1. B4 Homeostasis Route map Over the next 12 lessons you will study : Friday 21 October 2011 B4.1 Keeping the body constant B4.2 Negative feedback mechanisms B4.3 How do enzymes work B4.4 Factors affecting enzyme function End of module test B4.5 Getting hot, getting cold B4.6 Controlling your core temperature B4.7 Responses to changes in core temp B4.8 Osmosis and diffusion B4.9 Active transport in cells B4.10 Water homeostasis B4.11 Water homeostasis by ADH B4.12 When homeostasis goes wrong

3. Decide whether the following statements are true or false: Introduction: The control of the body’s internal environment is extremely important for us in terms of survival. Survival depends on our ability to adapt to changing environmental conditions. Although there are many more the two crucial ones you are going to study in this topic are temperature control and water balance. Your body is full of inputs and outputs and homeostasis is happening all the time. This process is controlled by your brain, receptors which detect change and effectors which make your body change it’s internal environment. Extension questions: 1: What is the normal temperature of the human body and what does the body do a) when it becomes too hot and b) too cold ? 2: Explain how the human body a) generates heat and b) loses heat to the surroundings ? 3: Explain two ways in which humans have adapted to survive extreme cold and extreme heat ? 4: Why do human need to maintain correct hydration and how do humans a) gain water and b) lose water from cells ? Know this: a: Know that keeping conditions the same inside the human body is called homeostasis b: Know that body temperature, blood sugar and pressure and water levels are all controlled within narrow limits. Friday 21 October 2011 B4.1 Keeping the body constant

4. B4.1 a Look at the photograph and information and answer all the questions: What key organs are involved in maintaining the correct levels of dissolved oxygen (O 2 ) in the blood ? Explain how the body gains and lose water and what key organs control correct hydrations levels in the body ? Homeostasis is the maintenance of a constant internal environment within the body, for example water balance , blood sugar and body temperature Each of these internal ‘Controls’ is maintained by a separate ‘Mechanism’. The kidneys are very important . They are responsible for regulating blood water levels, re-absorption of substances into the blood, maintenance of salt and ion levels in the blood, regulation of blood pH, and excretion of urea. Homeostasis in humans body temp blood sugar body hydration blood pH blood nutrients blood pressure blood urea blood oxygen Key concepts

5. B4.1 b Look at the photograph and information and answer all the questions: Negative Feedback tends to restore systems to their original level. Homeostasis is achieved by a negative feedback and involves Change in level of an internal factor (change from norm level) Detected by receptors / impulse send to hypothalamus Activates effectors / stimulates corrective mechanism Level of factor returns to norm Explain why humans have to maintain a core body temperature of 37 o C ? Other than sweating what other responses can the body make to help lose heat from its core ? Other than shivering how else doe the body generate or slow heat lost from its core ? set point internal temp 37 o C Stimulus: rising temperature Stimulus: falling temperature Response: sweating Response: shivering Feedback control Key concepts

6. B4.1 Plenary Lesson summary: receptor response centre constant Friday 21 October 2011 If a baby is born very prematurely it cannot carry out homeostasis and may need to be placed in an incubator in the hospital. The incubator was developed in the 1950s and has saved countless lives. It works by keeping the environment around the baby very constant whilst making sure the baby receives the right amount of food and water. How Science Works: Research into feedback in control systems and how negative feedback helps the body control internal conditions like body temperature, blood sugar and pH. Preparing for the next lesson: The body needs to keep it’s internal environment ________. Changes in temperature, blood sugar or pH for example are detected by _________ cells. This information is then passed to the processing __________ where a _________ is coordinated to return the internal environment back to normal levels. Decide whether the following statements are true or false : False True 3: Babies cannot control their own internal body temperature as well as adults ? False True 2: The body can survive great variations in temperature and still survive ? False True 1: Both blood pH and blood sugar are controlled tightly by the body ?

