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Temperature, Osmotic Regulation, and the Urinary System. Homeostasis – the ability of living organisms to maintain internal conditions within an optimal range a steady-state physiological condition, extremely important for the proper functioning of cells. Homeostasis.
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Temperature, Osmotic Regulation, and the Urinary System • Homeostasis – the ability of living organisms to maintain internal conditions within an optimal range • a steady-state physiological condition, extremely important for the proper functioning of cells
Homeostasis • Thermoregulation (temperature) • Osmoregulation (solute and water balance) • Excretion (rids system of nitrogen-containing metabolic byproducts)
Thermoregulation • The rate of any chemical reaction is affected by temperature • The rate of reaction increases with increasing temperature • The rate of reaction decreases with decreasing temperature • Q10 is a quantitative examination of how reaction rates vary with temperature
Thermoregulation, Q10 • Q10 – the ratio between the rates of a reaction at two temperatures that differ by 10°C Q10 = RT+10 / RT • For example, if Q10 = 2, then for every 10°C increase in temperature, the rate of reaction doubles (increases by a factor of 2)
Thermoregulation, Q10 • For most enzymes, Q10 = 2 • Q10 can also be applied to metabolism (the set of all chemical reactions that occur in living organisms in order to maintain life) • In most organisms, the Q10 of metabolism is 2-3 • In some organisms, their Q10 is close to 1 • Little to no change in metabolic rate with temperature
Thermoregulation • The reactions in your body that make up your metabolism are constantly producing heat • Can be dissipated or used to raise internal body temperature • Metabolic rate and body temperature are inter-related • Lower body temperatures do not permit high metabolic rates
Thermoregulation • External temperatures affect metabolism as well • As external temperatures decrease, tremendous heat loss can occur • As body temperatures are reduced, it becomes more difficult to generate metabolic heat
Thermoregulation • Internal body heat = heat produced + heat transferred or Body heat = heat produced + (heat gained – heat lost)
Thermoreguation • Four mechanisms of heat transfer • Radiation: no direct contact; e.g., Sun • Conduction: direct transfer of heat from one object to another • Convection: involves movement of gas or liquid • Evaporation: energy loss, conversion of liquid gas
Endothermy vs. Ectothermy • Ectothermy • Lower energy requirements (more efficient at converting energy into biomass) • Typically limited to diurnal environments, tropical and semi-tropical environments, short bursts of activity • Endothermy • May be active at night; in tropics to the poles • Very high energy requirements
Thermoregulation • Organisms have evolved adaptations to regulate their body temperature (and reduce heat loss to their environment) • Changes in surface area, temperature difference and heat conduction • In Ectotherms • Presence of ’antifreeze’ (cold temps) • Different enzyme systems (hot temps)
Thermoregulation • In Endotherms • Increase muscular activity; shivering (cold temps) • Adjusting blood flow through skin (cold or hot) • Adjusting amount of heat loss through evaporation • Adjusting amount of insulation • Adjusting proportion of body parts in order to reduce or increase surface area
Thermoregulation http://dive.scubadiving.com/d2d_archive/read.php?f=1&t=920399&a=2& www.flickr.com/photos/80835774@N00/2096697676/ www.flickr.com/photos/hearman/9884614/
Thermoregulation • Adaptations to regulating temperatures can be both physiological and behavioral • Most invertebrates (ectodermic) use behavior to adjust their temperature • Orientation of body towards sun • Shivering www.flickr.com/photos/fxd/2760414614/
Countercurrent Heat Exchange • Vertebrate ectoderms, as well as some endodermic birds and mammals regulate their internal body temperature by way of a counter-current heat exchange system • Warm blood pumped from within the body is used to warm the cooler blood returning from the extremities • Ingenious! Blood leaving the warm interior loses its heat to returning vessels just before they enter (cooler) extremities
Countercurrent Heat Exchange in Action!!! • Marine birds do this as well!
Common dolphin dorsal fin vein artery
Thermoregulation • In general, ectotherms have low metabolic rates, which has the advantage of correspondingly low intake of food • Some endoderms can prevent overheating by perspiring (sweating) and panting • Mud baths are particularly useful in preventing overheating
Adaptations to Temperature Extremes • When temperatures fall below a critical threshold, the animal must resort to thermogenesis, the use of normal energy metabolism to produce heat • Shivering (muscular activity) • Nonshivering thermogenesis • Occurs primarily in brown fat (hibernating animals, babies, arctic mammals)
Adaptations to Temperature Extremes • In mammals, thermoregulation is controlled by the hypothalamus • When the temperature of blood exceeds 98.6°F, neurons in the hypothalamus detect the temperature change, stimulates its heat-losing center • Causes dilation of peripheral blood vessels, bringing more blood to the surface to dissipate heat • Stimulates sweating; suppression of metabolism-stimulating hormones
Adaptations to Temperature Extremes • When the temperature of blood falls below 98.6°F, the heat promoting center of the hypothalamus is stimulated • Causes constriction of blood vessels • Inhibit sweating • Epinephrine produced by adrenal medulla to stimulate metabolism
Adaptations to Temperature Extremes • Torpor – decrease of metabolic rate over a relatively short period of time • Reduces the need for food intake by reducing metabolism • More common in smaller animals; larger animals have too much mass to effectively cool
Adaptations to Temperature Extremes • Hibernation – drastic decrease in metabolic rate over a long period of time, in response to colder temperatures • Effective only in midsize animals • Too big; costs more energy to increase temperature than what is saved over winter • Too small: can’t store enough energy • Estivation – large decrease in metabolic rate over a long period of time, in response to hotter temperatures (& food, water supplies)
Thermoregulation • Fever – an increase in body temperature to levels above normal • Considered to be one of the body’s (normal) immune mechanisms to inhibit the growth of bacteria or viruses • Extremely high fevers, however, are detrimental and can result in seizures and hallucinations