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B4 – Homeostasis. Overview of Topic Diffusion & Active transport Osmosis Enzymes & optimum temperature Control and Feedback systems Homeostasis and temperature.

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Presentation on theme: "B4 – Homeostasis. Overview of Topic Diffusion & Active transport Osmosis Enzymes & optimum temperature Control and Feedback systems Homeostasis and temperature."— Presentation transcript:

1 B4 – Homeostasis

2 Overview of Topic Diffusion & Active transport Osmosis Enzymes & optimum temperature Control and Feedback systems Homeostasis and temperature What happens if you get too hot or too cold? Homeostasis and water balance Hormones and water balance Kidneys

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4 Objectives Explain how diffusion and active transport work

5 Why does the colour of concentrated fruit drink change when it is added to water? Why can you smell cooked food from a distance? Smells and liquids spreading out Why can you smell perfume or aftershave when someone walks past you?

6 Diffusion Diffusion is the net movement of particles from a region of high concentration to a region of low concentration (concentration gradient). Only happens in gases or a substance in solution. It occurs because the particles move around and bump into each other and begin to spread out.

7 Changing concentrations Molecules diffuse until they are evenly spaced apart and equilibrium is reached. During diffusion molecules move from an area of high concentration to an area of low concentration often through a partially permeable membrane. Diffusion is a passive process which means that no energy is needed. high concentration low concentration

8 Concentration Gradient The difference between the concentration in each area is called the concentration gradient. The bigger the concentration gradient the faster the rate of diffusion will occur. WHAT ELSE DO YOU THINK WOULD AFFECT THE RATE OF DIFFUSION?

9 Net Movement At lower concentration gradients the rate appears slower because particles from the other side may be moving too. Because particles may move from either side we must consider the net movement of particles. Net movement = particles moving in - particles moving out

10 Diffusion

11 Why is diffusion so important? Diffusion occurs in the organ systems that control your breathing, circulation, digestion and other life processes. Diffusion is an essential process that is going on inside your body right now and keeping you alive!

12 Active Transport Active transport is the opposite to diffusion. Its when particles move from a region of low concentration to a region of high concentration. It requires energy to do this as it is going against the concentration gradient. high concentration low concentration diffusion active transport

13 What is active transport? Substances can move passively in and out of cells by diffusion until the concentration on both sides of the cell membrane reaches an equilibrium. Once they have reached equilibrium they will not appear to move anymore. Substances can continue to move in and out of a cell using a process called active transport. During active transport, protein carriers in the cell membrane ‘pick up’ particles and move them against the concentration gradient. As the name suggests, active transport requires energy from the cell, which is made available by respiration.

14 Questions What is diffusion? What is active transport? What is the difference between diffusion and active transport? What is a partially permeable membrane? Why does oxygen diffuse into the blood from the lungs? Why does food diffuse into the blood from the intestines?

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20 Objectives Explain how osmosis works

21 What is osmosis? Osmosis is a special type of diffusion. Diffusion involves gas or dissolved molecules, but osmosis only involves the movement of water molecules. Osmosis occurs across a semi-permeable membrane which has tiny holes in it. These holes are small enough for water molecules to pass through but larger molecules cannot pass through. water molecule

22 What happens during osmosis? Osmosis is the movement of water molecules from a region of high water concentration (dilute sol’n) to a region of low water concentration (conc sol’n) across a semi-permeable membrane. water molecule semipermeable membrane osmosis

23 Dilute vs. concentrated During osmosis, water molecules diffuse from pure water or dilute solution to more concentrated solutions Dilute solutions have a high concentration of water molecules. Concentrated solutions have a low concentration of water molecules.. pure water dilute solution concentrated solution

24 Osmosis and animal cells Animal cells do not have a cell wall. This means they respond differently than plant cells to the gain and loss of water. In concentrated solutions, water moves out from the cell from the cytoplasm, and causes the cells to shrivel and shrink. In dilute solutions, water moves into the cell causing the cell to swell up and burst. This is called lysis.

