Transcript Document
Thermoregulation • Thermoregulation Leads to Homeostasis • Endotherms- Mammals, birds, some reptiles, and numerous insects. – Tolerate small changes in the internal heat of the body • managed by maintaining a high metabolic rate and having a complex respiratory and circulatory system – allows for sustained activity not possible in the ectotherm • Can tolerate larger changes in the external environment (1300 -1800 Cal/day BMR) – A disadvantage for many species is the high need for calories Thermoregulation - Strategies • Insulation is achieved through the integumentary system (skin, hair, feathers,...) – Adaptations that greatly conserve trapped heat • 3 layers to skin – epidermis- mostly dead tissue that continually flakes off and is replaced lower epithelial cells » provides a protective layer while acting to conserve water – Mesoderm (dermis) - houses oil glands, hair follicles, nerves, & vessels » Land vertebrates can increase warmth by raising feathers and hair follicles when cold trapping in heat - goose pimples – hypodermis- consists of a layer of fat that acts as an insulator » Thick layer is called blubber in marine mammals Thermoregulation - Strategies • Circulatory adaptations – vasodilation brings blood to the skin and warms the skin – vasoconstriction shunts blood away from the skin increasing core temperature – Insects, birds and larger marine mammals can use countercurrent heat exchangers • Arteries in close proximity to veins to transfer heat throughout the length of the organism • traps heat in the core reducing loss in the extremities Thermoregulation - Strategies • Cooling by evaporative heat loss – water removes heat (KE) 50 - 100x faster than air alone through evaporative heat loss • method for cooling when the ambient temperature is above body temperature – panting in many mammals and birds, perspiration in humans (sensible and insensible) – some mammals lick themselves to increase the evaporative cooling effect Thermoregulation - Strategies • Behavioral responses – migration – invertebrates(insects) seek sun and shade much like ectotherms – honey bees will huddle to keep warm • Adjusting metabolic heat production – increasing muscle use through shivering – non-shivering thermogenesis (NST) - increase in the activity of mitochondria to increase metabolism – brown fat- around shoulders and neck increase the heat production in those areas • Feedback Mechanisms – hypothalamus- area of brain controlling temperature receives messages from cold and warm receptors located in the skin • Acclimatization- the adjustment of an organism to a new set of conditions – changing coat or shedding – changing the density of the fat layer under the dermis – changing the amount of saturated and unsaturated lipids in the membrane to resist crystallization – production of heat-shock proteins (stress-induced protein) to help resist denaturing of proteins • Energy conservation through torpor (the reduction of activity and metabolism – can be daily (sleep) of seasonal (hibernation [winter]or estivation [summer]) Thermoregulation - Strategies Thermoregulation - Strategies • Ectotherms - Most invertebrates, fishes, amphibians, most reptiles, and turtles. – tolerate larger changes in internal heat – manage by seeking out places in the environment with optimal temperature • tolerate a larger range of internal temperatures • an advantage is the low need for calories (~60Cal/day SMR) – some species may use vasoconstriction and vasodilation to transfer heat – main method for thermoregulation is by behavioral responses seeking sun and shade – Adjusting metabolic heat production • Some snakes increasing muscle use through shivering to internally incubate eggs Thermoregulation - Strategies • Heat Exchange with the Environment Adaptations