CHAPTERS 6 AND 7 TEMPERATURE AND TEMPERATURE REGULATON

1
CHAPTERS 6 AND 7 TEMPERATURE AND TEMPERATURE
REGULATON
2
THERM DEFINITIONS

• HOMEOTHERM MAINTAINS HI BODY TEMPMUST REMAIN
  ACTIVE IN COLD SURROUNDING
• ENDOTHERMS MAINTAIN TEMP BY INTERNAL HEAT PROD.
• ECTOTHERM MAINTSINS BODY TEMP BY USING BEHV.
  ADAP. Ex. Lizard in sun

3
TEMPERATURE VS. RATES OF BIOLOGICAL ACTIVITY

• MOST ANIMALS LIVE WITHIN A ZONE OF TOLERANCE
• CHEMICAL RXN INVOLVE MOLECULAR COLLISIONS
  THEREFORE HEAT MAY CHANGE TIER CHARACTERISTICS

4
Q 10 RULE

• MEANS THE INCREASE IN RXN VELOCITY CAUSED BY A
  10 DEGREE RISE IN TEMP
• SOME EXAMPLES Q10 FOR ENZYME RXS RANGES 2-3, FOR
  COAGULATION OF HGB 13.8
• GENERAL RULE A 10 DEGREE TEMP INCREASE CAUSES 2-3
  FOLD OXYGEN USE INCREASE

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Q 10 RULE CONT

• IF THE RATE DOUBLES Q10 2
• IF THE RATE TRIPLES Q10 3
• EXAMPLE STARTING WITH A Q10 OF 2 AND ATEMP OF
  0 DEGREES C AT 10 DEGREES THE RATE WOULD DOUBLE
• AT 20 DEGREES THE RATE WOULD QUADRUPLE AT 30
  DEGREES IT WOULD INCREASE 8x

6
PHYSIOLOGIC COMPENSATION FOR RATE LIMITING TEMP
EFFECTS

• AT THE MOLECULAR LEVEL LIFE PROCESSES ARE
  GOVERNED BY Q10, THE LOGARITHMIC LAW RELATING
  VELOCITY OF RXN TO TEMP
• ANIMALS HAVE EVOLVED COMPENSATORY MECHANISM TO
  BEAT THE Q10 RULE

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TEMPERATURE COMPENSATION IN POIKILOTHERMS

• THREE TYPES OF COMPENSATION
• ACCLIMATION OR ACCLIMATIZATION
• BODY TEMPERATURE ADJUSTMENT OR REGULATION
• GENETIC OR EVOLUTIONARY ADAPTATION
• POIKS TEMP FLUCT W ENVT.

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TEMPERATURE COMPENSATION IN POIKILOTHERMS

• BIOCHEMICAL AND CELLULAR ADJUSTMENTS
• NORMALLY INVOLVES ENZYMES, PROTEIN
  STRUCTURES,WATER CONTENT OF TISSUES
• ORGANIZATION OF LIPIDS
• CONTROL OF METABOLIC TOXINS PRODUCED

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TEMPERATURE COMENSATION IN POIKILOTHERMS

• WATER CONTENT,SUPERCOOLING,ANTIFREEZE
• GRADUAL TEMP CHANGE MUCH LESS DAMAGING
• PREVENTION OF INTRACELLULER WATER
  CRYSTALLIZATION, BECOME HYPERTONIC
• ICREASE IN OSMOTIC CONTENT OF BODY FLUIDS TO
  DEPRESS FREEZING POINT

10
TEMPERATURE COMPENSATION IN POIKILOTHERMS

• GLYCEROL IS A SUBSTANCE THAT DEPRESSES THE
  FREEZING POINT OF VARIOUS SOLUTIONS BUFFER TERT
  AND QUAT. PROTEIN STRUCTURE CHANGE
• GLYCOPROTEINS ALSO
• OTHER PROTEINS ALSO OCCUR IN ARCTIC FISH
• MECHANISM THROUGH GROUPS BONDING TO DEPRESS
  FREEZING PT

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TEMP CONPENSATION IN POIKS CONT

• GYLCOPRPTOEINS MOST COMMON
• ACT BY PREVENTION OF ADDITOIN OF WATER CRYSTALS
  TO ICE LATTICE
• SEVERAL HUNDRED TIMES MORE EFFECTIVE THAN SODIUM
  OR GLUCOSE
• ALL HAVE THE AMINO ACIDS ALANINE, THREONINE, IN
  COMMON

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TEMPERATURE COMPENSATION INPOIKILOTHERMS

• LIPIDS, CELL MEMBRANES, ENZYME SYSTEMS
• DIFFERENT BODY LIPIDS MAY BE PRESENT IN ANIMALS
  IN DIFFERET CLIMATES
• INCREASING BODY TEMP DECREASES FLUIDITY OF THE
  MEMBRANES
• MOST CRITICAL AREAS ARE CELL MEMBRAMES AND
  NERVOUS TISSUE LININGS

