Energy Expenditure And Temperature Flashcards
Caloric Theory
Heats consists of a self-repellent fluid (“caloric”) that can be transferred from one body to another, but cannot be created or destroyed.
Caloric Theory was superseded by
the mechanical theory of heat
Lavoisier and LaPlace Calorimeter (1780)
Placed animal in chamber with insulation all around it (insulated from outside environment). Air flow, packed with ice. Experiment evaluated amount of heat produced by the mouse (measured by amount of ice that melted into water). 80 kcal of heat melts 1 kg of ice. How do you measure thermal production Measure heat based on what it does to ice Body heat of guinea pig melts ice Ice into an isolated chamber it wont melt but if you add a guniea pig its body heat will melt. Air needs to be able to enter and exit. Heat only leaves the chamber because of ice melting and then you measure the amount of water collected and get heat.
Heat according to caloric theory is similar too
phlogostin
Joules work on heat
Theoretical experiment: Chamber mixed with water. Drop a 427 kg weight from height of one meter. Transfer of energy into spinner. When weight falls, will raise temperature by 1°C. 427 mkg work → 1 kcal heat. 427 mkg = 1 kcal heat mechanical energy → 0.56 g (mechanical) give 1 kcal chemical energy → 0.465 x 10-10g = 1 kcal nuclear energy 1 BTU = 1 lb water raised 1°F = 252 calories Calorie = energy it takes to increase the temperature of one gram of water by 1°C Conversion between Joules and calories: 1 calorie = 4.1833 Joule
427 mkg
1 kcal heat mechanical energy
0.56 g (mechanical) give
1 kcal chemical energy
0.465 x 10^-10g
1 kcal nuclear energy
Conversions
427 mkg = 1 kcal heat mechanical energy → 0.56 g (mechanical) give 1 kcal chemical energy → 0.465 x 10-10g = 1 kcal nuclear energy
1 BTU
1 lb water raised 1°F = 252 calories A lb is half a liter but 1 degree farenheight is about half a degree centigrade 1 btu equals approx 1 kilojoule
Calorie
energy it takes to increase the temperature of one gram of water by 1°C
Conversion between Joules and calories:
1 calorie = 4.1833 Joule
kcal
food calorie which equals 1000 small calories which equals 4186 joules
Joules unit conversion
1 J = (kg x m^2)/s^2 = N x m = W x s = Pa x m^3 = C x V
Specific heat of water:
1 calorie = 4.1855 J = “15° calorie” (14.5°C → 15.5°C, typical calorie) 4.184 J = “thermochemical calorie” (0°C → 1°C) - physiologist use this one 4.190 J = “mean calorie” (0°C - 100° C) (avg energy to move 1 g of water 1 C)
Resting Metabolic Rate
70 kcal/hour 250 mlO2/min 85 Watts
Exercise Increases the RMR
400-600 kcal/hr – 5x increase in calorie/heat production along with rr/circulatory rates and o2 consuption and is pretty constant across mid range mammals.
Athletes and Thouroghbreads
Athletes and thoroughbread horses can go from 10-20x RMR during exercise They have a lower resting rate and a larger maximum rate
Shivering increases energy production by
400%
Q10
relationship btw enzymatc activity at 2 different temperatures in bio tissues q10 is 2 meaning for an increase of 10 degrees activity will double. We use it in the other direction to lower in kids we can go really low. A 20 degree drop in temperature reduces the rmr by 4
Carbs and Protein
4 kcal/gram
Alcohol
7 kcal/gram
Fats
9 kcal/gram Fats are the most concentrated form
To maintain body weight you need
15 cal/lb (RMR)
A 200 lb person would need to eat how many calories per pound to maintain his weight
15 calories/lb so about 3000 calories to gain or lose weight
3500 kcal/lb to
gain or lose weight - dependent on water balance
Most of metabolism is set to
gain weight i.e. increase fat stores for leaner times
Exercise increase skeletal muscle and rmr by
Exercise increase skeletal muscle and rmr by 5x so contribution decreases for these 5 and increases for skeletal muscle reduce for these 5 and increase
Exercise increase skeletal muscle and rmr by
Exercise increase skeletal muscle and rmr by 5x so contribution decreases for these 5 and increases for skeletal muscle reduce for these 5 and increase
Brain
2 percent body mass uses 20% energy, blood, O2
Ratio of central nervous system to body metabolism in vertebrates
Mink et al Am J Physiol 241:R203-R212, 1981 most vertebrate species use 2-8% of their basal metabolism for the central nervous system (CNS). “of all animals, man has the largest brain in proportion to his size,”- Aristotle Domesticated animals use less (bred for size and dumbness?) <2% Primates use more (>10%); also mouse 8.5%; but shrew 1.5% Very large animals also low; ostrich 0.7%, elephant 2.0%, whale 0.5% Humans need to use less of their brain to take care of them selves percent is how much of their energy used to support CNS more energy used for your brain less function
Mechanical Work is
easily defined physiologically using muscles
Chemical Work
is difficult to define but is used in assumptions to quanitfy the work done by the brain Moving ions, neurotransmitters (nerve cells) Establishing “batteries” = energy stored in ion gradients Mitochondrial “fuel cell” to recharge batteries Work defined by energy expenditure by muscles Brain is hard to relate to the physics of work – most chemical work – use energy based on ATPase and pumps and how much work done to make the pumps work
Brain O2 consumption
1.5 umol/g/min = 3.5 ml/100g/min
70 Kg Man has ____ Kg brain
1.4 Kg brain
Brain consumes ______ O2/day
Brain consumes 3 Moles O2/day 67L O2/day = about 15 balloons
Brain makes ______ water per day
6 Moles of water per day (18 g/M, 18 mL/M = 108 mL H2O/day)
The brain Makes ______ Moles of ATP
