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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