8. Friday 21 October 2011 Extension questions: 1: Write down two objects or systems in your house that use negative feedback ? 2: Write a definition of negative feedback ? 3: Explain why conditions in the body never stay quite the same ? 4: How does the human body reverse a) the effects of heat loss and b) the effects of heat gain ? 5: In a car how does the driver maintain a constant speed ? Know this: a: Know that internal conditions in the body are controlled by negative feedback. b: Know that the body responds to change in order to reverse the effects of that change. Introduction: Negative feedback systems are all around you. For example if the temperature in your fridge goes up the motor turns on to cool it down. Your body also uses negative feedback to control it’s internal environment. Example: An incubator. If the temperature in an incubator falls too low the heater is switched back on and the temperature goes back up. When the temperature is high enough the heater is switched off. This type of control is called negative feedback. B4.2 Feedback in control systems

9. B4.2 a Look at the photograph and information and answer all the questions: Look at the diagram opposite left, what happens when blow sugar levels become low ? Why is it important for the body to control blood sugar levels ? Feedback control is the basic mechanism by which systems, whether mechanical, electrical, or biological, maintain their equilibrium or homeostasis. In the higher life forms, the conditions under which life can continue are quite narrow. An everyday example of a feedback control system is an automobile speed control, which uses the difference between the actual and the desired speed to vary the fuel flow rate. Since the system output is used to regulate its input, such a device is said to be a closed-loop control system set point 90 mg/ml blood sugar Stimulus: low blood sugar Receptor: Detects low blood sugar Process centre: Receives and processes information Response: Norm blood sugar levels Effect: Bring about change glucagon released Stimulus: high blood sugar Receptor: Detects high blood sugar Process centre: Receives and processes information Response: Norm blood sugar levels Effect: Bring about change insulin released Key concepts

10. Diabetics cannot control their own blood sugar, which hormone can they no longer produce ? During your sleep which hormone acts on the liver and muscle tissue to keep blood sugar levels constant ? The blood sugar level is the amount of glucose in the blood. Normally blood glucose levels stay within narrow limits during the day, controlled by two hormones: Insulin and glucagon. After a sugar rich meal, insulin acts to take sugar form blood into liver and muscle tissues. Between meals glucagon does the opposite, therefore between the two hormones blood sugar levels are controlled. B4.2 b Look at the photograph and information and answer all the questions: High blood glucose is detect by the pancreas Pancreas releases insulin making liver cells to take up glucose Other body cells like skeletal muscle also take up glucose As the glucose is taken up, blood glucose levels all Key concepts

11. B4.2 Plenary Lesson summary: state effectors control artificial Friday 21 October 2011 The use of negative feedback in machines is another example of technology copying the amazing way in which the human body works. Without these control systems the body’s internal conditions would fluctuate widely meaning that we would not function properly. How Science Works: Research into how enzymes work and what role they play in digestion and cellular respiration. Preparing for the next lesson: Negative feedback allows for __________ in both natural and artificial systems. Feedback is controlled by antagonistic _________ which allow for two way control. It is the work of these effectors which allow conditions to remain in a steady _______. An incubator is an example of an ____________ feedback mechanism. Decide whether the following statements are true or false : False True 3: An effectors brings about change back to normal set levels ? False True 2: During change the body will respond to try ad reverse this change ? False True 1: Blood sugar levels are controlled by two hormones insulin and glucagon ?

13. B4.3 Enzymes Extension questions: 1: Explain how enzymes might be useful in washing powder ? 2: Digestion of food relies on both physical and chemical digestion. Which involves enzymes breaking food molecules into small molecules before their absorption ? 3: An enzyme works like a key fitting into a lock. Explain this sentence ? 4: Cyanide is a poison that stops an key cellular enzyme from working. What does cyanide do to a person ? Know this: a: Know that enzymes are catalyst that speed up many biological reactions. b. Know that enzymes will only work with certain reactions. This means they are substrate-specific. Friday 21 October 2011 Introduction: Enzymes are protein molecules in your body which are perfect at speeding up reactions in your body. Because they are so good at this we call them catalysts. Enzymes are all different in size and shape but they are all similar in that they are made up of amino acids and help to control the speed of reactions. The shape of an enzyme is very important in deciding what reaction it will help to speed up. Some enzymes work by breaking down large molecules into small molecules whilst others work by adding two molecules together. This always takes place in a special part of the enzyme called an active site.

14. B4.3 a Look at the photograph and information and answer all the questions: Explain how starch is broken down into glucose inside the digestive system by enzymes ? Which enzymes breakdown a) proteins and b) lipids ? Enzymes are the biological substance (proteins) that act as catalysts and help complex reactions occur at a sufficiently quick rate to support complex life. Enzymes complete very specific jobs only able to bind specific substrates. They are very specific locks and the compounds they work with are the special keys. Enzymes can be denatured by high temperatures. digestion cellular carbohydrases respiration lipases protein building proteases metabolism Function of enzymes in the human body Key concepts