Makes 18.12 Moles of ATP (~9 Kg; 20 lb) / day 7mM/min = 10 M ATP a day;
In an Normal Young Adult Male Cerebral Blood Flow is
57 ml/min/100g of brain tissue 798 ml/min/total brain (1400 grams) Brain about a liter a min bec 1/5 co and co 5 liters is led bulb about as efficient as mito
In an Normal Young Adult Male Cerebral O2 consumption is
3.5 ml/min/100g of brain tissue 49 ml/min/total brain (1400 grams)
In an Normal Young Adult Male Cerebral glucose utilization is
5.5 mg/min/100g of brain tissue 77 mg/min/total brain (1400 grams)
brain uses energy
in small burst rather than one shot like most energy production
The 10% Brain Myth
Humans only use 10% of their brain and if we use more of it at one time we can increase our mental abilities it is false
Proof 10% Brain Myth is False: Energy
- Look at the energy!!! Resting brain metabolism is 2 times that of brain with suppressed activity Maximum cerebral metabolic rate is about 2.5 times resting metabolism Metabolic scope is thus about 5. Thus, at rest the brain is using using about 20% of our useful energy capacity, Rmr – darkned room 50 ml/min Zero activity – 02 is half 25ml/min Comp activate – seizure – increse by 2 times ½ to 2 and a 1/2 gives the 1/5 ratio
Proof 10% Brain Myth is False: Full Activation
- Full activation, all nerve cells firing at once is non-functional (represented by status epilepticus. So, for best brain function focus narrows the number of nerve cells used at any one time. - Focal and Local
Brain Use Facts: Truths
- There is no part of the brain that is not used at some time or other. 2. There is some activity in every part of the brain at all times 3. The brain uses a lot of energy. If 90% were unnecessary there would a large survival value to smaller, more efficient brains. Brains. An inefficient brain would be unlikely to evolve. 4. Because of the constraints of the female pelvic opening and the difficulties of childbirth due to a large brain with large skull, evolutionary pressure would select against a brain where 90% of the mass is redundant.
Metaphor
Brain as a piano 88 keys use all keys at some point but only use 10 keys at any one time
Brain Energy Consumption
20% of cardiac output goes to the brain; 20% of O2 consumption of the body at rest comes from the brain. Flaming marshmallow analogy → oxidation of glucose (in brain, happens in steps as opposed to continuously)
Temperature, RMR, Life Span
Low temperature environments - decrease RMR and increase life span
Homeothermy vs Poikilothermy
Regulation of internal body temperature
Homeothermy
Regulation of internal body temperature
Poikilothermy
Internal body temperature varies
Endothermy vs Ectothermy
Regulation by exchange with environment
Endotherm: internal heat generation mechanisms
Ectotherm: environment causes temperature changes
Endothermy
produce heat to control body temperature - warm blooded
Ectothermy
Use ambient temperature to control blood temperature with very little or neglibile heat production - cold blooded
Warm Blooded vs Cold Blooded
Set point vs relative temperature
Human enzymes optimized to work at body temperature
Other enzymes can work at variable temperatures
Dinosaurs have trouble cooling off due to size
Average Temperature of Mammals
37-38ºC
Average Temperature of Birds
39-40ºC
Average Temperature of Marsupials
36ºC
Average Temperature of Monotremes
31ºC
They are homeotherms and endotherms
Temperature Facts
Birds evolved from dinosaurs Advantage constant temp – effient enzymes at that range Higher temp – more efficient metabolism – need to eat more
Modes of Heat Transfer
Conduction – needs something to carry it – occurs when objects are in direct contact Convection – via fluid from hot to cold needs contact
Radiation - waves
Evaporation – water changing state
or
Conduction: requires contact
Convection: carries by another fluid i.e. air or water
Radiation: electromagnetic energy
Evaporation: water evaporating from skin, endothermic to cause cooling
Heat Balance Equation
Modes of Heat Transfer Equations
A lot of this is based on gradients all from ficks law of diff gradients are impt for energy
Van’t Hoff relation & Physiological Q10
Svante Arrhenius (1859 – 1927)
Arrhenius used absolute temp and co2 variations and climate changes
Surface Law / Surface Rule
§Heat loss is from the surface, small animals have increased S / V and so have increased heat loss which must be balanced by increased metabolic heat production to keep warm
Smaller u r the more heat u lose so smaller higher met rate
Heat loss proportional to surface area – E C and R are directly proportional to surface area
Heat production is a function of mito volume
Animal smaller volume is bigger
Larger animal produce more vol wise but smaller area to get rid of it
Area to vol is 3 to 2
Bergmann’s Rule
1847
Warm blooded animals in colder climates are larger in body size than relatives in warm climates
Heat loss related to surface area
Heat production is related to volume/mito
Some wiggle room
Small animal loses heat faster than a large animal, needs higher metabolic rate in order to keep warm
Hypothesis: lose less heat because of the surface-to-volume ratio
Easier to keep warm with larger body size
Equatorial vs temperate
Body Temp, RMR, and Life Span
Decrease body temp live longer bec lower met rate
Lower met rate increase lifespan
Increase body size increase life span but lower met rate
Lower met rate increase life span
The relation of body weight to metabolic weight and organ size
Study in mice
Reduction of core body temperature resulted in an extended lifespan
Lower metabolic rate = greater lifespan
