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Boardworks GCSE Additional Science: Biology Homeostasis

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Presentation on theme: "Boardworks GCSE Additional Science: Biology Homeostasis"— Presentation transcript:

1 Boardworks GCSE Additional Science: Biology Homeostasis

2 Boardworks GCSE Additional Science: Biology Homeostasis

3 Boardworks GCSE Additional Science: Biology Homeostasis
A day at the sauna Boardworks GCSE Additional Science: Biology Homeostasis How does the body react to change? Teacher notes This illustration contains several discussion points relating to homeostasis, including: Steamy sauna This section of the illustration shows some of the typical physical responses of the body to a high environmental temperature, including vasodilation (redness) and sweating. Snow This section of the illustration shows some of the typical physical responses of the body to a low environmental temperature. These include vasoconstriction and shivering. Water cooler This section of the illustration shows someone getting a drink from a water cooler. Thirst is increased when the body is exposed to high environmental temperatures, due (in part) to increased sweating. Snacks This section of the illustration shows someone being reprimanded for snacking on crisps and chocolate. Eating sugary foods causes blood sugar levels to rise, which causes the pancreas to produce insulin.

4 Boardworks GCSE Additional Science: Biology Homeostasis
Saving energy? Boardworks GCSE Additional Science: Biology Homeostasis 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.

5 Boardworks GCSE Additional Science: Biology Homeostasis
What is homeostasis? Boardworks GCSE Additional Science: Biology Homeostasis The body uses so much energy, even during sleep, because it must maintain a constant internal environment. This process of keeping things the same is called homeostasis. A series of automatic control systems ensures that the body maintains a constant temperature, and steady levels of water, ions and blood sugar. Homeostasis allows the body’s cells to work at their optimum.

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Keeping comfortable Boardworks GCSE Additional Science: Biology Homeostasis Teacher notes This three-stage animation can be used to introduce the concept of homeostasis in terms of responding to change in external conditions.

7 The organs of homeostasis
Boardworks GCSE Additional Science: Biology Homeostasis Teacher notes This activity could be used as a starter exercise to work on homeostasis.

8 Boardworks GCSE Additional Science: Biology Homeostasis

9 Why control temperature?
Boardworks GCSE Additional Science: Biology Homeostasis Environmental temperature is constantly changing. One minute it can be very hot, the next very cold. Despite this, the body must be kept at a constant temperature of 37 °C. Why? This is the optimum temperature for the body’s enzymes. Teacher notes See the ‘Enzymes’ presentation for more information on enzymes and denaturing. Even slight changes in body temperature can have a life-threatening effect on health. If body temperature falls too low, reactions become too slow for cells to survive: too high, and the body’s enzymes are at risk of denaturing.

10 What is core body temperature?
Boardworks GCSE Additional Science: Biology Homeostasis The vital organs located deep within the body, such as the heart, liver and kidneys, are maintained at 37 °C. This is the core body temperature. Skin temperature at the body's extremities, such as the fingers and toes, is usually lower than the core body temperature. Photo credit: © 2007 Jupiterimages Corporation Teacher notes Clinical temperature readings are usually taken using a thermometer, digital probe or heat sensitive strip. Temperatures in the ear, mouth and rectum most closely mirror core body temperature. On a warm day, skin temperature may be just 1 °C lower than the core body temperature, but on a very cold day it could be up to 9 °C lower.

11 Finding the right balance
Boardworks GCSE Additional Science: Biology Homeostasis Core temperature is maintained by balancing heat gain and heat loss. How can heat be gained? movement and exercise shivering vasoconstriction wearing extra clothing. How can heat be lost? Photo credit: © 2007 Jupiterimages Corporation sweating vasodilation removing extra clothing.

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Too hot…or too cold? Boardworks GCSE Additional Science: Biology Homeostasis Teacher notes This five-stage animation illustrates what would happen to a boy and girl in extreme environmental conditions who are unable to thermoregulate. The girl is unable to vasodilate or produce sweat to help cool her down, which speeds up the rate at which she develops heatstroke. People who have anhidrosis – an absence or severe reduction of sweating – have a dangerously high risk of heatstroke in hot weather, which can rapidly be fatal if untreated. In a person who can thermoregulate, sweating will lead to dehydration in extreme heat, which results in additional heatstroke symptoms to the ones shown in the animation.

13 Finding the right balance
Boardworks GCSE Additional Science: Biology Homeostasis Teacher notes This two-stage animation introduces the physiological and behavioural mechanisms of thermoregulation.

