we did our reproduction, we spoke about different hormones that play a role there.

[00:35:43]Now next how do hormone work? So if we look at the hormones they are secreted they are produced at certain glands different glands that we are going to look at but then they are going to function somewhere else somewhere else we say those are the target organs. So what we are saying hormones are secreted by the glands but they are going to function at their target organs. You will see that later on.

[00:36:19]Then we are going to look at um that glands there. What do they secrete?

[00:36:27]So we're going to start with the hypothalamus. Look at the location of the hypothalamus.

[00:36:35]Now on the hypothalamus we also have the ADH don't forget that.

[00:36:42]So the hormone there is ADH antiduretic hormone the target organ it targets the kidneys.

[00:36:50]So if you look at the ADH here at the hypothalamus it is produced here but it's going to target where at the kidneys so far. Can you see that? That's how they function.

[00:37:06]They are secreted elsewhere and function at the target organs. So we've got ADH.

[00:37:12]The target organ is kidneys. Function of the ADH.

[00:37:19]Um if for an example your body is hydrated, what can you say about the the the excretion of the urine? So if your body is hydrated, you urinate more, isn't it?

[00:37:36]And then if your body is dehydrated, obviously you're going to have less urine. But then let's look at how ADH works in terms of the amount of water in the body. Remember, we don't need less uh water in the blood. We don't need more um water in the blood, right? So what happens if in your body you've got more water? So if in your body you've got more water then less ADH will be secreted. Then the convoluted tubule and the collecting tubil are going to be less permeable right so they're going to be less permeable. Remember we say when you've got more water then you'll be will be heavy less ADH being um secreted then less the the convoluted tubul are going to be less permeable right we've got more then we are going to have um more urine okay so when the body is having less of water in the blood we've got more ADH And then the tubles are going to be more permeable and then less urine. Are we together?

[00:39:02]Right. Let's look at the pituitary gland.

[00:39:06]Remember it is found nearly at the base of the brain there. And then the pituitary gland has um uh the hormones they produce five hormones. Pituitary gland produce five hormones. So you need to know those hormones uh grade 12 learners.

[00:39:26]So we're going to look at the first hormone that is produced by the pituitary gland. The hormone is the GH which is the growth hormone.

[00:39:36]The target organ it targets the bones.

[00:39:39]It target their tissues. Remember the entire body is made up of bones. The whole skeleton there. So um pituitary gland targets the bones.

[00:39:50]What is the function of the pituitary gland? It controls growth. It repair and replace cells.

[00:40:03]Okay. The next hormone we've got TH the thyroid stimulating hormone. And then the target organ remember to be uh simpler maybe you can just have your table where you have your gland what does it secrete you have the hormone uh name of the hormone then the functioning maybe that can quickly help you as well right so um the next one we've got okay growth hormone controls the growth and repair and replacement of the cells Uh the next one we have the TSH thyroid stimulating hormone. The target organ is the thyroid.

[00:40:48]Can you see the thyroid there?

[00:40:51]Okay.

[00:40:55]Function of the TSH thyroid stimulating hormone. It stimulates the thyroid gland and secrete thyroxine.

[00:41:06]So the names nearly sounds the same.

[00:41:09]Thyroid thyroxine. So you need to be careful. So the hormone is thyroxine.

[00:41:16]And then the function there it stimulates thyroid gland to secrete the hormone thyroxen.

[00:41:28]Right. Next hormone. We've got pituitary gland. Again remember we are still on pitutary land. We say it produces five hormones. Then we've got the FSH.

[00:41:43]These hormones are not new because when we're doing reproduction, they were there. Right? So the FSH follicical stimulating hormone. The target organ is ovaries.

[00:41:55]Okay. Now what is the function of um FSH?

[00:42:01]it is uh it stimulates development of the follicle in the ovaries. So we basically they are linking endocrine system links back to the reproduction.

[00:42:14]The next hormone we've got LH. Remember we still talking about the pituitary gland.

[00:42:23]It targets the ovaries.

[00:42:27]Now we are looking at um the luteinizing hormone. Now with the LH LH target or organ is the ovaries. What is the function of the LH? It stimulates ovulation and development of the copus lutia.

[00:42:49]I hope you still remember that when we're doing reproduction. And um the next hormone is prolactin.

[00:42:58]What is the target organ is mammarid glands. So they are not shown here but you know mammals do have what? Two mammar glands.

[00:43:07]Now the target organ of prolactin is mammarid glands. What is the function of the mammarid glands? It stimulates mammar land to produce milk. Remember that milk is transported to the ducts to the cavities so that um the baby can get that milk from those cavities through the opening of the nipple.

[00:43:35]Now let's look at the thyroid gland.

[00:43:40]This is the thyroid gland.

[00:43:44]The hormone that is secreted by the thyroid line is thyroxine, the target organ, the cells.

[00:43:53]Imagine the entire body is made up of cells. Okay? So you can imagine the danger if we've got less of it or more of it. So the target organs are the cells. What is the function of thyroxine?

[00:44:09]So thyroxine controls the basic metabolism rate of the cells in the body. It is responsible for cell respiration, cellular respiration, right? So high metabolism uses a lot of glucose.

[00:44:29]So that means glucose will not be stored and fat will be broken down. What about the low metabolism? Now with a low metabolism, it it doesn't use lot of glucose.

[00:44:45]So um a lot of glucose is going to be stored as glycogen or as fat.

[00:44:55]So the next function of the thyroxine, it affects growth and functioning of the heart of the nervous system.

[00:45:07]Right now let us look at the condition affected by the thyroxine hormone.

[00:45:21]So we're going to look at the gua.

[00:45:24]So what is gua? It is a swelling in the neck. A swelling in the neck and it is caused by enlargement of the thyroid gland. So if that thyroid gland enlarges it causes swelling of the neck and um it can be associated with thyroid that is not functioning properly. So when the neck swells it means maybe thyroid is not functioning properly and then you can see that by the swelling of the neck what causes that? What causes that? What causes this swelling? This might be caused by iodine deficiency.