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ENZYME ADJUSTMENTS

• ADAPTIVE RESPONSE OF ENZYMATIC SYSTEMS IS
  CRITICAL TO THERMAL RESPONSE
• ADJUSTMENTS OCCUR AT MULTIPLE STEPS OF THE
  REACTION SERIES
• TOXIC METABOLITES , HISTAMINE AND THROMBOPLASTIC
  MATERIALS OFTEN ARE FOUND IN TISUES
• MECHANISM PROBABLY DUE TO PROTEIN DENATURATION

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PHYSIOLOGIC AND BEHAVIORAL ADJUSTMENTS

• MOST POIKILOTHERMS USE BEHAVIOR TO AVOID OR
  MINIMIMIZE TEMP CHANGES
• INFARED SENORS IN FACIAL PITS OF RATTLERS CAN
  DETECT .001 - .005 DEGREE C DIFFERENCE
• BASKING IN SUNSPOTS

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PHYSIOLOGIC SDJUSTMENTS

• CARDIOVASCULAR ADAPTATION
• CUTANEOUS VASOCONSTRICTION IN COLD VASODILATION
  IN HEAT IN POIKS
• AMPHIBIANS MAY SALIVATE IN HEAT, OR DO
  EVAPORATIVE COOLING

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PHYSIOLOGIC ADJUSTMENTS

• NEUROENDROCRINE
• IN POIKS, APPEARANCE OF ANTIFREEZES AS WINTER
  APPROACHES
• THIS IS TIMED BY PHOTOPERIOD IN ARCCTIC TELEOST
  FISH
• APPEARS IN FALL, PITUITARY SIGNALS CHEMICAL
  CLEARANCE IN SPRING

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BODY TEMP BIRDS AND MAMMALS

• THERE IS A CORE BODY TEMP AND A PERIPHERAL TEMP
• DURING EXERCISE THE BBBDOY TEMP MUST ADJUST TO A
  10 FOLD RISE IN HEAT PRODUCTION
• BODY TEMP FOLLOWS LIGHT CYCLE , DIURNAL
  FLUCTUATION

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PHYSIOLOGIC ADJUSTMENTS

• CAPACITY FOR ENDOTHERMY
• MAINTANENCE OF RELATIVE CONSTANT BODY TEMP
• SOME TUNAS AND SHARKS DO THIS VIA OPERATION OF
  THERMAL EXCHANGE UNITS

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PHYSIOLOGIC ADJUSTMENTS

• TYPES OF HEAT EXCHANGERS ( LOCATED IN TRUNK HEAVY
  MUSCLES)
• CUTANEOUS OR LATERAL RETIAL
• SERVED BY A CUTANEOUS ARTERY AND VEIN
• IN BLUEFIN TUNA AND LAMNID SHARKS

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PHYSIOLOGIC ADJUSTMENTS

• TYPES OF HEAT EXCHANGERS
• CENTRAL OR HEMAL RETIA
• SUPPLIED DIRECTLY BY DORSAL AORTA
• IN SKIPJACKS

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PHYSIOLOGIC ADJUSTMENTS

• PRINCIPALS FOR USE OF HEAT EXCHANGERS
• REGARDLESS OF TYPE THEY ARE ELABORATE RETE
  MIRIBLES, USING COUNTER CURRENT FLOW
• BLOOD FLOW IS VERY SLOW THROUGH SUCH AREAS
• COLD BLOOD IS HEATED BY ACTIVELY METABOLIZING
  TISSUES

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HOMEOTHERM TEMPERATURE COMPENSATION

• CRITICAL TEMPERATURE ( HOMEOTHERMS) IS THE LOWEST
  AIR TEMP AT WHICH AN ANIMAL CAN MAINTAIN RESTING
  OR BASAL METABOLIC RATE WITHOUT LOWERED CORE
  TEMP.
• IN MAN THIS TEMP IS 27-TO,25 DEGREES CENTEGRADE
• IN ARCTIC FOX -30 TO -40

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HEAT PRODUCTION

• IN HOMEOHERMS A MARKED INCREASE IN MUSCLE TONE
  AND MUSCULAR ACTIVITY PRECEEDS SHIVERING.
• MUSCLES GENERATE HEAT SHIVERING THERMOGENESIS
• GENERATION OF HEAT BY METABOLIC PROCESES AND
  ORGANS NON-SHIVERING THERMOGENESIS

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HEAT PRODUCTION CONT

• ANIMALS VARY IN CAPACITY TO GENERATE HEAT
• IN SOME MAMMALS CATS, RATS, DOGS AND SHEEP BASAL
  METABOLIC RATE IS HIGHER WHEN THEY ARE COLD
  ACCLIMATED

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BROWN FAT SPECIAL THERMOGENIC TISSUE (MAMMALS)

• MOST EVIDENT IN NEWBORNS, HIBERNATORS, AND COLD
  ACCLIMATED MAMMALS
• RESPONDS TO COLD STRESS BY PRODUCING HEAT BURSTS
• LOCATED IN NECK AND THORACIC REGIONS NEAR LARGE
  VESSELS FOR QUICK HEAT TRANSPORT
• STIMULATED BY NORADRENALIN

