energy balance and temperature regulation energy balance temperature regulation

Energy Balance and Temperature Regulation

Energy Balance

Temperature Regulation

Definition of energy metabolism

Energy metabolism liberation storage transformation utilization

Energy balance

energy input =energy output

Energy Balance

The difference between the number of kilocalories that you eat and the number of kilocalories that you burn

obesity

Food energy

Metabolic pool in body

External work

Internal work

Thermal energy

(heat)

Energy storage

Energy input Energy output

First law of thermodynamics:

Energy cannot be created or destroyed, but it can be converted from one form to another

Source and utilization of energy

Foods (carbohydrate,fat and protein)

H2O,CO2

O2

oxid

atio

n

ATP

ADP

Pi

C

C-P

Heat

(>50%)

Energy

<50%

Muscle contraction

Nerve conduction

Active transport

Digestion

Secretion

Anabolism

release transport storage utilization

ATP

ATP is a combination of adenine,ribose,and three phosphate radicals.

ATP(adenosine triphosphate)

ATP:An energy “currency” ATP is generated by combustion of

carbohydrate, fat and protein . ATP can be utilized by cell directly (high

energy phosphate bonds) Synthesis and growth Muscular contraction Nerve conduction Active transport Gland secretion

Phosphocreatine

Phosphocreatine: Another energy-rich phosphate compounds found in the muscle and brain acts as an accessory depot for energy of

ATP and for buffering the concentration of ATP

This reversible interrelation between ATP and phosphocreatine is demonstrated by the following equation: Phosphocreatine+ADP=ATP+Creatine

Energy expenditure

energy input (food)

Carbohydrate (mainly glucose ) 65% of the total energy (4.1kcal/g )

Glycolysis Citric acid cycle

Glucose: a major energy source

Oxidation6

energy input (food)

Fat – fat acid (9.5kcal/g) The storage fat in the body is

much greater than that of glucose

The energy released by oxidation of fat is 2 times that produced by the same amount of glucose

energy input (food)

Protein: (synthesize body structure protein) 4.3kcal/g

The amount of energy provided by protein is relatively small in human being

In special situation , the protein is the main source of energy . (Hungry for a long time)

Factors control food intake

The feeding center tell us to eat, whereas the satiety center tell us when we have had enough.

comparison of a normal rat with a rat whose satiety center has been destroyed.


The size of fat stores Leptin:excellent indicator of total amount of TG

store Leptin↑+ receptor →appetite↓and metabolic rate↑ Recepter:in the ventromedial hypothalamus(satiety

center) Suppression of appetite Responsible for the long-term matching of food intake

to energy expenditure


The extent of glucose utilization and insulin secretion insulin→signals satiety The extent of glucose utilization appears to be

more important in determining the timing of meals

Low blood glucose levels activate lateral hypothalamic neurons in the vicinity of appetite centers


Psychosocial and environmental influences Stress, anxiety, depression and boredom

→unrelated to energy needs Food supplies are abundant

Energy 0utput

Internal work Na ＋ - K ＋ pump muscle contraction (shivering) or maintain

the posture External work:

go upstairs (potential energy ↑ ) lift the object from low site to high one

Energy 0utput

Form of energy output Heat (During biochemical processing)

75% of the energy is lost as heat (directly) 25% of the energy is available to accomplish

work (internal work or external work) (indirectly)

50%heat

Energy in

Nutrient molecule

s

50% ATP

25% lost as heat during

expenditure

25% energy accomplish work

75% energy will be lost as

heat

Obesity

20%overweight greater than normal body mass index(BMI)=height2/weight BMI≥24: overweight BMI≥28: obesity

Obesity

20%overweight greater than normal Energy intake ＞ energy expenditure

Abnormal feeding regulation Psychogenic factor

During or after stressful situation Neurogenic abnomality

Hypothalamas Disturbances of the satiety-appetite control

Genetic factor Childhood overnutrition

Three possible states of energy balance

Neutral energy balance : Energy input =energy expended

Positive energy balance : Energy input > energy expended, store in adipose

tissue , body weight increase– obesity Negative energy balance :

Energy input < energy expended, lose weight

Energy Metabolism

Terminology

metabolic rate = energy expenditure/unit of time (kcal/hr)

Heat is the end product of almost all the energy release in the body

Calorie : the basic unit of heat energy

--the amount of heat required to raise the temperature of 1g of H2O 1℃

Method of metabolic rate determination

Direct calorimetry

If person doesn’t do external work, energy output = heat released, we calculate the heat liberated from the body in a given time by a special calorimeter. so we can determinate the metabolic rate.

