Homeostasis 1 of 26 Boardworks Ltd 2011
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A day at the sauna 3 of 26 Boardworks Ltd 2011 How does the body react to change?
Saving energy? 4 of 26 Boardworks Ltd 2011 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 fluid surrounding around his cells at just the right concentration.
What is homeostasis? 5 of 26 Boardworks Ltd 2011 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. Nervous and hormonal control systems ensure that the body maintains a constant temperature. These control systems also make sure that the body has steady levels of water, ions and blood sugar. Homeostasis allows the body s cells and enzymes to work at their optimum level.
Maintaining internal conditions 6 of 26 Boardworks Ltd 2011
Control systems 7 of 26 Boardworks Ltd 2011
The organs of homeostasis 8 of 26 Boardworks Ltd 2011
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Why control temperature? 10 of 26 Boardworks Ltd 2011 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. Even slight changes in body temperature can have a lifethreatening 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.
What is core body temperature? 11 of 26 Boardworks Ltd 2011 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. This reduces the energy lost. 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.
Measuring body temperature 12 of 26 Boardworks Ltd 2011
Finding the right balance 13 of 26 Boardworks Ltd 2011
Too hot or too cold? 14 of 26 Boardworks Ltd 2011
How is temperature controlled? 15 of 26 Boardworks Ltd 2011 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.
Maintaining the core temperature 16 of 26 Boardworks Ltd 2011
Why do we shiver? 17 of 26 Boardworks Ltd 2011 When core body temperature drops, muscles begin to twitch. This rapid contraction and relaxation of the muscles is called shivering. Shivering generates heat, which raises body temperature. Goosebumps involuntarily appear when a person becomes cold. 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.
The structure of the skin 18 of 26 Boardworks Ltd 2011
Vasoconstriction and warming up 19 of 26 Boardworks Ltd 2011 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.
Vasodilation and cooling down 20 of 26 Boardworks Ltd 2011 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.
Responding to change 21 of 26 Boardworks Ltd 2011
Negative feedback in the body 22 of 26 Boardworks Ltd 2011
Thermoregulation: true or false? 23 of 26 Boardworks Ltd 2011
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Glossary 25 of 26 Boardworks Ltd 2011
Multiple-choice quiz 26 of 26 Boardworks Ltd 2011