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Chapter 9


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Le Boutillier, Janelle

PSYB64Chapter 9 Temperature Regulation Thirst and Hunger HomeostasisHomeostasis is the ability to adjust physiological processes to maintain a steady internal balance or equilibriumTo achieve homeostasis regulatory systems actively defend certain set points for variables such as temperature fluid levels and weightDeviations from the bodys ideal values are rapidly assessed by the nervous system which makes appropriate internal adjustments and motivates behavior designed to regain the ideal state o Motivation activates and directs behavior The nervous system activates behavior by generating tension and discomfort in the form of drive states such as thirst or hunger and those drive states disappear when the needs are metRegulation of Body TemperatureTemperature regulations includes set point mechanisms for detecting a deviation from set point and internal behavioral elements designed to regain set pointNo matter where they live animals must maintain an internal temperature that is ideal for the normal activity of their bodies cellsAdaptations to TemperatureMammals and birds are referred to as endotherms because of their ability to maintain body temperature through internal metabolic activityAmphibians reptiles and fish are referred to as ectotherms because they rely on external factors to maintain ideal body temperature Maintenance of body temperature is influenced by an animals surfacetovolume ratio o The larger the overall volume of the body the more heat is produced by the metabolic activity o Smaller animals have more surface area relative to the overall body volume than larger animals do so small animals must use much more energy to maintain a constant body temperatureIn cold climates surface area and heat loss are reduced in animals that have compact bodies and short legs tails and earsIn warm climates animals have greater surface area in the form of slim bodies and long appendagesBehavioral Responses to Heat and ColdEctotherms are more dependent on behavioral devices because they dont share the endotherms ability to use internal mechanisms for temperature regulationBody position can be adjusted in response to changes in temperatureAnimals can change weight color and composition of their fur in response to seasonal changes in temperatureHumans use dark heavy clothing to maintain and absorb heat and light colors to dissipate and reflect heatEndothermic Responses to Heat and ColdHumans hold a set point temperature of 986degrees F 37 degrees C
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