15. Look at the above diagram explain what happens to the substrate molecules when it is bound onto the active site of the enzyme ? Explain what we mean when we say the enzyme is ‘recycled’ and used gain in further chemical reactions ? Enzymes work by binding onto specific substrate. The enzyme then speeds up the rate at which the product molecule is formed at the active site (the substrate molecules is either broken down or combined with another molecule) The product molecules now leaves the enzyme and the enzyme is recycled and used for further reactions. B4.3 b Look at the photograph and information and answer all the questions: How enzymes recognise and change substrates Key concepts

16. B4.3 c Look at the photograph and information and answer all the questions: What happens to the body’s enzymes as your core temperature goes above 42 to 43 o C ? Explain (on the level of how enzymes work() why you reaction time and speech stars to slow when you become cold ? There are many enzymes in the human body which either breakdown or build up molecules: The optimum performance of most human enzymes is at about 37 o Celsius, or the temperature of the human body. Exposing enzymes to elevated temperatures can cause them to denature, which basically means they will no longer be functional. Exposing them to lower temperatures can slow the rate at which enzymes work meaning that cellular respiration wouldn’t happen quick enough to support life. Normal body temperature Fever Coma CNS shutdown 37 o C 39 o C 41 o C 43 o C 44 o C 25 o C 30 o C 33 o C Death Coma & death Muscle failure Hypothermia shivering Temperature affecting how enzymes work Key concepts

17. B4.3 Plenary Lesson summary: protein fast specific active Friday 21 October 2011 Enzymes are used in biological washing powders because they are ideal at breaking down organic stains caused by food. Poisons such as hydrogen cyanide are known to stop important enzymes working in your respiratory system causing death quickly in humans. Hydrogen cyanide can also be used effectively as a weed killer. How Science Works: Research into how pH and temperature can affect how enzymes perform. Preparing for the next lesson: Enzymes are organic molecules made of __________. Each enzyme has a certain shape and is __________ to the compound that can join with it. The _________ site is where the compound slots into the enzyme. Without enzymes reactions cannot occur at a ______ enough rate. Decide whether the following statements are true or false : False True 3: The place in an enzyme where a reaction happens is called the active site ? False True 2: Enzymes can be both temperature and pH sensitive ? False True 1: Enzymes help speed up the rate of reaction of chemical reactions ?

19. B4.4 Extension questions: 1: Why do you think enzymes found in a) the stomach work well at a low pH (2) and b) the mouth work at a high pH of around 7.5 ? 2: Explain a) why warming enzymes increase the rate of reactions and b) very high temperatures cause the reaction to stop ? 3: What happens to the rate of reaction if an active site of an enzyme is damaged by high temps of extreme pHs ? 4: The enzymes involve in making sperm work best at 34 o C and not 37 o C, does this explain why the testis are outside the body ? Know this: a: Know what effects changing temperature and ph have on enzyme function. b: Know that each enzyme found in the human body will work best at an optimal set of conditions including pH and temperature. Friday 21 October 2011 Introduction: For reactions to take place molecules must bump into each other. At lower temperatures this happens less often so the rate of the reaction is slower. A higher temperature means more collisions and therefore a higher rate of reactions. However, if the temperature goes too high the shape of the active site changes and the enzyme is denatured. In the human body a large number of enzymes are best suited to work at 37°C because this is the normal temperature of the body. pH levels also affect how well an enzyme works. pH in the body depends on location and enzymes tend to change to suit the environment they are in. Factors affecting enzyme function

20. B4.4 a Look at the photograph and information and answer all the questions: Look at the two graphs above, explain the shape of the graph for a) temperature versus enzyme activity and b) pH versus enzyme activity ? Enzymes are denature by high temperatures. What does denatured mean ? Enzymes are used by living cells as catalysts. This means that one particular enzyme will act as a catalyst for one particular reaction but nothing else. An enzyme will work best at a particular temperature and pH, called its optimum conditions. Enzymes usually work best in warm conditions (around 40 °C) unlike chemical catalysts which often work best when they are warm. Rate of reaction Temperature o C pH Rate of reaction 0 10 20 30 40 50 60 6 6.5 7.0 7.5 8.0 8.5 Optimal conditions for enzymes Key concepts

21. B4.4 b Look at the photograph and information and answer all the questions: Explain what would happen to Cod fish if you placed in in a warm sea like the Mediterranean with an average temperature of 20 o C ? Explain why scientists are very interested at using enzyme extracted form species that live in hot spring including the bacteria pictured above ? Different species are adapted to different habitats including different environmental temperatures. In hot springs there are thermophillic bacteria that can live comfortably at 70 o C. In the Atlantic, cod live in sea temperature that rarely get above 4 o C even in the summer. Each species will have enzymes that are best suited to the environmental conditions that the organism lives. Thermophillic bacteria lives at 70 o C Atlantic cod lives at 4 o C Optimal temperature conditions for enzymes Key concepts

