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General Physiology
Thermo Relations Test 2
| Environmental (ambient) temperature | principal determinant of MR -influences energy demands |
| Temperature influences | functional properties of tissues -enzyme performance, diffusion rates, viscosity of cell membranes -affects molecular conformation which is a functional state of molecule |
| Temperature affects | entire ecosystems determine geographic range correlates with biodiversity |
| Thermoregulation | regulation of a constant tissue temp |
| Classified by Tb variation Poikilotherms | have variable body temps -thermoregulate by behavior |
| Classifies by Tb variation Homeotherms | maintains a relatively constant body temp -thermoregulates via physiological processes as well as behaivior |
| Classified by heat source Endotherms | animal warmed by its metabolic production of heat |
| Classified by heat source Ectotherms | thermal conditions outside of the body determine body temp |
| What is temperature | a measure of speed of the random motions of atoms and molecules |
| What is a form of energy | heat: dependent upon both the # of atoms and molecules as well as speed of each -always moves from region of high to low temp -transfers heat energy b/w objects thermal equilibrium: when heat does not tend to move b/w objects |
| Heat transfer with environment 4 mechanisms | conduction convection evaporation thermal radiation *may gain heat from 1 mechanism while losing through another |
| Factors might influence heat exchange | surface area insulation environment temp body temp |
| Heterothermy | difference in thermal relations from one time to another, or one body region to another, w/n an individual |
| Temporal heterothermy | change in Tb related to time -hibernation |
| Regional heterothermy | difference in temp among different body parts -limbs vs. torso |
| Conduction | transfer of heat through a macroscopically motionless object -heat diffusion |
| factors affecting conduction rate | difference in temp type of material thickness of material |
| Convection | heat transfer by macroscopic motion of a substance -requires fluid flow (wind, water) -much faster than conduction |
| Convection rate dependent on | fluid speed animal orientation morphology temp difference |
| Evaporation | change of water from liquid to gas carries considerable heat |
| Latent heat of vaporization | amount of heat required to vaporize water -570-595 cal per gram |
| Thermal Radiation | -all objects emit electromagnetic radiation -rate of exchange dependent upon SA and surface temp |
| Poikilothermy | aquatic poikilotherms have body temps that are same as water terrestrial poikilotherms do not always have the same body temp as the air |
| Behavioral thermoregulation | maintain relative constant body temp through behavior ex. fish moving through columns of water |
| Eurythermal | function over a wide range |
| Stenothermal | have comparatively narrow functional Tb ranges |
| Poikilotherms must be.. | thermal generalists: able to function at different temps |
| Acute response to temp | MR of a poik is approximately an exponential function of Tb related to -activation energy -enzyme reaction rates (turnover, substrate binding) |
| Temperature coefficiant Q10 | describes the exponential relation b/w rate and temp when temp changes by 10 Q10= Rt/R(t-10) high Q10=more stress on organism during temp change/more affect on physiology |
| Compensation -Partial compensation | tendency for a trait to return to original function even though a new environmental pressure persists -if the rate does not return fully |
| Acclimation | can influence response to temp by compensation cells modify the amounts of rate limiting enzymes -increase membrane permeability by channel modulation and % saturate fatty acid chain cold temps mean more enzymes |
| Rate temp relationships Pejus (optimal) temp | point at which performance is at its best -increase in temp after pejus will decrease performance (denatures enzyme) |
| Evolutionary changes to preferred body temp | tissues are specialized for optimal performance at a temp that is behaviorally help relatively constant -enzyme substrate affinity -modified molecular forms distinct to functional temps -catalytic rate changes -membrane fluidity |
| membrane fluidity | warmer temp increases degree of hydrocarbon saturation |
| Modified molecular forms distinct to functional temps | temp affects molecular conformation and conformation affects function |
| Catalytic rate changes | colder temps make a faster turnover rate due to amino acid disparities outside of active site |
| Enzyme-substrate affinity | determines how readily a molecule will form an enzyme-substrate complex |
| Intracellular vs Extracellular freezing | intra-FATAL extra-TOLERATED |
| Response to freezing conditions | behavioral:avoid condition |
| 3 physiological mechanisms to freezing | -supercooling -tolerance to freezing -antifreeze |
| Supercooling | aqueous solutions remain unfrozen below freezing points |
| Tolerance to freezing | intolerant-die if they freeze -employ antifreeze and supercooling tolerant-can survive freezing of extracellular body water and typically freeze |
| Antifreeze | dissolved substances that are added to body fluids to lower freezing point -colligative: lower freezing point by adding more solutes -noncolligative: molecules suppress ice growth by interfering with chemical bonding |
| Homeothermy | MR rises in cold and hot environments metabolically expensive -More so in small homeotherms -An explanation for why MR is higher in homeotherms |
| Thermoregulation in homeotherms | Modulation of metabolic rate below TNZ (thermoneutral zone) |
| acute responses of thermoregulation thermogenic mechanism | Shivering – rapid unsynchronized muscle contraction/relaxation Nonshivering thermogenesis (NST) Break down of brown fat releases heat |
| acute responses of thermoregulation | Modulating insulation Pilomotor response (goosebumps) Alters thickness of motionless air around the animal Postural response Alters amount of surface area exposed to ambient air Vasomotor response Alters rate of blood flow to skin |
| Thermoregulation and appendages | Surface area to volume ratio creates issues with heat loss in appendages |
| Regional heterothermy | Some animals allow appendage to cool to conserve heat -Minimizing difference between Ts and Ta minimizes loss -Tissues in appendages typically have low metabolic demands (i.e., tendons, ligaments, bone) -Appendages can also release excess heat |
| Countercurrent heat exchange | -Depends upon two close fluid streams flowing in opposite directions -Minimizes heat loss to environment, warms venous blood |
| Thermoregulation Above TNZ | Cycling of body temperature Hyperthermia Active evaporative cooling |
| Cycling of body temperature | Allowing the body temperature to rise and fall within a day -Heat stored during day is released at night nonevaporative cooling |
| Hyperthermia | allowing the body to rise to high temps Impedes heat gain by decreasing TA- TB |
| Active evaporative cooling | increasing the rate at which evaporation occurs Sweating, panting, gular fluttering Cost: loss of water |
| Thermoregulation of the brain | Brain is less tolerant to temperature changes Countercurrent heat exchange is used to cool arterial blood to the brain Rete – an intermingling of tiny vessels that aid in thermoregulation |
| Homeotherm acclimatization to seasons | Peak MR Metabolic endurance Insulatory acclimatization |
| Peak MR | Increase in rate of heat production through metabolism |
| Metabolic endurance | Increase duration that a high MR can be maintained |
| Insulatory acclimatization | Change in pelage or peripheral blood flow reduces heat loss |
| Evolutionary changes | Homeotherms in hot climates have lower BMRs Artic species have better pelage insulation Artic species have lower-critical temperatures lower than tropical →broader TNZ Increase MR proportionately less above BMR when below TNZ |
| Escaping the demands of homeothermy | Controlled hypothermia – allowing the body temp to fall Tb approximates Ta Daily torpor – only part of a day Estivation – several days or longer during summer Hibernation – several days or longer during winter |
| Lowering Metabolic Rate | Biochemical downregulation body temperature falls Q10 effect Can drop MR to 25% of BMR |
| Warm bodied fish | Some fish are endothermic and homeothermic Tuna, lamnid sharks, billfishes Swimming muscles are active enough to generate heat Must impede heat loss from region or it will be lost through gills Countercurrent heat exchange with rete |
Created by:
epannell
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