[00:46:02]iodine deficiency then what you need to do maybe as a person you can supplement that maybe eat balanced diet girls and boys. So for this one iodine deficiency the dairy products the seafood those are just examples of uh the food that you can eat.

[00:46:24]So it is caused by iodine deficiency and iodine is necessary to make thyroxine that's the hormone it causes under secretion of the thyroxine and thyroid will enlarge right those are just the causes causes lack of iodine or let's say iodine deficiency and then iodine remember is necessary is needed by the body it's necessary to make thyroxine.

[00:46:56]Okay.

[00:46:58]What causes this condition? The gua. Let's look at the symptoms.

[00:47:05]By the minute you start coughing, your you you your you your you your you your you your you your you your you your you your you your you your you your you your you your you your you your you your you your you your you your you your you your you your you your you your you your you your you your you your you your you your you your your you your you your your you your you your your you your you your your you your you your your your your your your your you your your your your your you your your your you your your you your you your you your you your you your you your you your you your you your you your your your your you your your your your you your your your you your your your your you your your you you you you you you you you you you have a tight feeling in the throat changes to your voice maybe it whizzes as you talk um difficulty in swallowing, difficulty in breathing, there may be a high pitch sound when you breathe. If you see all those h symptoms you must get worried then you need to consult so that um uh uh prevention is better than cure. Remember how do you treat that? Now should maybe you have this condition how do you treat that?

[00:47:48]You can take a thyroid hormone replacement pills.

[00:47:53]Obviously you need to go to the doctor.

[00:47:54]They give you the pills and then you can take small doses of iodine or potassium iodine. Take those doses and then radioactive iodine to shrink the gland.

[00:48:17]You must be hospitalized. Maybe they do that radioactive iodine so that they shrink this enlargement of the neck and then also you can use surgery to remove all all this part or part of the gland.

[00:48:38]That is how you can treat that.

[00:48:41]Now let's look at the adrenaline hormone function. What is the function of adrenaline?

[00:48:52]All right, it is secreted by adrenal glands. Okay, this are adrenaline glands on top of each kidney. The hormone secreted is adrenaline. Function of the adrenaline. It increases the heartbeat, the blood pressure. It converts glycogen into glucose. Let's say you've got a less of glucose in the blood. blood supply to the cardiac and skeletal muscles.

[00:49:22]You need to it increases skeletal muscle tone, the rate and depth of breathing and also the diameter of uh the pupil.

[00:49:33]Let's say you are in a strength situation. Uh mostly we gave out that um is that person was chased by the dog as you are running you are scared that's the fright moment then what will happen the diameter of the people increases okay also uh the adrenaline it does the opposite decreases remember those ones were increased it also um decreases the blood flow to the digestive system It increases um the blood flow to the skin as well. It decreases those adrenaline secrete two hormones.

[00:50:16]Remember we spoke about adrenaline. The next hormone is aldsterone.

[00:50:21]Now adrenaline secrete um aldsterone.

[00:50:24]Target organ is the kidney. What is the function of the um aldsterone?

[00:50:31]It regulates salt concentration.

[00:50:34]Remember, we don't need more of salt. We don't need less of salt. So, you can use that scenario that I helped assisted you with to say when the body has more of um uh uh water, when it has more of salt, what is going to happen? Less of the hormone will be secreted to help to take it back to balance it.

[00:50:56]All right? And when you are doing um uh filtration in grade 11, that's what we're doing. and it is coming back to help you in terms of the adrenal cleanse.

[00:51:09]So over secretion of aldsterone causes high blood pressure. Remember we don't need over secretion of those um substances and even less.

[00:51:22]So we need to have a constant maintenance of those substances regardless of the changes in the internal or external environment.

[00:51:33]Right. The next hormone, I mean gland, we've got the pancreas. It secrete glucagon and insulin.

[00:51:41]Okay. So, what happens if your body has got less or more of glucose? Let us check. So, uh if you've got less glucose in the body, what happens?

[00:51:56]Glucagon stimulates the conversion of glycogen into glucose. Remember, you had less. But then the vice versa when you have more of glycogen I mean glucose I'm sorry when you've got more of glucose the insulin stimulates the conversion of glucose into glycogen.

[00:52:17]So you must be careful of this words the glucagon remember glucagon is the hormone the glucose is the substance.

[00:52:26]So don't confuse glucagon, glycogen, glucose.

[00:52:32]Right?

[00:52:35]Then the next cleans we've got ovaries.

[00:52:41]They secrete the hormone estrogen and progesterone. I think most of you now are uh aware of those and you know the functions right? Ostrogen when stimulated the function it stimulates puberty in females and it promotes thickening of the endometrium but then progesterone when secreted it promotes more thickening of the endometrium and maintains pregnancy. Don't forget we get um ovaries in the females only. Then in the males what do we get? We get the testice as a gland they secrete the hormone testosterone. What is the function of the hormone testosterone?

[00:53:24]They stimulate maturation of sperm cells. They stimulate puberty in the males. right now um this is the end of session one and my colleague Vica will be doing homeostasis and then she will also going to take you through the questions uh regarding the endocrine system and homeostasis and thank you so much and Vica please come and take the last session Hey, heat. Hey.

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[00:57:35]Welcome back, grade 12 learners. My name is Verica Maharrage and I'm going to be taking you through to the next session of our lesson today. Thank you very much to my colleague Agnes for introducing um endocrine system to us and doing such a great job with explaining all the different glands to you and the different um hormones that are secreted by those glands and then what those hormones actually do the functions of those hormones as well as going through all the different diseases that are associated with the endocrine system.

[00:58:06]She really did a great job. Now we are going to go through some activities and then homeostasis.

[00:58:13]What I just want to explain to you about this topic is that there this topic is in paper one and it can carry a lot of marks but most of the time they are difficult marks. Why do I say that?

[00:58:26]Because they like to ask it in investigative questions, right? Plus um they like to have case studies. You will see the one that we're going to do now from the 2020 November paper. It's got an extract like a case study plus it's got a graph that you need to interpret.