25 Osmosis practical

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27 Objectives Describe what an enzyme is and what conditions they work best in

28 What are enzymes? Enzymes are proteins. They are biological catalysts – they speed up the chemical reactions that take place inside all cells, but without being used up in the process. There are many thousands of different types of enzyme, and each one catalyses (speeds up) a different reaction. They are specific to each reaction due to their ‘lock and key’ structure.

29 The ‘Lock and Key’ model Each enzyme binds to a specific molecule called the reactant or substrate. The part of the enzyme to which the reactant binds is called the active site. It is a very specific shape and the most important part of the enzyme. Only the substrate that matches the active site can bind to the enzyme. This is why we call it the lock and key model.

30 What happens at the active site? enzyme substrate + enzyme- substrate complex ↔ products enzyme + ↔ + ↔↔ +

31 Lock and Key Model

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33 Why do enzymes speed up reactions? Enzymes speed up reactions by lowering the activation energy (E a ) of a reaction. The activation energy is the energy needed to start a reaction. Different reactions have different activation energies. reaction (time) energy (kJ) E a with enzyme E a without enzyme

34 How else can we speed up reactions? Another way to speed up chemical reactions is to increase the temperature. If the temperature gets too high though, the enzyme will stop working. Human body Optimum Temp = 37°C

35 Factors affecting enzymes Enzymes work at an optimum temperature and pH. If the temperature and pH changes from an enzyme’s optimum level, the shape of the enzyme irreversibly changes. This affects the shape of the active site and means that the enzyme will no longer work. When this happens we call the enzyme denatured. normal denatured heat pH

36 Enzyme Questions 1.What are enzymes also known as? 2.What do enzymes do to biological reactions? 3.What do we call the special shape on an enzyme molecule? 4.What are enzymes made of? 5.What is created when an enzyme and substrate combine together? 6.What is lost when an enzyme is denatured? 7.Write down two factors that can cause denaturing.

37 Enzyme Practical Put 5cm starch solution and 1cm amylase (enzyme) in a boiling tube Repeat this for 5 boiling tubes Place each boiling tube in a different condition and leave for 15 minutes Conditions are: Ice (0°C), Room temp (20°C), 40°C, 60°C and 80°C. CAUTION – VERY HOT WATER!!

38 Enzyme Practical After 15 minutes remove the test tube from the water bath and place in a test tube rack. Then add a few drops of iodine to each solution and observe the reaction. Record the results in a table. See if you can draw any conclusions about the temperature amylase likes to work at.

39 Results Tempe rature Group 1Group 2Group 3Group 4Group 5Group 6 0 20 40 60 80

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41 Starter Activity 1.List your senses 2.Tick which ones you used coming into the room 3.How would you tell the temperature of a cup of water without a thermometer?

42 Objectives Describe how a control and feedback system work

43 How does this greenhouse maintain its temperature? If its too cold... A receptor detects the temperature, which sends a message to a processing centre (computer), which triggers a response in the effector, which in this case turns heaters on And if its too hot... A receptor detects the temperature, which sends a message to a processing centre (computer), which triggers a response in the effector, which in this case opens ventilation flaps to allow cooling.

44 The same thing happens in the human body RECEPTORS in the body detect a change inside or outside of the body CENTRAL NERVOUS SYSTEM (CNS) co-ordinates the body’s response, made up of brain and spinal cord EFFECTORS cause a response by moving part of the body or secreting a hormone RECEPTOR In your ears EFFECTOR Muscles contract so you turn to look at them (CNS) STIMULUS Friend shouts you STIMULUS is the change your body detects Example...

45 Write a control and feedback flow diagram for each of these situations You touch a hot pan on a cooker You prick your finger on something sharp Your friends shouts your name and you turn round to look at them

46 The central nervous system (CNS) is made up of the brain and spinal cord. What is the central nervous system? cerebellum cerebral hemisphere spinal cord

47 Reflexes are fast, automatic protective biological control systems that link a stimulus to a response. Reflex reactions happen without you having to think about them – they are involuntary. This is because the central nervous system (CNS) sends electrical signals to the muscles before the brain can pick up the message. Many reflexes such as sneezing and focusing your eyes occur naturally, but other reflexes can be learned, i.e. conditioned responses. What are reflexes?