22. B4.4 c Look at the photograph and information and answer all the questions: Explain why mouth pH cannot be acidic and must be above 7 ? Explain why the pH of the stomach is a very acidic 2 ? In the human body there are many digestive enzymes that work at different pH. Changes in pH alter an enzyme’s shape. Different enzymes work best at different pH values. The optimum pH for an enzyme depends on where it normally works. For example, intestinal enzymes have an optimum pH of about 7.5. Enzymes in the stomach have an optimum pH of about 2. Stomach enzyme (pH 2.1) Mouth enzyme (pH 7.4) Optimal pH conditions for enzymes Key concepts

23. B4.4 Plenary Lesson summary: pH pepsin amylase optimal Friday 21 October 2011 Enzymes are worth billions of pounds to industries around the world. They are used in making medicines, food and other household goods. They are used by scientists because of the unique molecules they make or that they are able to speed up the rate of reaction making an industrial process more profitable. How Science Works: Research into what happens when the body becomes cold or hot and how we are evolved to protect our core body temperature from changes in body’s set point of 37.4 o C Preparing for the next lesson: Temperature and ____ are both very important in deciding how well an enzyme works. If temperature and pH are both right we say the conditions are __________. The enzyme which breaks down carbohydrates in your mouth is called _________ and the enzyme which breaks down proteins in your stomach is called __________. Decide whether the following statements are true or false : False True 3: Enzymes can be permanently damaged by extremes in temperatures ? False True 2: Enzymes break down large molecules into small molecules ? False True 1: Enzymes found in the stomach work at a low pH ?

25. B4.5 Getting hot, getting cold Extension questions: 1: What cellular process is heat released from in cells ? 2: Where in the body is it most important to keep at the correct temperature ? 3: How does heat produce during cellular respiration escape from the body ? 4: How is heat distributed from the core to the extremities ? 5: How does the body reduce the rate of heat loss from its core ? Know this: a: Know that the body controls its own internal core temperature to a very narrow set point of 37 o C. b: Know that humans can stay in hot environments (e.g sauna) at a temperature of over 100°C for hours without their core temperature rising significantly. Friday 21 October 2011 Introduction: Like any other object the human body will gain heat energy if it is cooler than the surrounding environment. If it is warmer then it will lose heat. Our bodies are warmed up from the inside by the energy released during respiration. This takes place constantly in our cells and allows us to keep our core body temperature at around 37°C. To keep our bodies at this temperature heat gain must be equal to heat loss. Sometimes this is easier said than done especially if the temperature around us changes. The body can also make the certain parts like the fingers and toes cooler which helps to keep other important organs at the correct temperature.

26. B4.5 a Look at the photograph and information and answer all the questions: Explain what part of your body is a) the warmest and b) the coolest. How could you show this ? Explain why your blood is important in helping your extremities keep warm and what happens to the blood supply to you fingers ad ties when during extreme hypothermia ? Cellular respiration generating heat energy C 6 H 12 O 6 (s) + 6O 2 (g) 6H 2 O (l) + 6CO 2 (g) C 6 H 12 O 6 6H 2 O 6O 2 6CO 2 We all need energy to function and we get this energy from the foods we eat. A very useful by product of cellular respiration is heat energy. Cellular respiration occurs in small parts of the cell called the mitochondria. Here glucose is broken down using oxygen forming carbon dioxide, water and heat. This heat energy is then distributed around the body by the circulatory system. Key concepts

27. B4.5 a Look at the photograph and information and answer all the questions: Explain the difference between the body’s response on a hot and cold day and how do these response help maintain a core body temperature of 37.4 o C ? Explain why your body shut off the blood supply to your fingers and toes during severe hypothermia ? Core body temperature is kept constant despite varying outside temperatures. Heat generated by both cellular respiration and muscle activity warms the core. The circulatory stream distributes this heat energy to the extremities. When you are cold or during hypothermia, the blood supply to your extremities is reduced. This can often results in frostbite during severed hypothermia. Human body responding to changing temperature Decrease metabolism increase metabolism sweating vasodilatation no sweating vasoconstriction hair lays flat undress hair stand up dress Key concepts