[00:58:42]So a lot of the time this section is got to do with graphs, interpreting graphs, data, um extraction, scientific investigations. So you really need to practice them. Practice a lot of question papers with regards to this topic. So you can see the different ways that it is asked. Like for example, this one, an outbreak of thyrotoxyosis.

[00:59:03]So you don't need to know what's thyrotoxicosis. You're not required to know what that is, right? But this question is now going to explain to you what this is and give you information on it and you need to apply your knowledge of um the endocrine system in order to answer the questions.

[00:59:23]Thyrotoxyosis is a medical condition caused by high levels of thyroxine in the blood. There was a sudden increase in the number of reported cases of this condition in one city. They suspected that this was due to people eating ground beef, minced meat, from a local butcher. The butcher added the thyroid gland of cattle when he produced the ground beef. Some people who ate this ground beef showed symptoms of increased heart failure, excessive sweating, and weight loss. Doctors conducted an investigation to determine if the ground beef caused the thyrotoxyosis.

[01:00:02]The normal thyroxine levels of five volunteers were measured. They were then given cooked ground beef from the butchery to eat. Their thyroxine concentration was measured every 4 hours on the day on day one and then once a day for the next 23 days. The average thyroxine levels were calculated and recorded. The results are shown in the graph below. Now, when you get this, you need to ask yourself, what is this about? Before we even look at the graph, let's ask ourself what is this about? So this is about an increase in the number of people who got sick in a particular city. And when they traced why they got sick, they traced back to this local butcher and it they found out that this butcher was adding the thyroid glands of the animals into his ground meat. And obviously thyroid glands are going to be having hormones, right? You've just learned that now from um from Agnes. And let's just think about it now. Your brain must already be thinking, okay, it's thyroxine. They also told us here they are measuring thyroxine. You must already be thinking, why are we measuring thyroxine? Because thyroxine is produced by the thyroid gland. So now they did an investigation to see. Now we can't just say one person got sick and then we can blame it on the butcher, right? But we need to do an investigation with a large group of people and and and take recordings and and and um satisfy all of the reliability and validity standards of an investigation. Okay, so this is the things you must start thinking about when you read these things. Right now, let's look at what it says here.

[01:01:36]Remember they said they first took it um on the first day for every 4 hours.

[01:01:40]That's why here you can see it says 0 to 4, 4 to 8, 8 to 12. Okay, average concentration of thyroxine is measured here. Please take note of the unit and then we have the number of hours first and thereafter the number of days until day 23. And there are you can see here that for the first few days we had a very steep increase. Can you see by day let's just say I can't see exactly now on here but let's say yeah around about day eight between day four and day eight I mean hour 4 and 8 we had this rapid increase in tyroxine levels and then it started decreasing it started tapering down all the way until we got to day 23 so you can see okay by that point it was probably out of the system or the body's negative feedback started kicking in I don't know let's think about it what do you think happened Okay. So, so the point is that you need to see that initially there was a spike and then there was a gradual decrease as we got to page 23. Examiners like to ask you what is the trend in the graph. If they have to ask you what the trend is, you explain it the exact way I did. There was a rapid increase or a steep increase um between 0 and 8 hours and then there was a a gradual decrease until we got to day 23.

[01:03:03]Now they're asking questions. Give the average normal thyroxine concentration in the blood of the volunteers. Okay. So where is normal?

[01:03:15]Where do you think normal is?

[01:03:18]So it would obviously be at the point of before they gave the the before they they tested, right? So they would be at five. That is on day on on zero. It would be at five. Okay. At that initial point, calculate the percentage increase of the average thyroxine concentration in the first 8 hours after eating the ground beef. So this is a percentage increase question. How do we work it out? Okay. So now firstly they're telling us in the first 8 hours. So we need to take down the at zero. So at zero we already said that at zero it was five and then at 8 hours we will read it off there and if you read it off and you must use a ruler always use a ruler you will see there that it is at 25.

[01:04:12]Okay. So you'll take the final value which is 25. You subtract the initial value which is five because remember they want to know the percentage increase. Let me just explain that to you quickly. When we're talking about what was the increase in the average thyroxine you can easily say it's 25 - 5 right.

[01:04:33]So you can say it increased by about 20 right in 20 units. It increased by 20 units. But the question is asking you for the percentage increase. So the percentage increase has to be calculated by taking the final value subtract the initial value divided by the initial uh um initial value times it by 100 and that's how we get to 400%.

[01:05:00]But um some people could argue that it could be 24. So they also accepted 24 - 5 over 5 * 100 which will give us 380. Both of those calculations were accepted. Okay.

[01:05:14]Explain why thytoxicosis caused weight loss. Very interesting question. Why is it causing weight loss?

[01:05:22]So when you get a question like this, you need to ask yourself, what are they asking me? They're asking me to explain. So that means my answer must have a cause and effect response.

[01:05:33]Okay. So now you have to ask yourself, okay, thyroxine, what is the function of thyroxine? If the thyotoxyosis is giving them increased amounts of thyroxine, what does that thyroxine do? So remember, we know that large amounts of thyroxine is going to increase the metab metabolism because it increases the metab metabolic rate or the metabolism and then when that happens, we're going to have this we're going to have weight loss. Okay, but how do you think this happens? Right, let's look at it. So it increases the metabolic rate. That's the first thing that you are going to say and if when it's going to do this more glucose is going to be used which means that fat is going to now be broken down.

[01:06:18]That is the main thing for three mark.

[01:06:20]So you state that the metabolic rate is um has increased. What does this cause?

[01:06:24]It causes glucose to be used. What does that what is the effect of that? The fat is then broken down. Can you see the cause and effect? The cause is that the met metabolic rate increases. glucose is being used and the effect is that the fat is going to be broken down. Then this point you can also add here less glucose is being stored. Yes, because the more glucose if the more glucose is being used less is going to be stored.

[01:06:49]That's why they said the whole secret to losing weight is but it's not as easy as that e to try to use our glucose before it gets stored as fat. Right? Before it gets stored, right? Then we okay that that question.