48 What types of common reflexes do you know?

49 What are neurones? Neurones are specialised cells that conduct electrical impulses through the body. A nerve is a bundle of many nerve fibres enclosed within a protective sheath. Nerve fibres are the long axons of neurones together with any associated tissues. nerve fibre nerve

50 Definitions Stimulus – Changes that receptor cells detect. Receptors – Cells that detect changes inside or outside the body. Sense organs – organs that contain receptor cells. Effectors – Organs in the body that cause a response. They can be muscles or glands.

51 Interpreting signals How can you find your reaction time? 1.Extend your arm over the edge of a table and have a partner hold a ruler between your fingers at the 0 cm mark. 2.The partner drops the ruler – catch it between your fingers and thumb as quickly as possible. 3.Repeat the test 10 times, recording the results and calculate the mean (average) distance. Then convert the distance into a reaction time.

52 Converting distance to Reaction time Distance on ruler Time 5 cm0.10 sec (100 ms) 10 cm0.14 sec (140 ms) 15 cm0.17 sec (170 ms) 20 cm0.20 sec (200 ms) 25.5 cm0.23 sec (230 ms) 30.5 cm0.25 sec (250 ms) 43 cm0.30 sec (300 ms) 61 cm0.35 sec (350 ms) 79 cm0.40 sec (400 ms) 99 cm0.45 sec (450 ms)

53 Receptor detects change Stimuli Information is sent as an electrical signals called impulses Impulse travels along nerve cells called sensory neurone. The brain or spinal cord co-ordinate a response Impulses send a message along a motor neurone to part of the body called an effector organ e.g. muscle or gland Response

54 Receptor detects change Stimuli Information is sent as an electrical signals called impulses Impulse travels along nerve cells called sensory neurone. The brain or spinal cord co-ordinate a response Impulses send a message along a motor neurone to part of the body called an effector organ e.g. muscle or gland Response

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56 Saving energy? Sayid has decided to save energy by staying in bed all day. How much of his energy do you think this will save? Surprisingly the answer is only about 30%. The other 70% keeps his body temperature at 37 °C, and the solutions around his cells at just the right concentration. The body uses so much energy, even during sleep, because it must maintain a constant internal environment.

57 Objectives Explain how your body regulates temperature

58 Homeostasis The way our body keeps its internal conditions constant is called Homeostasis. We have many different feedback systems to control the conditions of our body such as; temperature, water levels, blood sugar etc. We are constantly making and losing heat, and temperature levels have to be maintained at 37°C for our body to work properly.

59 Inside our body The inside of our head and torso is known as our core as it contains our vital organs such as brain, heart, lungs. Inside the core is where our body is the warmest because this is where most of the heat from respiration is produced. This heat is transferred to our arms and legs through our blood to keep the warm too. They often feel cold because they don’t make much heat themselves and lose heat easily because they have such a large surface area.

60 Finding the right balance Core temperature is maintained by balancing heat gain and heat loss. How can heat be gained? How can heat be lost? movement and exercise shivering vasoconstriction wearing extra clothing. sweating vasodilation removing extra clothing.

61 How is temperature controlled? Body temperature is monitored and controlled by temperature receptors in the skin and brain. These receptors detect changes in the temperature of blood flowing through those areas. The part of the brain that detects changes is called the hypothalamus. The skin has temperature receptors in its nerves. If body temperature changes from 37°C, the hypothalamus and skin receptors send out electrical signals that trigger actions to change the temperature back to 37°C

62 Body Temperature Effectors (muscles and sweat glands) carry out the response Temperature detectors in the skin detect the external temperature Temperature detectors in the brain detect the blood temperature The brain processes this information and coordinates a response

63 Diagram of skin

64 Keeping Warm Your muscles cause you to shiver (rapid contraction and relaxation of the muscles) to create heat. Goosebumps are caused by the tiny muscles at the base of body hairs pulling the hairs erect. The upright hairs trap an insulating layer of air, which helps reduce heat loss.