Measurement of metabolism rate Direct calorimetry

thermometer

thermometer

water

water

Thick insulation

Measurement of metabolism rate

Indirect calorimetry Principle:

food + O2→CO2+H2O+energy(heat) C6H12O6+6O2 → 6CO2+6H2O + H (law of definite

proportions )

Measurement of metabolism rate Indirect calorimetry

Energy (Thermal) equivalent of food Heat production (The amount of energy liberated ) by

oxidation or combustion of 1g of such food physical caloric value and biological caloric value

Energy equivalent of oxygen Heat production (The amount of energy liberated ) by

consuming of one liter of oxygen to oxidize a specific type of food

glucose: 5.01 kcal, fat: 4.7 kcal, protein: 4.6 kcal

typical mixed diet is 4.8 Kcal

Indirect calorimetry

An average estimate of the quantity of heat produced per liter of O2 consumed on a typical mixed diet (Energy equivalent of

oxygen )

15 liter/hr =O2 consumption

×4.8 Kcal/liter =energy equivalent of O2

72 Kcal/hr =estimated metabolic rate

?

metabolic rate = energy expenditure/unit of time

Indirect calorimetry

Method of measuring O2 consumption Closed circuit method

C6H12O6+6O2 6CO2+6H2O + H

Heat = thermal equivalent of oxygen ×the amount of O2 consumed

Metabolic rate = Thermal equivalent of oxygen (4.825kcal/L)×oxygen utilized(L).

law of definite proportions

Mouth piece

Soda lime

waterRecording drum

Counterbalancing weight

volume

time

Factors affect the energy metabolic rate

Physical activity

Psychic activity


Thermogenic effect of food Specific dynamic action of food

the metabolic rate of a person increases after a meal. Protein increase it significantly.



Environment temperature: >30℃ or <20 ℃ metabolic rate↑

Rate of energy expenditure for a 70kg person during different types of activity

Form of activity energy expenditure (Kcal/h)

Sleeping 65Sitting at rest 100Typewriting 140Walking slowly on level 200Bicycling on level 304Swimming 500 Jogging 570 Rowing 828 Walking up stairs 1100

Basal metabolic rate (BMR)

BMR

The minimum energy expenditure for the body to existence

BMR is not the lowest metabolic rate, metabolic rate will reduce further in deep sleep

Basal metabolic rate (BMR)

minimal waking rate of internal energy expenditure under basal condition

basal condition physical rest: muscle and nerve relaxation room temperature: 20-25 ℃ Fasting: Not have any eaten food 12 hours

before determination waking?

Why should subject keep awake?

Method for determining BMR

Under the following condition At physical rest At mental rest At a comfortable room temperature Avoiding Specific dynamic action of food

The meaning of determining the BMR For a healthy person, the BMR does not

vary more than 10 to 15 percentage from the normal values. Hyperthyroid: increase 25%~80% Hypothyroid: decease 20%~25%

Other factors affected the BMR

Gender and age

Other factors affected the BMR

Hormone Thyroid hormone : BMR↑ Male sex hormone

Sleep and malnutrition Deep sleep : BMR↓ ↓

BMR is not the lowest metabolic rate, metabolic rate will reduce further in deep sleep

how to compare MR of different person?

Because sex age height and weight affect the basal rate of energy expenditure.

the output in kilocalories per hour per square meter of surface area is normally about the same.

The BMR is usually expressed as calories per hour per square meter of body surface area

Data used to measure energy Thermal( Energy) equivalent of food

The amount of energy liberated by oxidation or combustion of 1g of such food

thermal ( Energy) equivalent of oxygen Heat production by consuming of one liter

of oxygen to oxidize a specific type of food the amount of the food oxidation the amount of the O2 consumption

Temperature regulation

Why keep the temperature constantly ？

Even moderate elevations of body temperature begin to cause nerve malfunction and irreversible protein denaturation.

Higher than 44 to 45℃, maintained for certain length of time is also fatal.

An optimum environment for the cells, it is necessary to maintain a constant body temperature.