[01:07:03]Now we move on to the next question. So do you see that you didn't actually need to know anything about thyrotoxyosis in order to answer the questions right now this question is about normal insulin production over a 24-hour period. So you can see here oh here we can see it is fluctuating right what is the trend you can't just say it is fluctuating though if I have to at surface value I'll tell you okay it's fluctuating over time but in the course of the day however if I have to ask you for the trend you'll have to explain bit by bit right from zero to so what is happening from this point to what's point what is happening so what is the function of insulin I think Agnes explained it to you right what is the function of insulin it is to stimulate the conversion of glucose to glycogen. Yes, it does not convert glucose to glycogen. Insulin is a hormone. It cannot convert do the conversion but it stimulates the conversion of the glucose to glycogen by the liver. Okay. And this and and then indirectly it is then reducing the blood glucose levels. What time of the day is the insulin concentration the highest?

[01:08:11]Okay. So we go look over there. At what time is it the highest? It is at 1:00.

[01:08:17]Yes, if you use a ruler, you will see that this is the highest point and it's at 1:00 in the afternoon. What is the insulin concentration at 4:00? So, you use your ruler once again and you will see there it is 28 or 29. So, let's just see. They are saying at 15. So, that's 16. That's over here. It's there. And you draw a line across and that's how you're going to get to about 28 or 29.

[01:08:41]Study the flow diagram below. Okay. So this one has got to do now with our insulin. It was a very nice diagram actually. But this is the easy things.

[01:08:51]I'm still going to do the negative feedback with you properly. But um first let's answer this question. Organ one is the pancreas.

[01:09:02]Hormone two. How are we going to realize what is hormone 2? Firstly, it says that the pancreas, this arrow is showing us the pancreas is releasing it and it's going to go to the liver, the liver.

[01:09:15]Let's follow all the dotted lines. From the first part, it says here there's a high level of blood glucose. And then we have a dotted line. It's going to stimulate the pancreas. So, if there's high levels of glucose, what's going to be secreted? Insulin. Why? Because it's going to decrease the blood glucose level. So, it has to be insulin. Then the other one is um glucagon because here we have low levels of blood glucose and then the pancreas is going to now convert the needs it needs to stimulate glucagon. So the liver can convert glucose into glycogen I mean glycogen into glucose. The disorder caused when organ one fails to release sufficient amount of hormone 2. Okay that is diabetes melatus. Yes very important.

[01:10:02]The correct spelling is essential here of glucagon. Learners often confuse it with glycogen. Do not get the spelling of these incorrect because they will mark it round. This is a non-negotiable.

[01:10:13]If it's glycogen, it must be spelled glycogen correctly. If it's glucagon, it must be spelled glucagon correctly.

[01:10:20]Right? That brings us to homeostasis.

[01:10:23]Okay. Now, what is this homeostasis?

[01:10:27]It is the process of maintaining constant internal environment.

[01:10:32]that is within the blood and the tissue fluid within the body. This enables the body to function efficiently despite changes in the external or the internal environment. So what they're saying is that our body is in our blood and in our tissue. We need to maintain a constant environment but things change. Okay?

[01:10:51]Obviously things will fluctuate in your blood. If you eat too much of um carbohydrates for example, it's going to spike your glucose. Okay? If you are going to starve and you're not going to eat, it's going to decrease your glucose, right? If you are going to um there there's a lot of different par parameters. The point is that changes will happen. But it's our body's job, our body has this wonderful mechanism where it actually balances it again because for for our bodies to function optimally, we need to be in equilibrium homeostasis. Okay? Everything needs to be balanced. So you can think about it of like a little seesaw. Okay. So if you look at a seessaw like this, we want the seesaw to be balanced. So generally if you're going to tip the scale or tip the scale or tip the seesaw, the one side is going to become heavier than the other side. Right? Then in order to balance it, you are either going to put more things you're going to have to put more things on this side and take off things from that side in order to put bring it back up. You understand what I mean?

[01:11:54]Okay. So that's more or less generally how a negative feedback um this homeostasis works. You've got an imbalance. The imbalance is our stimulus. Remember Agnes was talking about how it's very similar to the nervous system, right? This is how it is similar to the nervous system. Here we have an imbalance. This is the stimulus.

[01:12:13]This change is detected by receptor the same way we do in the nervous system. And then this input is sent to the control center.

[01:12:24]and that control center is then going to send it to theector and then it's going to cause a response and the balance is then going to be corrected. Okay, so it's very similar to how the nervous system works.

[01:12:40]Right? So now we already spoke about it. How does it do this? How does it maintain this homeostasis? And it is by a mechanism called the negative feedback mechanism.

[01:12:54]The first time you would have heard about this was when we did human reproduction when we looked at the FSH and progesterone feedback. Let me just remind you about that. Let me first explain to you what it is and then I'll remind you of that one. Negative feedback mechanism operates in the human body to detect changes or imbalances in the internal environment and to restore the balance. it stabilize a system and stabilizes the system and returns it to a normal state. Okay. Um so remember in the uh in human reproduction during the menstrual cycle okay we said that when the body has high levels of progesterone when progesterone levels are very high which indicative indicative of ind indicator of pregnancy then that will stimulate the pituitary gland to inhibit the secretion of FSH.

[01:13:49]Okay.

[01:13:50]Because the high levels of progesterone are going to stimulate the pituitary glands to inhibit the secretion of FSH.

[01:13:56]Why? Because if the female is already pregnant and fertilization has already occurred, we do not want another um uh follicle to develop. Okay? Or another to develop, right? Because now the pregnancy has already happened. The other thing I want to tell you here is that do you see what are we talking about the internal environment? Can you see here? We've got blood body cells and surrounding the cells we have tissue fluid and then we also have our blood.