28. B4.5 a Look at the photograph and information and answer all the questions: In the sauna, suggest three ways in which the dog would have responded to the high external temperature ? Why did Charles Blagden place a piece of raw steak into the sauna alongside the dog ? 200 years ago, a scientist called Charles Blagden placed a living dog and raw steak in a sauna, at a sweltering 120 o C. After 1 hour, the dog was panting hard, but well. He looked back in the room to find that the steak was completely cooked. What prevented the flesh of the living mammals from cooking ? The experiment showed that homeothermic animals, such as mammals, adjust to changing external temperature changes with some sort of built-in system. Changing core temperature during a sauna Start > 1 hour > 10 hours Key concepts

29. B4.5 Plenary Lesson summary: blood cells feedback respiration Friday 21 October 2011 Humans can withstand extremes of environments living in areas that can range form very cold -50 o C to a very warm + 50 o C. This is all because we can use several physiological and behavioural strategies to helping us maintaining our core internal temperature. How Science Works: Research into how humans sense their internal core temperature and the physiological and behavioural responses humans make to maintain a steady internal core body temperature Preparing for the next lesson: The body produces it’s own heat energy in _______ during the process of _____________. Humans can tolerate extremes of heat and cold due to the way in which the body controls internal temperature. This is an example of negative ___________. Heat is transferred around the body via the __________. Decide whether the following statements are true or false : False True 3: Most heat is generated in the heart and brain False True 2: Heat energy in the body comes from the food that we have eaten. False True 1: When it is cold, heat from the extremities is redirected to the trunk.

31. Extension questions: 1: On what kind of day is washing hanging on a line most likely to dry and explain why ? 2: What causes goose pimples on your skin ? 3: What time of day do you think your core temperature would be at it’s a) highest and b) lowest ? 4: Why do you think it is so important for the brain to detect change ? 5: Why does a humid day feel unpleasant ? Know this: a: Know how the body has evolved physiological responses to cool and warm itself. b: Know how our core temperature fluctuates during the day. Friday 21 October 2011 Introduction: The brain is extremely sensitive to temperature change and it receives messages from receptor cells in the body which tell it when the temperature has changed. The brain then coordinates a response from effectors around the body which bring about either an increase or decrease in temperature until normal conditions are re-established. These effectors include muscles and sweat glands. The temperature control centre can be found in the hypothalamus in the brain. Throughout the day your body’s temperature changes depending on things like sleep, activity level and eating. B4.6 Controlling your core temperature

33. B4.6 b Look at the photograph and information and answer all the questions: Other than vasodilatation and our hair trapping a layer of air, how else does the body respond to a low core body temperature ? Give a behavioural response to a low core body temperature ? All warm blooded animals need to control their core body temperature so they can avoid hyper or hypothermia. The skin’s main role is either to increase or reduce heat loss to our surroundings. It has a number of strategies to carry out this important function. Our core body temperature needs to be maintained at 37.4 o C, so that all our enzymes can function properly. Negative feedback loop Hair stands on end insulated core Hair stands on end insulated core Physiological responses to cold environments Key concepts

34. Why are the young and old at particular risk of hypo or hyperthermia ? Even small increases in the core temperature can lead to coma and death. During hyperthermia, where core body temperature rises by only 2 to 3 o C, digestive enzymes and those enzymes that carry out cellular respiration can begin to denature and cease to function. If the core temperature is not reduced by sweating or increased blood flow to the skin it can be fatal. Negative feedback loop B4.6 c Look at the photograph and information and answer all the questions: Other than vasoconstriction and our hair laying flat, how else does the body respond to a high core body temperature ? Hair lays flat helping heat loss Vasodilatation helps heat loss through skin Physiological responses to warm environments Key concepts

35. B4.6 Plenary Lesson summary: Co-ordinated brain sweating responses Friday 21 October 2011 In addition to helping your body maintain its core temperature and preventing water loss, the skin also has several other important roles. It lets you sense the external environment allowing you to feel pain, touch and pressure. It also protects you against UV light from our sun. Skin cells are constantly replaced so any cells that are damaged by UV radiation or chemicals in the air are lost. How Science Works: Research into how the skin through vasoconstriction and vasodilatation helps the body keep its core temperature stable. Preparing for the next lesson: The hypothalamus in the _______ controls the temperature of the body. It can control a variety of __________ to bring about changes in the internal temperature. Shivering, __________ and goose bumps are all examples of __________ physical responses to a change in temperature. Decide whether the following statements are true or false : False True 3: Skin has a fat layer to help reduce heat loss form the core to the surroundings ? False True 2: Sweating works to cool down our skin by water evaporating from its surface ? False True 1: Shivering is sued by the body to help it cool the core ?