65 Keeping Warm Blood vessels in the skin get narrower. This is called vasoconstriction. (this is why you look pale) This is caused by contraction of the muscular wall of the blood vessels. This reduces the volume of blood flowing near the skin surface, and reduces the amount of heat lost from the body. This is when the blood vessels sink into the body to keep the blood warm.

66 Keeping Cool You sweat and heat evaporates from your sweat. Hairs lie flat so air is not trapped. Blood vessels in the skin get wider this is called vasodilation. (this is why you go red) This allows a larger volume of blood to flow near the skin surface, transferring heat to the environment.

67 Maintaining Temperature

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69 Complete the Table If your too hot you can do this to cool down If your too cold you can do this to warm up

70 Diagram of skin

71 Objectives Describe what happens if your body gets too hot or too cold

72 What happens if your body is not 37°C If the temperature falls too low, reactions become too slow for cells to survive. If the temperature gets too high, the body’s enzymes are at risk of denaturing.

73 If you get too hot - Heatstroke If your temperature goes over 40°C you can get heat stroke. You will be dehydrated, dizzy, confused and sick. You will look sweaty and pale, even though your skin is hot and dry and your not sweating much because your body is trying to conserve water. It happens easily to people who are ill (sickness and diarrhoea), people who have taken ecstasy and people who are not used to the heat.

74 If you get too hot - Heatstroke To treat a person with heatstroke it is important to cool them down as quickly as you can. Put them in a bath of cold water. If you cant do that cover them in a wet sheet and keep the sheet wet. Give them water to drink. They must be seen by a doctor as soon as possible.

75 If you get too cold - Hypothermia If your temperature goes below 35°C you have hypothermia. If it drops lower than 30°C you will pass out and be at risk of death. You will be shivering, confused, drowsy, have slurred speech, lose coordination and have cold, dry, pale skin. It doesn’t just happen in snowy places it can also happen in water, in wind and rain and even indoors! Elderly people are most at risk if their houses are cold and they don’t move around a lot.

76 If you get too cold - Frostbite Your arms and legs don’t generate as much heat as the core of your body. They also lose heat easier. When its cold the blood flow is less to those areas due to the body concentrating blood flow to vital organs, as well as due to vasoconstriction. This means they are more at risk of getting too cold, and can develop frostbite.

77 If you get too cold - Hypothermia To treat a person with hypothermia it is important to warm them up as quickly as you can. This can be done by taking them to a warm place and wrapping them n blankets and warm clothes. You can also give them something warm to drink. If they are wearing wet clothes, remove them and give them warm, dry clothes.

78 Task Design an advice leaflet giving advice to people who are off on a trekking expedition in the desert. Remember deserts are really hot during the day and really cold during the night, so you will need to give advice on what to do to stay at the right temperature, and what to do if you get too hot or cold.

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81 Objectives Explain how your body regulates water balance

82 Why is water important? The human body is about 60-70% water. Water is produced by the body during respiration, and absorbed from food and drink. Water is lost from the body in exhaled air (breathing), sweat, urine and faeces. Water molecules constantly move in and out of cells, and are essential for all life processes. Dehydration is the loss of too much water from the body and it damages cells.

83 How are water levels controlled? Water levels are monitored by the receptors in the hypothalamus. Receptors inside the hypothalamus detect changes in the concentration of salt in the blood. The higher the salt level the lower the water level. That’s why salty food makes you thirsty.

84 Dehydration and its causes Just a 1% decrease in body weight due to water loss is enough to cause mild dehydration. Mild dehydration can cause dizziness, a dry mouth and concentrated urine. Severe dehydration can cause death. What causes dehydration? heavy sweating low water intake eating salty food breathing dry air caffeine and alcohol diarrhoea.

85 Controlling water levels Normal blood levels Drinking, Eating & respiration make you have more water in your blood Sweating, Excreting & breathing make you have less water in your blood To get back to normal blood levels you make lots of urine and lose water by evaporation through sweat To get back to normal blood levels you don’t make much urine and need to take in more water through food and drink

86 Questions 1.How do we gain water? 2.How do we lose water? 3.What do we do if our water levels are too high? 4.What do we do if our water levels are too low? 5.Which organ checks what our water levels are? 6.What are the symptoms of dehydration?