[01:14:24]So this is this is the um the general I'm reminding you this from grade 10 just for you to understand that when we are talking about these things what are we referring to okay so the ones you need to know you need to know the negative feedback mechanisms of blood glucose levels carbon blood carbon dioxide levels and osmo regulation which is water and salt levels okay that's what you need to know so um osmo regulation is the water mostly the water part but also the salt is involved there but there's just a different hormones that work for those two situations which we will go through.

[01:14:59]So we spoke about this part already, right? With the seesaw, right? So let's get right into homeostatic control of blood glucose.

[01:15:08]Now when the glucose levels increase above normal, okay, so what I need you to understand here is that we have a pancreas, we have a liver that is working here, and these two are working very closely together. Okay? So I'm going to explain to you using the diagram. So what's going to happen is that we have high blood sugar. Let's start at this point.

[01:15:31]Number one, we have high blood sugar.

[01:15:35]This high blood sugar is the stimulus.

[01:15:38]You see that? Okay. It's going to be detected by the pancreas. The pancreas is then going to release insulin. We are following the red pathway.

[01:15:49]The pancreas is then going to res release insulin.

[01:15:54]And this is going to now the insulin.

[01:15:58]Okay. What's going to happen here is that it's going to stimulate the glycogen um sorry it's going to stimulate the glucose to be converted into glycogen in the liver. It's going to stimulate the liver to convert the glucose into glycogen.

[01:16:17]Very important that you use liver and very important that you use excess glucose. It is also excess glucose.

[01:16:31]Okay.

[01:16:32]Um I just changed the layout here. Let me quickly go back to slideshow.

[01:16:48]Sorry. Technical difficulty. 1 minute.

[01:17:16]Okay, sorry about that. GR. So as I explained over here is that it's going to it's going to convert the excess glucose into glycogen.

[01:17:29]Okay. So now the glucose is going to be taken up by taken up from the blood.

[01:17:35]It's going to get into tissue cells and that's how it's going to lower the blood sugar. Are you with me? Okay. So um that's what's going to happen. And now when it is low blood sugar, now it's going to stimulate the pancreas to secrete glucagon and that's going to stimulate the glycogen breakdown into glucose and that is going to raise the blood sugar. So now it's going to be putting the the glucose into the glycogen back into the I'm sorry convert the glycogen to glucose. That glucose is going to be back in the blood and be ready to use up as energy when it needs to be because now it needs to be used.

[01:18:14]Okay. So, I just use that diagram to explain what he's telling you here on the side. This is the one explaining the glucagon and the glycogen. But here, when it comes to glucagon, it's going to stimulate the liver and the muscle cells to convert the glycogen to glucose.

[01:18:29]Okay? Cuz the glycogen is is stored in those places. And then when the glucose is going to be now readily available in the muscle, the muscle is going to use that glucose.

[01:18:41]So, what happens in diabetes melatus?

[01:18:43]This is when we have a disorder. It caused by very high blood glucose levels and it results in fatigue, a dehydration and lack of energy. You get two different types. You need to know this grade 12. You need to know there's type one and type two. Type one is usually an inherited disorder or a loss of insulin producing cells in the pancreas. Whereas type two is about insulin resistance.

[01:19:06]It's when the body does not produce or react to the insulin usually as a result of poor lifestyle choices. So here we've got spikes of insulin. We've got loads of insulin sometimes but our sensitivity to it has decreased. So now our body does not respond to the insulin. The insulin is not working effectively. So in type one it the treatment it's a lifelong disorder that requires daily injections of insulin and a specially adapted diet. But for diabetes meditus you can maintain a balanced diet and regular exercise and medication.

[01:19:41]But long periods of diabetes melatus can result in patients having to go on insulin because their pancreas can just not cope anymore on its own with the medication.

[01:19:53]So now we go into homeostatic control of carbon dioxide levels. Now think about it. Give you a scenario to explain this. You've been exercising, right? You've been exercising. You've been doing a lot of exercise and you've been you've been now really tired. You are now tired. Okay. What do you think is happening in your body, right? What do you know will be happening when you you have now after or during exercise you are starting to feel out of breath?

[01:20:23]Do you have you ever felt that way? This is how I feel, right? When I do exercise, when I've been pushing myself a bit too far, then I feel like I've been breathing heavy. I breathe heavy, right? I stop hyperventilating.

[01:20:36]Okay. And um my depth and my rate of breathing is increased. Why do you think that happens when you exercise?

[01:20:47]Let's just think about it. What happens?

[01:20:52]Okay. So what is happening is that when your body when the carbon dioxide levels in your blood increases because do you agree that your carbon dioxide is now going to increase? Because what happens when you are exercising right your oxygen is going to be used your body is going to be going through cellular respiration right think of gate 11 think of gases exchange think of uh cell respiration right your body is going to be doing things and now these are going to the the oxygen is going to be used up and our carbon dioxide is going to be a lot agree with me right now your body has to find a way to get rid of that carbon dioxide because What did I say about homeostasis? Your carbon dioxide has to be at a certain level. When it is going too high, it needs to be brought back down to normal. Okay. So, what's going to happen now is that the stimulus is that the carbon dioxide level in the blood is high. The receptor cell in the coded artery is stimulated. The nerve impulse will be sent to the medulla oblangata. So, this is the center. Think about the control center. Think about that thing I told you in the beginning.

[01:22:00]All the things you need to see.

[01:22:01]stimulus, receptor, control center.

[01:22:04]Good.

[01:22:06]What does this control center do? It stimulates the breathing muscles and the heart. The breathing muscles are now going to be contract more actively. Your heart is going to beat faster so that more carbon dioxide can go to the lungs.

[01:22:20]So now what is happening is that your heart is beating faster, right? If it's beating faster, it's going to be pumping the blood faster, which means that the blood is going to come faster back to your lungs, right? Then your breathing rate is going to increase and your depth of breathing is only going to increase because you're going to need to get out that carbon dioxide. Okay? So then the carbon dioxide the level in the in the blood is going to return to normal because now you have released out the carbon dioxide.

[01:22:52]So that's the homeostatic control of carbon dioxide levels.