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BROWN FAT CONT

• NORADRENALIN BINDS TO BETA RECEPTORS ON PLASMA
  MEMBRANES OF FAT CELLS
• THESE CELLS HAVE 150,000 OF THESE RECEPTORS MUCH
  HIGHER THAN IN OTHER CELL TYPES
• CATECHOLAMINES AND CYCLIC AMP PROMOTE RAPPID
  LIPOLYSIS
• SOME OF THE FATTY ACIDS ENTER MITOCHONDRIA FOR
  IMMEDIATE USE

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BROWN FAT CONT

• SOME FATTY ACIDS EXPORTED FROM CELL MECH STILL
  NOT CLEAR
• HEAT PRODUCTION IS THE ONLY FUNCTION OF BROWN FAT
• IT IS VERY VASCULAR WITH HIGH CONCENTRATIONS OF
  CYTOCHROMES, MYOGLOBIN
• HAS HHIGHER CONCENTRATIONS OF WATER, PROTEINS,
  CHOLESTEROL, MITOCHONDRAIL ENZYMES

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HEAT LOSS

• CONSTANT BODY TEMP REQUIREMENT HEAT LOSS HEAT
  GAIN
• CONDUCTION TAKES PPLACE WHEN PHYSICAL SUBSTANCES
  ARE IN DIRECT CONTACT
• CONVECTION HEAT MOVEMENT IN FLUIDS
• RADIATION HEAT TRANSFER IN ABSENCE OF DIREST
  CONTACT

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HEAT LOSS

• NORMALLY VIA CONDUCTION, RADIATION, VAPORIZATION
• IN AQUATIC ENVIRONMENTS CONVECTION MAY ACCOUNT
  FOR ENTIRE HEAT TRANSFER
• TERRESTRIAL ORGANISMS NORMALLY LOSE MOST HEAT BY
  RADIATION
• IN SMALL BIRDS EVAPORATIVE COOLING MAY BE THE
  MAJOR MECHANISM

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CONTROL OF HEAT DISSIPATION FUR AND FEATHERS

• ARCTIC SPECIES BETTER INSULATED THAN TROPICAL
• ANIMALS THAT LACK FUR CAN OBTAIN INSULATION VIA A
  COLD SKIN LAYER( PIGS)

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COUNTERCURRENT EXCHANGERS

• EXTREMETIES ARE OFTEN HEAT LEAKERS NOT WELL
  INSULATED
• THESE MUST BE COLD RESISTANTAND ABLE TO TOLERATE
  TEMP CHANGES
• EX CARIBOU LEG AT 8 DEGREES BODY AT 37 DEGREES
• COUNTER CURRENT EXCHANGERS MAJOR ARTERIES
  SURROUNDEDBY THIN WALLED VEINS IN APPANDAGE

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COUNTERCURRENT EXCHANGERS

• WHEN HEAT IS TO BE CONSERVED PERIPHERAL
  CIRCULATION IS RESTRICTED
• WHEN HEAT DISSIPATION IS NEEDE VASODILATION
  OCCURS
• USED IN MANY MAMMALS

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HEAT LETHAL MANIFEATATIONS

• HIGH TEMP DEATH DUE TO
• DENATURATION OF PROTEINS
• THERMAL ENZYME INACTIVATION
• INADEQUATE OXYGEN SUPPLY
• EFFECTS ON Q10 DEPENDENT MET. RXNS
• TEMP EFFECTS ON MEMBRANE STRUCTURE

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ACCLIMATION AND ACLIMATIZATION

• ACLIMATIZATION OCCURS SEASONALLY, AADJUSTMENT TO
  TEMP CHANGES WITH CLIMATE CHANGE USUALLY UNDER
  INFLUENCE OF PHOTOPERIOD
• ACCLIMATION , WHEN ORGANISM ADJUSTS TO
  ARTIFICALLY IMPOSED CONDITION, USUALLY IN THE
  LABORATORY

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THERMAL ACCLIMATION

• OFTEN AMINALS DO NOT FOLLOW THE PATTERN
  PREDICTED BY THE Q10 RULE DUE TO PHYSIOLOGIC
  COMPENSATORY MECHS
• BE SURE TO READ THIS IN YOUR BOOK

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HIBERNATION TORPITIDY ESTIVATION

• HIBERNATION BODY TEMP DROPS, HEART AND METABOLIC
  REATE DROP, ANIMAL IS TORPID SHOWS LITTLE
  RESOPNSE TO ENVIRONMENTAL STIMULI
• NORMALLY DURING WINTER, AT LOW TEMP
• ESTIVATIONINACTIVITY DURING SUMMER MONTHS
• SSOME ANIMALS AND BIRDS, LIKE HUMERS GO INTO
  TORPID STATES OVER NIGHT, DUING TIME SWHEN FOOD
  IS LIMLITD