Jan30 M2-Bioenergetics Flashcards
TBW, ECF and ICF % of body weight
60%
ECF 20%
ICF 40%
what determines the volume of a compartment and how water diffuses between them
- number of osmotically active particles
2. intravascular hydrostatic pressure
osmole def
osmotically active particle, so a particle that can’t cross a water permeable membrane
5 naturally-occuring molecules that freely and passively penetrale cell membranes (so are not osmotically active)
water, O2, CO2, urea, ETOH
IC and EC protein concentration
200g per L IC
70g per L EC
low conc ions and high conc ions in the cell
low: Na and Cl
high: K, Mg, PO4
serum def
sample of blood without the blood cells and precipitated coagulation factors
typical % blood cells in the blood + blood volume and plasma volume of 70 kg indiv
blood is 40% blood cells
70kg indiv.: 5L blood, 3L plasma
volume ratio between IV and IS compartments + reason
IS 3-4 times size of IV bc of balance of hydrostatic and colloid P
speed of osms equilibration ECF-ICF vs ECF-IV
ECF-IV very fast because IS is 0 P compartment (capacitor) to buffer fluctuations IV
ECF-ICF takes hours
dehydration def
ECF hypertonicity and loss of ICF water
main 2 reactions to dehydration and why
- thirst (pituitary senses ECF osmolarity)
- reduction in urinary free water excretion
common causes of dehydration
lack of water, lack of water + meds increasing urine water loss, neuro prob: no thirst, big loss of water, other diseases (nephro bloc)
volume depletion def and cause
ECF volume depletion. loss of iso-osmolar electrolytes and water from ECF (diarrhea, vomiting, etc.)
how to check for volume depletion
- absence of JVP, veins of lower arms and hands not filled with blood
- HR, BP and how these change with position change
- skin pinch= it’s not elastic
- dry mouth
- urine output
- dry diaper
where volume is lost in volume depletion
in both ISF and IVF (and more in ISF), except if trauma, splenic rupture or acute hemorrhage)
shock and pre-shock def
shock: more than 50% IV volume loss
pre-shock: more 15% IV volume loss
pre-shock charact.
very low BP, very high HR, veins collapsed, urine output is 0, patient feels terrible
Third space disease
ECF (or whole blood if hemorrhage) spills deep within the body (picture of hypovolemia but no indication of issing ECF, like hemorrhage or diarrhea)
best way to detect ECF volume expansion (and best way for ECF volume depletion too)
monitor patient’s body weight over time
signs of ECF excess
edema (skin, lower extremities)
severe and everywhere is anasarca
most common condition leading to an excess (beyond tolerable) IV expansion
right heart failure (pulm edema, high venous P, edema)
potential spaces and name of edema in there
pleural space, pericardial cavity, joint space, abdomen (ascites). these are called effusions
severe toxic-inflammatory states (severe injury or infection): effect on water balance
increase capillary wall permeability to HMW proteins
transudate def
effusion with normal IS fluid and low protein (high outward hydrostat P, negative IS tissue pressure, low plasma oncotic P)
exudate def
protein-rich, cell-rich, outpouring of inflammatory fluid at infection or damage site
important modifiable determinant of ECF volume
dietary sodium consumption
4 anatomic compartments and %
fat 20%
BCM 50%
ECF 20%
Structural tissues 10%
body cell mass def
metabolically active non-fat tissues
structural tissues def
skeleton and associated CT
technique to determine fat to total body weight and principle
densitometry.
100% fat body would have density of 0.900
0% fat body would have density of 1.100
fat content vs visible tissue
fat content with body composition technique is pure fat
fat seen on physical exam is adipose tissue (85% fat)
what is stored in adipose tissue
triglycerides
to lose 1kg of pure fat, how much adipose tissue must be lost
1.18kg (1/0.85) bc only 85% adipose tissue is pure fat so need more than 1kg of adipose tissue
2 ways to check body fat content clinically
BMI and physical exam
BMI formula
weight (in kg)/height (m)2
BMI range for normal body fat
18-25. below 18, fat low. over 25, fat high
problem with BMI over 30
increased health risk, and increases with higher BMI over 30
adipocytes vs BCM metabolic activity
adipocytes: very low
BCM: account for most of REE
what makes up the BCM
80% skeletal muscle
15% liver kidney spleen intestines lungs heart etc
severity of BCM losses
10% loss = lose strength/derangements
25% loss = severe disability
45% loss = very dangerous, can’t live
easiest/fastest way to assess BCM clinically
examine patient’s muscles
ways changes in BCM can be calculated
-determining rate of protein intake and rate of a.a being catabolized and their N being excreted
values to know in calculating the BCM change (3)
- N makes up 16% of protein weight (1g N lost = 6.25g protein lost)
- 1g protein lost = 5g weight lost bc 4g water coming with it
if one is losing 15g N/day, what’s the calculation for finding daily BCM loss
15N/day x 6.25g prot/g of N x 5g mass/g prot = 469 g BCM
time scale of changes in adult skeletal mass and def of skeleton mass
bones and CT
adult skeletal mass lost over months/years
homeostasis def