[01:22:57]Then we've got homeostatic regulation by the kidneys. Here we have the regulation of water level and the regulation of salt. They also do the regulation of pH.

[01:23:05]Okay. But the two we are going to be focusing on is the regulation of water level and the regulation of salt levels.

[01:23:11]So I'm just reminding you about grade 11. Okay. So in grade 11 we have um we heard we learned about the structure which is called the nephron.

[01:23:27]Okay. And then what we saw from the nephron is that we have a glomeulus.

[01:23:31]Okay. So we have blood that's going to be coming out here coming in here. And then this this structure is going to basically act as a filter. Okay. So the blood's going to come on here and then it's going to filter out whatever is not needed. It's going to keep what it needs and that's going to go back into our blood system. Okay? But whatever we don't need, whatever waste products we have is going to now be collected into these tubules. These are renal tubules just to remind you. So we have a proximal convoluted tubule, we have a distal convoluted tubule, we have a loop of henley, and we have a collecting duct. Now when you think about homeostatic control of water levels, we're talking about how much water is in the blood versus how much water is in the renal tubules.

[01:24:15]Okay? So what's going to be forming in your urinal tubules is urine. And you know that urine has water. Okay? But it also has salt.

[01:24:26]Okay?

[01:24:28]So um your kidney has a dual function here where it's going to assist with the water level and it's going to assist with the salt level. But we have different hormones that are going to be doing this. Okay. So we're going to have a look at that in more detail. So this is when we're having a look at the regulation of water. So you have normal water in your blood. This is going to be your this is homeostasis or equilibrium. And then we've got something happening. So if the water level decreases, okay, the water level is now going to decrease. Maybe it's a very hot day, you're very thirsty or something and the water level decreases.

[01:25:05]When we talking about the water level, we are talking about the water level in the blood. Okay? So when the water level in the blood is going to be um less, the pituitary gland is now going to secrete ADH. ADH here is the hormone So once again this is the stimulus the receptor is going to pick up the control center is going to do the conversion. It's going to um um cause the hormone to be secreted. What's that hormone going to do? it is going to go and it's going to make the collecting ducts permeable and the distal convoluted tubule permeable more permeable. That means that water is going to be able to move out. So when the water is able to move, it's going to move from the renal tubule into the blood cuz remember you saw in the picture there are blood vessels surrounding the renal tubules. So water is now going to move from the renal tubule to the um to to the blood. So that means we're going to have more water in the blood and we're going to have a more concentrated urine.

[01:26:20]But when the water level increases, we've got too much water in the blood.

[01:26:24]Now we want the blood we want the water to move into the renal tubule. Okay.

[01:26:32]Um so so we want to sorry there's too much water there's too much water in the blood. So now we don't want more water to go into the blood. So now the pituitary gland is going to stop secretreting ADH or less ADH so that the walls be remain permeable um um less permeable sorry and then the water is going to be less water will be reabsorbed into the blood or less water will be lost because um now we're going to have enough water. Okay.

[01:27:03]So in this instance we've got um this shows you just a diagram about osmo regulation. You can see over there that the water is moving out and you can see that sodium is also moving. Okay. So there's places where sodium can move out and and um in the proximal and the distal tubule that is where you're going to have water and sodium moving out of the renal tubules into the blood. The collecting duct we're also going to have water going out. But in this loop of Henley part we're going to have this is the section where you have water that can go either way and your sodium can also go either way.

[01:27:40]So this is now the regulation of salt.

[01:27:42]The blood and tissue fluids are affected by the presence of solutes, dissolved substances. Sodium and potassium are salts that are found in the body fluids.

[01:27:51]Sodium is important in the body for good nerve and muscle functioning. Okay. So we need sodium. But when they are increasing above normal um things need to be done. Okay. So when the salt level decreases, this is the stimulus once again. Salt level decreases.

[01:28:09]The adrenal gland secretes more eldoststerone. The adrenal gland is this gland that is found above the kidney. So this is your kidney. This is your adrenal gland. And it secretes eldoststerone.

[01:28:20]And then the reabsorption of sodium ion increases. So now you don't have enough sodium in your body. The adrenal gland is going to secrete aldoststerone.

[01:28:28]You're going to have more reabsorption of sodium and this salt level is going to return back to normal. When you've got too much salt in the body, the adrenal gland stops secretreting eldoststerone. Reabsorption of sodium ions into the blood decreases. So it stays in the renal tubules and the salt level in the blood decreases and goes back to normal. Okay. So um that is basically how it works. So where do learners get confused? Learners confuse ADH and eldoststerone. Okay. So ADH it stands for antidiuretic hormone.

[01:29:03]Okay. So, one of our colleagues likes to say it's the antip hormone. Okay.

[01:29:08]Because it's the one that's got to do with the water levels. Okay. ADH. And then the aldoststerone that is the one that has got to do with salt. Okay. So, um the other thing I wanted to tell you great Charles before we go into the questions is that um learners get confused with these different hormones. Okay? and they get confused with the control centers and everything that is happening right um you just need to keep your what's about you need to remember what is the which which is what is the gland what does this gland secrete what is the function of that hormone okay what is that hormone do what is the where's what's the target organ what's it going to do there okay and then also remember that like I said it's going to do a lot with um investigative questions and they can bring in cellular respiration look at that question was talking about fat fat loss. Now we're talking about thyroxytocis but now they're asking us about fat loss. Now you must think about metabolism and how does this work? Um they like to bring in things like cellular respiration. Um they can bring different uh different things like I told you the salt and the water work you know sort of hand in hand. So um they like to bring in more than one concept right. So it can become very it can become difficult and tricky right. So when you are looking at an investigative question, here we have an investigative question on hyperaldderonism.

[01:30:34]Once again, not something that you're going to be taught, but this question is going to tell you about it. It's a disorder and it's caused by the over secretion of aldoststerone and has been linked to high blood pressure in humans.

[01:30:47]So it's got to do with over secretion of aldoststerone. So when you see that, you must already think adrenal gland.