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88 Objectives Explain how hormones regulate water balance

89 How are water levels controlled? Water levels are monitored by the receptors in the hypothalamus. These receptors detect changes in the concentration of salt in the blood. Depending on the concentration, the hypothalamus instructs the pituitary gland to secrete more or less of the hormone ADH (anti-diuretic hormone)

90 ADH and water regulation Osmoreceptors in the hypothalamus detect the low levels of water, so the hypothalamus sends an impulse to the pituitary gland which releases ADH into the bloodstream. ADH causes more water to be reabsorbed in the kidneys by making the wall of the collecting duct more permeable to water. This means less, more concentrated urine is made. It also increases thirst levels in the body, encouraging us to drink more. So, when ADH is present more water is reabsorbed and less is excreted.

91 Not having enough water Low blood water level causes a high salt concentration Receptors in the hypothalamus detect the high salt content More ADH is secreted into the blood The kidney becomes more permeable to water so more is reabsorbed. The bladder fills with a small quantity of urine Normal blood water level is achieved.

92 Having too much water High blood water level causes a low salt concentration Receptors in the hypothalamus detect the low salt content Less ADH is secreted into the blood The kidney becomes less permeable to water so more is absorbed. The bladder fills with a large quantity of urine Normal blood water level is achieved.

93 Water regulation by ADH Too much waterToo little water Low blood water level causes a high salt concentration Receptors in the hypothalamus detect the high salt content More ADH is secreted into the blood The kidney becomes more permeable to water so more is reabsorbed. The bladder fills with a small quantity of urine Normal blood water level is achieved. High blood water level causes a low salt concentration Receptors in the hypothalamus detect the low salt content Less ADH is secreted into the blood The kidney becomes less permeable to water so more is absorbed. The bladder fills with a large quantity of urine Normal blood water level is achieved.

94 Drugs and ADH Some drugs can affect the production of ADH. Alcohol acts as a diuretic by reducing the amount of ADH secreted. This results in increased amounts of urine produced, which in turn can result in dehydration. Ecstasy is the opposite, it increases the amount of ADH secreted. This results in reduced amounts of urine produced, so the body is not releasing any water, yet users often drink lots.

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97 Objectives Describe what job the kidneys do and explain how they work

98 The Kidneys The blood contains many small molecules such as water, glucose, salt and urea. The kidneys filter the molecules that are not needed out of the blood. Once they have done that they reabsorb any molecules that are needed back into the blood. This happens in the kidney tubules.

99 Amino Acids Amino acids are used for growth and repair. They come from proteins which we eat. They cannot be stored if they are not used though, and have to be broken down. The liver breaks them down into a substance called urea which is filtered out by the kidneys.

100 Kidneys Blood inBlood out Ureter (tube that takes urine containing the waste down to bladder) Kidneys are responsible for controlling water, glucose, salt and urea content.

101 Inside the tubules

102 Kidneys Kidneys work in 3 stages: 1. ULTRAFILTRATION - Lots of water and products of digestion are squeezed out of the blood and into tubules under pressure. 3. WASTE – excess water, excess ions and any urea are now removed through the ureter 2. SELECTIVE REABSORPTION – the blood takes back the things it wants (e.g. glucose and ions) even though this means going against a concentration gradient. Blood vesselTubule

103 Questions to answer 1.Which part of the body monitors water levels and how does it do it? 2.How do we gain and lose water? 3.How do we overcome not having enough water? 4.How do we over come having too much water? 5.How do the kidneys work? 6.What effect do drugs and alcohol have on water levels?

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105 Objectives Revise topic B4

106 Revision Brainstorm Osmosis Active Transport Diffusion What do Enzymes do? What conditions do Enzymes work best in?

107 Responses Can you write responses for each of these situations? 1.You knock an object off the table and go to pick it up 2.You have an itch on your head and scratch it 3.You feel warm so you take your jumper off StimulusReceptorEffectorResponseCNS

108 Complete the revision diagram


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