Transcript Energy Metabolism Body Temperature Instructor: Ge Shun Department of Physiology Jining medical college Office: 0850 physiological sciences Email: [email protected].

Energy Metabolism
Body Temperature
Instructor: Ge Shun
Department of Physiology
Jining medical college
Office: 0850 physiological sciences
Email: [email protected]
Metabolism
Material metabolism
Energy metabolism
Material metabolism
Chemical reactions
Anabolic reactions
Catabolic reactions
Anabolism and
catabolism are
two opposing
activities
taking place
simultaneously
in the cell.
Laws of Thermodynamics
1st law- Energy cannot be created or destroyed.
2nd law- Some usable energy dissipates during
transformations and is lost.
I fought the law & the law won
• To summaries:
• The 1st law says that we can not get more
work of something then we put in and the
2nd law says we can’t even break even
Energy sources
• Carbohydrate—mainly glucose
• 65% of total energy
• Glycolysis and citric acid cycle
Energy sources
• Fat – fatty acids
• The storage of fat in the
body is much greater
than that of glucose.
• The energy liberated by
oxidation of 1g of fat is
2 times that produced
by the same amount of
glucose.
Energy sources
• Proteins
• The amount of energy privided
by proteins is relatively small
in human being.
• Protein will become the major
energy source to maintain the
essential vital activities in
special conditions.
ATP: “Energy Currency”

ATP (Adenosine Triphosphate)
It is a labile chemical
compound that is
present in the
cytoplasm and
nucleoplasm of all
cells.
ATP: “Energy Currency”
• ATP is generated by combustion of
carbohydrates, fats and proteins
• Energy from ATP can be used by the cells
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Synthesis and growth
Muscular contraction
Glandular secretion
Nerve conduction
Active absorption
CREATINE PHOSPHATE (CP )
For short term,
high rates of
energy production
CP
+
ADP
ATP
+
C
Phosphocreatine: an ATP “buffer”
Diet or
Glycine+
Arginine+
Ornithime
creatine
Creatine
Kinase
Phosphocreatine
?
ATP
?
ADP
Oxid active
Metabolism
Energy Transfer
• Heat is the end product of almost all the energy released
in the body.
O2 Fuel
ADP+Pi
Respiration
ATP
Biosynthesis
Mechanical
work
CO2+H2O
Transport
work
How to maintain a stable body weight
• Energy Intake – Energy Output
• Energy output
• Performing essential metabolic functions of the body
• Performing various physical activities
• Digesting, absorbing, and processing food
• Maintaining body temperature
set point
• Body weight in adults is usually
regulated around a relatively constant
set point.
• Theoretically this can be achieved by
reflex adjusting caloric intake and/or
energy expenditure in response to
changes in body weight.
What is fat?
Your 'body mass index' or BMI is a
measure of body fat based on
height and weight.
A BMI of:
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under 20 = underweight
20-25 = normal
25-30 = overweight
30+ = obese
Weight
BMI=
2
(Height)
(Kg /m2)
For example:
A 70kg person with a height of 180cm
70
BMI=
=
21.6
2
(1.8)
(Kg /m2)
OBESITY
• Energy intake > energy expenditure
• Abnormal feeding regulation
• Psychogenic factors
• During or after stressful situations
• Neurogenic abnormalities
• Hypothalamus
• Genetic factors
• Childhood overnutrition
BASIC CONCEPTS OF ENERGY
EXPENDITURE
Metabolic Rate
• Total energy expenditure per unit time
is called the metabolic rate.
• Normally expressed in terms of the rate
of heat liberation during the chemical
reactions
• calories
o
1C
Energy
1 liter
Kilocalorie is
the amount of
heat required
to raise the
temperature of
one liter of
water one
degree Celsius.
ΔE = H + W
ΔE
internal energy liberated during
breakdown of an organic molecule
H
heat
W
Energy used to perform work
energy released
For WORK
40%
60%
HEAT
The energy used for work must first
be incorporated into molecules of
____.
ATP.
Factors that affect the metabolic rate
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Age (↓with ↑age)
Sex (women less than men at any given size)
Height, weight, and body surface area Growth and growth hormone
Pregnancy, menstruation, lactation
Infection or other disease
Recent ingestion of food
Prolonged alteration in amount of food intake
Muscular activity during or just before measurement
Emotional stress
Environmental temperature
Body temperature
Sleep (↓during sleep)
Circulating levels of various hormones, especially epinephrine,
nonepinephrine , thyroid hormone, sex hormone, and leptin
Measurement of Energy Metabolism
water
Direct
Calorimetry
Accurate
Thermometer
Measurement of Energy Metabolism
• Indirect calorimetry
• Thermal equivalent of the food : Kcal/g
• Physical thermal equivalent
• Biological thermal equivalent
• Protein: biological thermal equivalent
< physical thermal equivalent
Indirect calorimetry
• Thermal equivalent of oxygen
• Heat production by consuming one liter of
oxygen to oxidize a specific type of food
with glucose, 5.01 cal (kcal) are released;
1 liter of
with fat,
4.70cal;
oxygen is
metabolized with protein, 4.60cal.
Averages about 4. 82cal.
