Human Body Composition and Bioenergetics Flashcards
Describe basic body composition (4 body compartments)
Fat (20%)
Body cell mass (50%)
ECF (20%)
Structural tissues (10%)
Which compartment is the body’s chief fuel storage site?
Fat (20% of body mass)
Unlike the fat compartment, which compartment may change rapidly and drastically?
Water (ECF)
Changes in this compartment account for…??
Define the body cell mass compartment
Comprises the metabolically active tissues (except for adipocytes, which are relatively inactive).
What are the metabolically active tissues of the body (body cell mass)?
Muscle cells (80%)
Internal organs, bone marrow, blood cells and lymphoid tissues (20%)
What is a”normal body habitus”?
A traditional expression that means normal body shape and appearance.
?
Water flows between what compartments of the body?
Between body cell mass and ECF (water flows freely between these two compartments)
a) Osmotic barrier between ICF and ECF
b) Osmotic barrier within the ECF
a)
b)
The ECF can be approximated to…
an isotonic NaCl solution
Describe dehydration
* Definition
* Cause
* Danger
* Symptom
* Lab
- (Pure) water loss from the whole body (both ECF and ICF)
- Can be due to water deprivation or increased perspiration
- Dangerous: leads to cell shrinkage (esp. brain)
- Symptoms: thirst
- Lab: increased serum Na (hypernatremia)
Describe ECF volume contraction (“volume depletion”)
* Definition
* Danger
* Symptom
- Isotonic loss of water AND electrolytes from the ECF compartment
- Urgently dangerous
- Symtpoms: low BP, rapid HR, dry mouth, reduced urine volume, patient feels terrible, sunken eyes, decreased skin turgor
Describe ECF volume excess
* Definition
* Cause
* Danger
* Symptom
* Lab
How do we treat dehydration?
Replenish whole body water (both ECF and ICF), treat cause
How do we treat ECF volume contraction?
How do we treat ECF volume depletion?
True or false: Healthy people asymptomatically tolerate mild changes in ECF volume.
True: Small daily weight fluctuations are normal
The most sensitive, accurate and simple way to detect small changes in ECF
?
True or false: Adipose tissue is not fat.
True! Adipose tissue is only ~85% fat and 15% structural tissue (we can’t just have free fat in the body)
How can you evaluate a patient;s fat compartment?
? rewatch
How useful is BMI?
It remains useful for diagnosing and communicating the severity of starvation disease.
Respiration formula
3 chemical characteristics of life
- Constant temperature reactions (cannot use heat to overcome activation energy, but enzymes)
- Enzymes
- Free energy is captured
What is energy used for by cells?
To stay alive!
* To maintain ionic gradients
* To allow transport
* Synthesis/degradation
* Cell turnover
* To maintain organ function
…
Staying alive creates heat. Explain.
When glucose is combined with oxygen and oxidized, it produces CO2, water and energy, releasing heat (lost energy - 50%) and utilizable free energy harnessed into ATP (which cells use to stay alive, after which it is also lost as a heat).
External work & heat
External work does not immediately create heat, and creates it outside the body.
All the internal energy released by fuel oxidation is immediately converted to…
heat energy
In medicine and real humans, we use indirect calorimetry to measure people’s energy expenditure by looking at their O2 consumption. Describe the formula for a person’s basal metabolic rate (BMR).
BMR = Heat creation = 4.8 x oxygen consumption
RMR, BMR, REE all refer to…
energy expenditure at rest
1 RMR is equivalent to…
1 MET (metabolic equivalent of task)
Very approximately, a normal adult’s RMR will be approximately…
1kcal/kg/hour (24kcal/kg/day)
Explain:
1 MET
2 METs
3 METs
Define total daily energy expenditure
Resting metabolic rate (70%) + thermic effect of food (10%) + non-resting energy expenditure (15-25%) + …?
What is the thermic effect of food?
The amount of energy you must expend to process nutrients in a meal
Most of the RMR is generated by what body compartment?
Body cell mass
Fever: 1 degrees C rise in body temperature may increase resting metabolic rate by approximately…
1 degrees C rise in body temperature may increase resting metabolic rate by approximately 10%
When you have a fever, why does your temperature fluctuate up and down over the course of a febrile episode?
Temperature is regulated during fever, but less precisely, making temperature fluctuations cruder?
Why do we develop a fever to fight infection?
Why does a person feel cold and shivering as they develop a fever?
The setpoint is changed so that their body temperature rises…?
The best time to do a blood culture to capture the pathogens when you suspect infection?
Before the body temperature goes up (i.e. before they develop a fever and high temperature), when you notice the patient shivering and cold.
Normal body temperature
Normal range is around 37C
When body temp falls below its set point, we feel…
cold
When body temp rises above its set point, we feel…
warm