[01:30:58]You must already think increase in aldoststerone because it says over secretion and it's been linked to high blood pressure. So now they're saying that they're noticing that now this high blood pressure is a problem. So scientists investigated the influence of increased aldoststerone levels on blood pressure.

[01:31:16]So they want to investigate now what is the influence of this eldoststerone on the blood pressure. So what did they do?

[01:31:24]They took 1,688 healthy volunteers aged 55 and and and they participated in the investigation. The participants blood pressure was measured and recorded before the start of the investigation.

[01:31:42]The participants were injected with a dose of eldoststerone in the morning and their blood pressure was measured every hour for 12 hours. This procedure was followed over four days in for each individual and the average blood pressure was calculated. All participants followed the same diet during the period of the investigation.

[01:32:00]Okay. So when so let's just talk about what this was about. First let's understand they want to do an investigation to see if the the increase in eldoststerone was what caused the the blood pressure. Okay. Or what effect it had on the blood pressure. That's what they wanted to discover. So what they did is they took healthy individuals of a certain age. They took a large number as you can see over there and they they first took their their normal their blood pressure and then they injected them with aldoststerone.

[01:32:29]Okay. So why must they be healthy? They need to be healthy so that you can see now when you inject aldoststerone what is it doing to the blood pressure. So we need to see in a healthy individual what is their blood pressure. Then we give them the eldoststerone to see is this increase in the eldoststerone causing anything with their blood pressure.

[01:32:46]Right? And then you do it over a period of time because you need to it has to be reliable. You can't just do it now and say okay this is my answer. The whole point of reliability grade 12s is that if I have to do if if somebody has to look at this method of of this investigation and they have to conduct this investigation anywhere else in the world they are supposed to get similar results. Okay. that what makes the the investigation reliable.

[01:33:13]All um and then all all of them followed the same diet during the period of investigation. Why is that important?

[01:33:18]Because diets can also influence our results. Okay? So these are the things you need to think about when you're looking at an investigation. And then these speech bubbles are the ones that are supposed to be going off in your head. You're supposed to be asking asking yourself what is the aim? What is the independent and dependent variable?

[01:33:36]How can we ensure reliability or how did they ensure reliability? Validity, control versus experiment, controlled variables. Okay, these are the kind of things that we need to think about. Now we look at the questions. Ah, and law lo and behold this is the questions they are asking us. Independent variable, dependent variable give two reasons why the results of the investigation may be considered reliable. Can you see when you already discuss the investigation with yourself and you ask yourself those speech bubbles I want you grade 12 when you get an investigation I want you to write down on the side what did Mrs. Mar show me. She showed me these speech bubbles. On your question paper, you write down these different speech bubbles. When you read the investigation, you already try to ask yourself, answer these kind of questions. Do I know these variables?

[01:34:21]Can I think about these variables? Which ones have they given me? Which ones do I need to think about myself? Okay. So, name the gland that secretes eldoststerone. Adrenal gland. Identify the independent variable. It is the eldoststerone level. Yes. the industrial or the increased eldoststerone level and the dependent variable will be the blood pressure. So you cannot say the effect of the blood pressure. The effect is the relationship that you are investigating.

[01:34:47]It is not a variable. The effect is not the variable. The blood pressure is the variable. The aldoststerone level is the one that's being administered. The exam the the person who's doing the experiment is go the investigator is going to be giving the the aldoststerone. Then they're going to be measuring the blood pressure to check how the blood pressure was influenced by the aldoststerone. Therefore, the blood pressure is the dependent variable.

[01:35:15]Two reasons why the results of the investigation may be considered reliable. And they are reliable because they use 1,688 volunteers, which is a large group, and the procedure was done four times for each individual. Okay?

[01:35:29]So, it's not like they just took it one time during the day. They did it four times. They tested that one four times to see that is my result liable.

[01:35:38]Explain two reasons why it was important for the participants to follow the same diet during the investigation. Why was it important to follow the same diet?

[01:35:46]Because all our factors should be kept constant so that we only have one independent variable to ensure the validity. So the one independent variable is going to be the aldoststerone levels. So the all the other factors your diet and everything must be kept constant because that can affect Diet in this instance can affect your blood pressure but it can also affect your results of your aldoststerone. So we need to keep everything constant so that only the aldoststerone's effect can be checked on the blood pressure. Are you with me?

[01:36:18]Explain why the participants blood pressure was measured before the start of the investigation. Right? Why did we measure it at the start? So that we can compare the blood pressure before and after the administration of the aldoststerone. Okay? So you cannot just say um we measured the eldoststerone. Oh yes, this is definitely a factor because the eldoststerone the blood pressure is so high. No, what was this patient's blood pressure before you started with the aldoststerone? Maybe this person had high blood pressure. We don't know. So that's why you have to take it in the beginning so that you have something to compare it to. So you can say okay if everything was kept constant and the blood pressure increased it has to be then because of the aldoststerone.

[01:36:58]Explain why the levels of salt in the urine of participants is expected to decrease after being injected with aldoststerone. H So this has got to do with what you already know. Why do you think this would be? Because high levels of eldoststerone is going to result in the increase of permeability of the renal tubules which will result in more salt being reabsorbed. Okay. So this is basically just answering to yourself that what does the increase um of eldoststerone do.

[01:37:30]Now we've got a next question on um thyroxine. Okay. So let's look at the the the the flow diagram first. Here we are showing gland Y. They're showing us the pituitary gland. They're talking about SA TSH and thyroxine.

[01:37:45]Okay.

[01:37:47]So now they are not telling us what's happening to the level of dioxin but they tell us here there's more TSH and there's less TSH. So let's start here with the pituitary gland. The pituitary gland is secretreting more TSH. So if it secretes more TSH, it's going to stimulate this gland to secrete thyroxine. So this gland has to be the thyroid gland.

[01:38:15]And then it's going to stimulate it to secrete more thyroxine.

[01:38:21]Right? So I think this is going to be more thyroxine because we know that's what it does. Okay? And when the thyroxine levels are too high, the buty gland is going to be secrete stimulated to secrete less TSH so that less thyroxine can be secreted to bring back the level.