Body temperature

Skin temperature : variation by surrounding temperature

Core temperature: maintaining constant

Normal core temperature

No single temperature level can be considered to be normal, it is a range

Influence factors of core temperature

Physiological fluctuation of the body temperature

Circadian rhythm Diurnal rhythmical changes with a variation of 1℃


biological clock

Sex different in body temperate Female : check safe period

0.5 ℃higher during the half of the cycle from the time of ovulation to menstruation


: the older , the lower


Emotional stress: Food :specific dynamic action of food Drugs: tranquilizer



Heat gain must balance heat loss to maintain a stable temperature


Heat production Major organs of heat production in the body


Modes of heat production Shivering thermo-genesis:

rhythmic oscillation skeletal muscle contractions Non - shivering thermo-genesis

brown fat : a special fat tissue in newborn Mediated by hormone: Thyroid hormone and

epinephrine Important for newborns (lack the ability to shiver)


Heat loss (down temperature gradient) By skin By expiration, urination

and defecation By panting

Temperature regulation How heat is lost from the skin surface? (down a

thermal gradient) Radiation (60%) :by Infrared heat rays

emission or absorption depend on the difference in temperature between the surface of skin and other object in the environment

camouflage clothes


How heat is lost from the skin surface? Conduction : in direct contact with each other

Conduction to solid subjects Conduction to air Effect of clothing on

conductive heat loss


How heat is lost from the skin surface? Convection (air or water current)

Cooling effect of wind

Conduction and convection Similarity:

direct heat transfer to the material which contacts with the body

Dissimilarity conduction :Heat transfer to and from solids Convection: heat is transferred from the skin by

conduction to the air heated air moves away from the skin, more heat is lost to

the unheated air that is continually brought in contact with the skin


How heat is lost from the skin surface? When T Environmental ＞ T skin ,evaporation is the only

avenue for heat loss body is gaining heat by radiation and conduction 0.58 Calorie of heat is lost

for 1g water that evaporates

Temperature regulation How heat is lost from the skin surface?

Evaporation (T Environmental ＞ T skin ) Insensible evaporation : airways and surface of skin

(without controlled , passive) 450ml – 600ml H2O/day (fluid infusion)

Sensible evaporation: sweat (hot , humid days) Sweat gland: sympathetic

cholinergic nerve innervations Evaporating and dripping

of sweat

Regulation of body temperature

temperature-regulating centers: hypothalamus Afferent input

Peripheral thermoreceptors: Skin

cold and warmth receptor more cold receptors than warmth receptors

Central thermoreceptors : hypothalamus itself

Temperature regulation (Control of heat loss) Posterior region of hypothalamus

activated by cold triggers reflexes :mediate heat production and heat

conservation. skin vasoconstriction Increase in heat production

Anterior region of hypothalamus, activated by warmth initiates reflexes :mediate heat loss

Vasodilation sweating Decrease in heat production


Nervous feedback mechanism (short term) Humeral regulation : thyroid gland

hormone( long term ) Behavioral control : shivering


Hypothalamus : sensitive thermostat The concept of set point: thermostat

Any deviation from a very critical body core temperature, between the level of 37.0 and 37.1 , would cause drastic change in both the ℃rate of heat loss and heat production, then bring the body temperature back to set point

T skin T core

Peripheral thermo receptors (skin)

Central thermo receptors (in hypothalamus)

Hypothalamus thermoregulatory center

Behavioral adaptations

Motor neurons Sympathetic nervous system

Control of heat production or

loss

Muscle tone Skin vaso -constriction and

vasodilation

sweating

Major thermoregulatory pathway

Abnormality temperature regulation

Fever : the point is reset at an elevated temperature. endogenous pyrogen: raise the “set-point” .(PG↑)

(Aspirin )

Hyperthermia : no related to infection

--malfunction of the hypothalamic control centers

Hyperthermia in sustained exercise:

heat loss mechanism reflexly increased


Heat stroke Breakdown of the hypothalamic thermoregulatory

systems Prolonged exposure to a hot humid environment


Frostbite Excessive cooling of

a particular part of the

body , the tissue in that

area is damaged

Summary

Definition 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

Question

How does the body actively maintain a constant body temperature despite changes in ambient temperature?

energy balance and temperature regulation energy balance temperature regulation

Documents

energy of atp

total energy

energy outputenergy

energy currencyatp

potential energy

glucosethe energy

energy needsfood supplies

utputform of energy