chapter 7 - maintaining an internal balance 7.1 & 7.2
TRANSCRIPT
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Chapter 7 - Maintaining an Internal Balance
7.1 & 7.2
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Homeostasis
• human body systems are constantly adjusting to changes in the external environment to maintain a constant internal environment
• homeostasis is an active process, sometimes called dynamic equilibrium
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Optimal Human Body(Image from: http://www.liesyoungwomenbelieve.com/index.php?id=354)
• temperature: 37ºC• blood sugar level:
0.1%• blood pH: 7.35• etc.
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Homeostatic Control System(Image from: http://www.revisescience.co.uk/2010/schools/ilford/abhomeostasis.asp)
• monitor• coordinating center• regulator
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Feedback Systems
• negative feedback– signals coordinating centre to counteract
any detected changes in the same direction
– prevents a small change from becoming too large
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Negative Feedback(Image from: http://www.freewebs.com/sandra02n/)
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Negative Feedback(Image from: http://academic.kellogg.edu/herbrandsonc/bio201_mckinley/endocrine%20system.htm)
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Feedback Systems(Image from: http://ingrimayne.com/econ/AllocatingRationing/PriceAndFeedback.html)
• positive feedback– signals coordinating centre to amplify any
detected changes in the same direction– much less common– causes a small change to become larger
QuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.
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Positive Feedback(Image from: http://pespmc1.vub.ac.be/feedback.html)
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Positive Feedback(Image from: http://biologyfiles.fieldofscience.com/2011_01_01_archive.html)
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Thermoregulation
• the regulation of body temperature
• each species has an optimal temperature
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Thermoregulation
• ectothermstemperature is regulated by external
temperature
• endothermscan maintain constant body temperature
regardless of external changes
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Ectotherms & Endotherms(Image from: http://faculty.uca.edu/johnc/animalstructfu.htm)
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Thermoregulation(Image on next slide from: http://schoolworkhelper.net/2010/07/thermoregulation/)
• In humans, the hypothalamus (part of the brain) is the coordinating centre for thermoregulation.
Image taken from: http://zaborina.i.ph/photo/108/109
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Mammalian Diving Reflex
• when a mammal is submerged in cold water, the hypothalamus signals – the heart rate to slow down– blood to be diverted to the brain and other
vital organs to conserve heat
• useful in preventing hypothermia
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Mammalian Diving Reflex(Image from: http://www.celticseakayaking.com/articles/mammal.htm)