Indirect calorimetry
• RESPRIATORY QUOTIENT (RQ)
• The ratio of the volume of CO2 produced to
volume of O2 consumed when a type of
food is oxidized
The Caloric Values of Foods and The Relative Data
Food
Heat production (KJ/g) Consumption ProductionThermal Respiratory
of CO2
of O2
equivalent quotient
Physical Biological
(L/g)
(RQ)
(L/g)
(kJ/g)
calorie calorie
Glucose 17.16 17.16
0.83
0.83
20.94
1.00
Protein 23.44 18.00
0.95
0.76
18.83
0.80
Fat
2.03
1.43
19.67
0.71
39.77 39.77
Indirect calorimetry
• Energy metabolic rate
= energy equivalent of oxygen ×
oxygen consumption
Indirect calorimetry
• Methods of measuring CO2 production
and O2 consumption
• Open circuit method
• Closed circuit method
Indirect calorimetry
O2
mouthpiece
flap
Recording
on drum
Soda
lime
water
Counterbalancing weight
Factors that affect energy
metabolic rate
• Physical activities
Form of activity
Awake lying still
Sitting at rest
Cleaning the window
Washing clothes
Cleaning the floor
Playing volleyball
Playing basketball
Playing football
Heat output (Kj/m2/min)
2.616
3.399
8.301
9.887
11.369
17.045
24.216
24.969
Factors that affect energy
metabolic rate
• Psychic activity
Factors that affect energy
metabolic rate
• Thermogenic effect of food-specific
Dynamic Action of food
Factors that affect energy
metabolic rate
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Environmental temperature
20℃-30℃
Cold stress
Shivering thermogenesis
Non-shivering thermogenesis
Basal metabolism
• Basal metabolic rate (BMR)
• The minimum energy expenditure for
the body to exist
• 50-70% of the daily energy expenditure
• BMR is usually expressed as calories per
hour per square meter of body surface
area.
Factors that influence the BMR
• Thyroid hormone, male sex hormone,
growth hormone and fever BMR(up)
• Sleep and malnutrition BMR(down)
Body Temperature and
Temperature Regulation
Body Temperature
• Skin temperature
• Changing with the
temperature of the
surroundings
• Core temperature
• Maintaining constant
Normal core temperature
Site
Mean value of
temperature
Standard
deviation
Range of variation
of temperature
Axilla
36.79oC
0.357
36.0~37.4oC
Oral Cavity
37.19oC
0.249
36.7~37.7oC
Rectum
37.47oC
0.251
36.9~37.9oC
Physiological fluctuations of
the body temperature
• Circadian rhythm
• Diurnal rhythmic changes with a variation of
1oC
• Sex difference in body temperature
Physiological fluctuations of
the body temperature
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Age
Emotional stress
Muscle activity
Food, drugs
Temperature Regulation
• Body temperature is
controlled by
balancing heat
production against
heat loss
Temperature Regulation
• Heat production
• Major organs of heat production in the body
Percentage in
body weight
The Brain
The Internal
Organs(i.e. Liver
and Spleen, etc.)
The Muscle & Skin
The Others
Percentage in
at rest
Heat-production
during labor
2.5
34
16
56
1
8
56
7.5
18
10
90
1
Temperature regulation
• Modes of heat-production
• Shivering thermogenesis
• Non-shivering thermogenesis
• Control of thermogenesis
• Thyroxine, catecholamines, androgens and
GH
• Sympathetic nervous system
Temperature regulation
• Heat loss
• By the skin
• By expiration,
urination, and
defecation
• By panting
How heat is lost from the skin
surface?
• Radiation: 60%
• Infrared heat rays
How heat is lost from the skin
surface?
• Conduction
• Conduction to solid
objects
• Conduction to air
• Effect of clothing on
conductive heat loss
How heat is lost from the skin
surface?
• Convection
• Cooling effect of wind
How heat is lost from the skin
surface?
• Evaporation
• A necessary cooling mechanism at very
high air temperature
• 0.58 calorie of heat is lost for 1g water that
evaporates
How heat is lost from the skin
surface?
• Evaporation
• Insensible evaporation
• 450-600 ml H2O/day
• Evaporation of sweat
• Sweat gland
• Cholinergic sympathetic nerve innervation
Temperature regulation
• Control of heat loss
• By regulation of skin blood flow
• By regulation of sweat glandsm
Regulation of body
temperature
• The temperature of the body is
regulated almost entirely by nervous
feedback mechanisms.
• Behavioral control of body temperature
Regulation of body
temperature
• Temperature receptors
• Temperature receptors in the skin
• Warmth receptors
• Cold receptors:more
• Deep body temperature receptors
• Spinal cord, abdominal viscera, great veins
Thermoreceptors
• Peripheral Thermoreceptors
• Deep body temperature receptors
Regulation of body
temperature
• Anterior hypothalamic-preoptic
area(AH/PO)
• Cold-sensitive neurons
• Heat-sensitive neurons
• Serve as thermostatic body temperature
control center
Regulation of body
temperature
• Temperature-regulating centers
• In the hypothalamus
• Preoptic and anterior hypothalamic
(PO/AH) region
Regulation of body
temperature
• Set point
• A critical body
temperature
value: 37.1oC
• PO/AH
Neuronal effector mechanisms that
decrease or increase body
temperature
• Temperature-decreasing mechanisms
when the body is too hot
• Vasodilatation
• Sweating
• Decrease in heat production
Neuronal effector mechanisms that
decrease or increase body
temperature
• Temperature-increasing mechanisms
when the body is too cold
• Skin vasoconstriction
• Increase in heat production
• Shivering(primary motor center for shivering in
hypothalumus)
• Sympathetic excitation
• Thyroxine(eskimos-higher incidence of toxic
thyroid goiters)
Concept of “set point”
• It is clear that at a critical body core
temperature, at a level of almost exactly
37.0oC , drastic changes occur in the rates of
both heat loss and heat productlon.
• At temperatures above this level, the rate of
heat loss is greater than that of heat
production ,so that the body temperature
falls and reapproaches the 37.0OC level.
summary
• Terms
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Respiratory quotient
Specific dynamic action of food
Basal metabolic rate
Body temperature
Set-point
• List the factors that affect energy metabolic
rate
• Describe the modes of heat-loss from the skin
General question
• How dose the body actively maintain a
constant body temperature despite
changes in ambient temperature?