[01:38:37]Name the type of interaction it is negative feedback. What is gland Y? We discussed it. It's the thyroid gland.

[01:38:47]The disorder that is characterized by the enlargement of gland Y. So when gland Y is enlarged, what is it called?

[01:38:53]It's goer. Remember Agnes also did it with you. And what is one function of thyroxine? Um it's got three functions also. It regulates the metabolic rate, affects the growth and functioning of the heart and the nervous system and influences bone development and muscle control.

[01:39:12]Describe the role of the pituitary gland in correcting the level of thyroxine at X. Okay. So at X the level of thyroxine is going to be um okay. So it's going to correct that. So that one we said that that is when the level of thyroxine is low. How are they going to correct it?

[01:39:31]The buti gland is stimulated for more TSH to be secreted. It stimulates gland Y to secrete more thyroxine. Explain why a continuous under secretion of thyroxine may lead to an increase in body mass. So this is now saying that over time we have lot a decrease in thyroxine. So remember thyroxine is in charge of your metabolic rate. So if your metabol metabolism slows down so you are going to have a decrease in the usage of your nutrients because your metabolic rate is not going to be breaking them down. So there are going to be excess nutrients or fat which will be stored in your body. Okay. So basically you must understand that uh um um thyro high thyroxine high metabolic rate it's going to stim over a long period of time will stimulate weight loss. Okay because it's going to be using up the nutrients quickly and when it's low thyroxine over a long period of time we're going to have a increase in weight because more nutrients are going not going to be used and more nutrients are going to remain stored in the body.

[01:40:37]Okay, let me move on to our last question. The blood glucose levels in a healthy person when not eating is between 3.9 and 7.1.

[01:40:47]The table below shows the blood glucose levels in a healthy person who ate one meal. Also very important when we are talking about glucose or we're talking about anything, it's important that we always mention the blood, carbon dioxide levels of the blood, glucose levels of the blood, um salt levels of the blood, water levels of the blood. Okay, it's important that we state where are we talking about this because they could be different places in our bodies.

[01:41:10]So this is a blood sugar of a healthy person who ate only one meal. Okay, so this is in a period from 7:00 in the morning to 5:00 in the afternoon and they're saying that the person only ate one meal. Name two hormones involved in the normal homeostatic control of blood glucose blood glucose level. It's insulin and glucagon. Yes. or name the organ in the body that secretes the hormones name. So which ones they do? It is the pancreas.

[01:41:40]It's the eyelets of lunger hands in the pancreas which secrete insulin and glucagon.

[01:41:47]Between which hours of the day did the person eat? H what would give us that indication? Now the second one is use the evidence in your table to give one reason for your answer. So what do you think is going to happen? So let's just look at the trend here. 7:00 in the morning it was 4.2. 8:00 it was 4.2.

[01:42:06]9:00 it went to 8.4. Then at 10:00 it was 7.6. 11:00 7.1 12:00 5.1 1:00 4.8 2:00 3.1 3:00 4.1 4:00 4.3 5:00 4.6. So from what I can see over here is that we have it we had a stable then we had a large increase at this point then it started decreasing until we got to about this point where it started increasing again. Okay. So we would say it would be at 9:00 in the morning between 8 and 9.

[01:42:42]That is when the person ate cuz it asks us between which hours. If it it has to say between which hours remember it must have time to increase. So it has to be between 8 and 9. And what is your evidence? The evidence is that the blood glucose level increas the blood blood glucose level increases at that point.

[01:43:00]Okay.

[01:43:04]Explain the change in the blood glucose level between two and three. So between two and three what happened? It increased. So why do you think this happened?

[01:43:12]Because the blood level it decreased to below 3.9 at two and this stimulate the island the the the pancreas now to secrete glucagon. So what happens what they're saying is that our blood sugar was stable but then they she had a meal.

[01:43:27]So then insulin came to work and when insulin worked it converted the glucose into glycogen and that's why the blood glucose decreased. But now between 10 between 8:00 then 2:00 there was no food. So at 2:00 the the the the body realized that 3.1 is very very low. How do we know this? Let's just go quickly back to the beginning. What did they tell us? They tell us something that was very important. They told us here is that when a person is not eating the blood glucose is between 3.9 and 7.1.

[01:43:56]So now we have reached a point where we are now at 3.1. So that is low. So that is now stimulating the pancreas to secrete glucagon.

[01:44:09]So the blood glucose levels it decreased to below 3.9. At two, this stimulated the pancreas to secrete glucagon, which stimulates the conversion of glycogen to glucose, therefore increasing the blood glucose levels at three. So it stimulates the conversion of glycogen into glue to glucose. Stimulates the liver to increase the to to stimulate the conversion of glycogen to glucose and then it increases the blood glucose levels. Describe how blood glucose levels would have been different after 10 if the person suffered from diabetes.

[01:44:43]Melatus H. So after 10 what would happen in a person with diabetes? Their levels would remain high for a longer period because remember especially if it's not um a diabetes that is not treated. Okay.

[01:44:56]If they are not on medication then this blood sugar this this this um high levels of blood sugar will remain higher for a longer period of time.

[01:45:08]Okay. So grade 12s um that brings us to the end of today's lesson. What I think our takehome from this is that this topic really can be very complicated.

[01:45:19]But as you can see there were also some easy marks here and there. They asked you for um the gland to name the gland.

[01:45:25]They can give you the pictures of the glands. There are definitely some easier questions to be had to be um gotten as well. But you need to work hard. Um go through all your scientific investigation questions. Make sure that you practice them all the time. You you will see it in the June exam. You definitely will have a scientific investigation. So, make sure that you are prepared for that. And then next week, please join us for thermmorreulation.

[01:45:51]Um I think yeah, we're going to have a lesson on thermmorreulation next week.

[01:45:55]And then your final lesson before your exam is going to be a revision lesson.

[01:45:59]So, please make sure to stay tuned um and and join in so that you can be fully prepared for your examinations. Good luck.