14 How is temperature controlled?
Boardworks GCSE Additional Science: Biology Homeostasis Body temperature is monitored and controlled by temperature receptors in the skin and brain. hypothalamus These receptors detect changes in the temperature of blood flowing through those areas. The thermoregulatory centre in the brain is called the hypothalamus. If body temperature deviates from 37 °C, the hypothalamus and skin receptors send out electrical signals that trigger actions or behaviours that increase or decrease heat loss.

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What’s in skin? Boardworks GCSE Additional Science: Biology Homeostasis Teacher notes Students could work individually or in small groups, with mini-whiteboards used to convey the answers.

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Why do we shiver? Boardworks GCSE Additional Science: Biology Homeostasis When core body temperature drops, muscles begin to twitch. This rapid and contraction and relaxation of the muscles is called shivering. Shivering generates heat, which raises body temperature. Goose bumps involuntarily appear when a person becomes cold. Goosebumps are caused by the tiny muscles at the base of body hairs pulling the hairs erect. Photo credit: © 2007 Jupiterimages Corporation The upright hairs trap an insulating layer of air, which helps reduce heat loss.

17 Vasoconstriction and warming up
Boardworks GCSE Additional Science: Biology Homeostasis Why do people go pale when they are cold? When core body temperature falls, blood vessels in the skin get narrower. This is called vasoconstriction. Vasoconstriction 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.

18 Vasodilation and cooling down
Boardworks GCSE Additional Science: Biology Homeostasis Why do people turn red when they are hot? When core body temperature rises, blood vessels in the skin get wider. This is called vasodilation. Vasodilation allows a larger volume of blood to flow near the skin surface, transferring heat to the environment. This cools the body down. Additional cooling occurs with the production of sweat from sweat glands. As the sweat evaporates it transfers heat away from the body.

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Responding to change Boardworks GCSE Additional Science: Biology Homeostasis Teacher notes This activity could be used to check students’ understanding of how the skin responds to temperature changes.

20 Temperature control in newborns
Boardworks GCSE Additional Science: Biology Homeostasis Sayid has a baby sister. Samira was born premature and is too young to control her temperature. An incubator helps to control her temperature, using negative feedback. Teacher notes At 32ºC infants are able to main body temperature using minimum amounts of oxygen and energy. A temperature range of between 32°C and 35°C is called a neutral thermal environment. The air around Samira is kept at 32 °C. Why is it not keep at 37 °C?

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How do incubators work? Boardworks GCSE Additional Science: Biology Homeostasis Teacher notes This five-stage animation can be used to introduce the general principle of negative feedback. Students could be asked to draw an equivalent diagram of how the body uses negative feedback to control body temperature, before being shown the animation on the next slide.

22 Negative feedback in the body
Boardworks GCSE Additional Science: Biology Homeostasis Teacher notes This five-stage animation can be used to illustrate how the body uses the principle of negative feedback to control body temperature. Students could be asked if they know of other examples of negative feedback in homeostasis.

23 Thermoregulation: true or false?
Boardworks GCSE Additional Science: Biology Homeostasis Teacher notes This true-or-false activity could be used as a plenary or revision exercise on thermoregulation, or at the start of the lesson to gauge students’ existing knowledge of the subject matter. Coloured traffic light cards (red = false, yellow = don’t know, green = true) could be used to make this a whole-class exercise.

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25 Boardworks GCSE Additional Science: Biology Homeostasis
Why is water important? Boardworks GCSE Additional Science: Biology Homeostasis The human body is about 60-70% water. Water molecules and ions constantly move in and out of cells, and are essential for all life processes. Dehydration (loss of too much water from the body) damages cells. How is water gained and lost? Teacher notes See the ‘Movement In and Out of Cells’ presentation for more information on cells and osmosis. Water is produced by the body during respiration, and absorbed from food and drink. Water is lost from the body in exhaled air, sweat, urine and faeces.

26 Dehydration and its causes
Boardworks GCSE Additional Science: Biology Homeostasis 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 Photo credit: © 2007 Jupiterimages Corporation Teacher notes The kidneys filter waste products from the blood, and control water balance in the body. Caffeine and alcohol are diuretics – drugs that increase urine production. The drug ecstasy is an anti-diuretic and reduces the volume of urine produced. People taking ecstasy are at risk of overheating and dehydration. However, drug users drinking an excess of water to counteract this effect are at risk of water intoxication, which can result in digestive problems, brain damage and seizures. More information about dehydration is available at breathing dry air caffeine and alcohol diarrhoea.