rate of gain and loss of all body constituents are in dynamic regulated balance
essential nutrient def
nutrient essential for health
nonessential nutrient def
not required for health because 1) another nutrient can do the same fct OR 2) body can synthesize it from another nutrient
4 nutrient classes
lipids, carbs, proteins, ethanol
3 levels of organization of metabolic fcts
cellular, whole body, external work done
energy units and their definition (unit of our interest)
kcals. heat energy needed to make 1L of water raise its temp by 1 degree
where exactly energy from food is stored
high-energy phosphate bonds (synthesis of ATP from AMP and ADP)
body ATP content and how much times it takes to burn it
45g. all burned in 1 min so complete ATP turnover takes 60s
during supra-maximal exercise, what does the body do to adapt to the failling intracellular ATP
activates a reg pathway that accelerates a lot the anaeorobic glycolysis
Pasteur effect def
accelerated glycolysis in anaerobic conditions
why lactic acid made during exercise
anaerobic glycolysis makes NADH. if O2 lacking, can’t make it NAD+ so the highly reduced environment (NADH) makes pyruvic acid become lactic acid
how lactic acid turned back into pyruvic acid
when O2 back, NADH oxidized to NAD. less reduced environment so can make pyruvic acid from lactic acid
lactic acidosis def
accum of lactic acid in tissues and blood in anaerobic conditions
VO2 max
maximum rate of O2 uptake with increased lactin acid conc
energy balance: excess input vs excess output
input > output = store TGs in adipose tissue
output > input = take TGs from adipose tissue and oxidize them
positive vs negative energy balance and how to measure it
negative = output more than intput on long term. (losing weight)
compare weight at diff moments to see how balance is (neutral, positive, negative)
direct calorimetry def
technique of measuring body’s rate of heat production to measure its rate of fuel oxidation
heat combustion of the various fuels (TGs, carbs, proteins, ethanol)
TGs= 9kcal per g
carbs= 4
prots=4
ethanol=7
indirect calorimetry
get rate of fuel oxidation of the body from rate of O2 uptake (rather than from rate of heat prod as in direct calorimetry)
heat production and O2 consumption conversion rate and units
heat production (in kcal per min) = 4.8 x O2 consumption (L per min)
3 determinants of energy flow in the body
- REE or BMR
- thermic effect of food (heat from food metabolic processing)
- energy expended for activities (external work)
external work (3rd determinant of E flow) definition and diff from internal work
- conversion of chemical energy or our body into other form of energy (mechanical for ex)
- internal work in our body all converted to heat
other determinants of energy flow in disease
stuff that increases body’s metabolic rate (tissue damage, infection, inflammation, emotions)
REE or RMR or BMR % of daily total energy expenditure and what can change its value
2/3
variabilities in value come from differences in BCM composition
how to estimate one’s BMR (or REE)
1 kcal/kg/hour in men
0.95 kcal/kg/hour in women
why can’t use HB (Harris-Benedict) equations of REE estimation for obese people
bc equations limited to normal body composition.
otherwise, overestimate their REE because in reality, their fat isn’t as metab active as the rest
thermic effect of food in numbers
8% of food caloric content is spent in energy to process this food
2 major types of physical activity
- formal exercise
2. nonexercise activity thermogenesis (NEAT)
METs definition
unit of energy expenditure expressed in kcal per min (or kcal per day)
when to use METs unit
for ex, if know someone is using 3 kcal per min (light yard work, carrying groceries), would say they are using 3 METs
how to calculate TEE (total energy expenditure) (daily)
1.5 x REE
what can change body weight in short vs long term
short term: fluid intake changes, urinary excretion, sweating, evaporation
long term: BCM or adipose tissue changes
things that increase BCM and things that decrease it
increase BCM: exercise (more muscle mass)
decrease BCM: inactivitiy (muscle atrophy), starvation, cachexia, sarcopenia (loss muscle mass with age)
things that increase fat mass and things that decrease it
positive energy balance increases it
negative energy balance decreases it
how hypothalamus maintains fix body temp
signals to adjust rate of heat production (fuel oxidation, muscle activity) and heat loss (shivering, muscular activity) + feeling of hot or cold
how higher temperature is achieved (ex in fever)
oxidizing fuel at faster rate and generating heat faster than normal
2 determinants of body temperature
rate of heat generation (fuel oxidation) and rate of heat dissipation
what influences rate of heat dissipation
patient’s surface area, thermal insulation (skin, fat, clothing, ..), ambiant room temp, capacity to perspire
important mechanism for heat elimination and when is it blocked
water evaporation bc consumes heat. blocked in anticholinergics that inhibit perspiration
how BMR changes with body temp
1.1 fold increase with every rise of 1C
BMR of person with 40C fever and with usual BMR of 2000
2000 x 1.1 x 1.1 x 1.1