27 Controlling water levels
Boardworks GCSE Additional Science: Biology Homeostasis Teacher notes This activity could be used to as an introduction to osmoregulation and how the hypothalamus and kidneys control water levels. Students could also be asked how negative feedback is involved in this control system.

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How do the kidneys work? Boardworks GCSE Additional Science: Biology Homeostasis Teacher notes This completing sentences activity could be used as a plenary or revision exercise on osmoregulation. Students could be asked to write down the missing words in their books and the activity could be concluded by the completion on the IWB.

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30 Boardworks GCSE Additional Science: Biology Homeostasis
What is blood glucose? Boardworks GCSE Additional Science: Biology Homeostasis Glucose is a type of sugar used by the body to provide energy. Sometimes there is too much glucose in the blood, and sometimes there is not enough. What affects the level of blood glucose? Eating causes blood glucose levels to rise. Vigorous exercise causes blood glucose levels to fall. Photo credit: © 2007 Jupiterimages Corporation How does the body regulate blood glucose levels?

31 Controlling blood glucose
Boardworks GCSE Additional Science: Biology Homeostasis Between meals, blood glucose levels are topped up from stored deposits in the liver and muscles. After a meal, blood glucose rises but quickly returns to normal. Where does the excess go? Why not leave it in the blood? Excess glucose makes the blood plasma and tissue fluid around cells too concentrated. This can severely damage cells, for example, causing crenation in red blood cells. Teacher notes See the ‘Movement In and Out of Cells’ for more information about how osmosis affects animal cells. However, low blood sugar levels can be equally as dangerous, as it can make cells swell up and burst. This is called lysis.

32 The pancreas and blood glucose
Boardworks GCSE Additional Science: Biology Homeostasis pancreas Blood glucose levels are monitored and controlled by the pancreas. The pancreas produces and releases different hormones depending on the blood glucose level. Insulin is released when blood glucose levels are high – the liver stores excess glucose as glycogen. Teacher notes See the GCSE Science (Biology) ‘Hormones’ presentation for more information on blood glucose, insulin and diabetes. Glucagon is released when blood glucose levels are low – the liver converts stored glycogen into glucose and releases it into the blood.

33 Maintaining safe glucose levels
Boardworks GCSE Additional Science: Biology Homeostasis Teacher notes This activity can be used to summarize the effects of eating and exercise on blood glucose levels, and how insulin and glycogen return blood glucose levels to normal.

34 Maintaining safe glucose levels
Boardworks GCSE Additional Science: Biology Homeostasis Teacher notes This five-stage animation can be used to illustrate how the body uses the principle of negative feedback to control blood glucose levels. Students could be asked to draw a modified diagram for the abnormal control of blood glucose levels in a person with diabetes.

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36 Boardworks GCSE Additional Science: Biology Homeostasis
Glossary (1/3) Boardworks GCSE Additional Science: Biology Homeostasis ADH – The hormone released from the pituitary gland that acts on kidneys and blood vessels to maintain the body’s water balance. dehydration – The loss of too much water from the body. homeostasis – The constant regulation of the body's internal environment. hyperthermia – Dangerously high body temperature. hypothalamus – The part of the brain that helps to regulate the body's internal environment. hypothermia – Dangerously low body temperature. glucose – The main source of energy for the body.

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Glossary (2/3) Boardworks GCSE Additional Science: Biology Homeostasis glucoregulation – The homeostatic control of the body’s blood sugar level. glycogen – A storage form of glucose, found in the liver and muscles. insulin – A hormone involved in the control of blood sugar, and which is reduced or absent in people with diabetes. kidney – The bean-shaped organ that filters the blood and produces urine. negative feedback – A stabilizing mechanism that slows down or reverses a stimulus.

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Glossary (3/3) Boardworks GCSE Additional Science: Biology Homeostasis osmoregulation – The homeostatic control of the body’s water and ion balance. pancreas – The organ that secretes the hormone insulin. thermoregulation – The homeostatic control of the body’s temperature. vasoconstriction – The narrowing of the blood vessels in the skin in order to reduce heat loss. vasodilation – The widening of the blood vessels in the skin in order to increase heat loss.

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Anagrams Boardworks GCSE Additional Science: Biology Homeostasis

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Multiple-choice quiz Boardworks GCSE Additional Science: Biology Homeostasis Teacher notes This multiple-choice quiz could be used as a plenary activity to assess students’ understanding of homeostasis. The questions can be skipped through without answering by clicking “next”. Students could be asked to complete the questions in their books and the activity could be concluded by the completion on the IWB.


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