Body Temperature

Huang QinHuang Qin（（ Tel 2995285Tel 2995285 ））

Major TopicsMajor Topics

FirstFirst Normal Body TempNormal Body Temperatureerature

SecondSecond HeatHeat BalanceBalance

ThermogenesisThermogenesis

ThermolysisThermolysis

Third Third ThermoregulationThermoregulation

Thermo reflex Thermo reflex

SetSet Point Theory Point Theory

TempTemp Regulation Example Regulation Example

Normal Body Temp.

core temp. is the temp. in deep core temp. is the temp. in deep tissues of the body. tissues of the body.

FFluctuates very little in normalluctuates very little in normal shell temp. is shell temp. is the surface Temp. the surface Temp.

of the body. of the body.

Fluctuates widely in normalFluctuates widely in normal

20 ~40℃ ℃20 ~40℃ ℃

1. Body core temp. & surface temp.

skin subcutaneous tissue fat

寒冷环境 炎热环境

体热模式

Body Temp.Body Temp.

refers to the average refers to the average core temp. core temp.

T ＜ 22℃→ 心跳停止T ＞ 43℃→ 酶变性死T = 27℃→ 低温麻醉

Temp. unit :Temp. unit : Usually measured in degrees Usually measured in degrees

Centigrate Centigrate

((C).C). degrees Fahrenheit (degrees Fahrenheit (F).F).

环境温度 体热温度

Normal Body Temp.

In normal, the body temp. remains In normal, the body temp. remains almost exactly constant (±1.0℃)almost exactly constant (±1.0℃)

Environment temp. Environment temp.

riserise

fallfall

endotherm (warm-blood Animal)endotherm (warm-blood Animal)

Body temp.

constant

Normal range of body temp.Normal range of body temp.

axillary temp.axillary temp. 36.0-37.4 ℃36.0-37.4 ℃ oral temp.oral temp. 36.7-37.7 ℃36.7-37.7 ℃ rectal temp.rectal temp. 36.9-37.9 ℃36.9-37.9 ℃

EsophagusEsophagus

Tympanic membraneTympanic membrane

Temp. measuring equipmentTemp. measuring equipment

Mercurial thermometerMercurial thermometer

Recording thermometerRecording thermometer

3. 3. Body temp varies Body temp varies physiologicallyphysiologically

1. circadian rhythm1. circadian rhythm: 2~6 AM, lowest: 2~6 AM, lowest

1~6 PM, highest 1~6 PM, highest

(±1℃)(±1℃)

2. Sex difference2. Sex difference: the female average body : the female average body temp. is higher than the male’s temp. is higher than the male’s ( 0.3℃)( 0.3℃)

3. Age difference3. Age difference: newborn baby: newborn baby

old person old person (slightly)(slightly)

4. Emotion4. Emotion , , physical workphysical work, , menses :menses :

(> 2℃)(> 2℃)

Heat balance:Heat balance: thermogenesisthermogenesis and thermolysisand thermolysis

Heat is continuously being produced in Heat is continuously being produced in the body as a by-product of metabolism the body as a by-product of metabolism

thermogenesisthermogenesis Heat is continuously being lost to the Heat is continuously being lost to the

surroundings surroundings thermolysisthermolysis Body temp. is closely related to the Body temp. is closely related to the

balance between thermogenesis and balance between thermogenesis and thermolysis:thermolysis:

rate of heat production = the rate of lossrate of heat production = the rate of loss

(the person is in heat balance, body temp. is (the person is in heat balance, body temp. is stable.)stable.)

ReverselyReversely ：： the body temp. is the body temp. is increasing/decreasingincreasing/decreasing..

图 8-2 体热平衡模式

热输出辐射传导对流蒸发

热来源代谢环境

1. Thermogenesis1. Thermogenesis

Organs of thermogenesisOrgans of thermogenesis

In restIn rest : viscera (liver) and brain : viscera (liver) and brain

56% 16%56% 16%

In sportIn sport : skeletal muscle : skeletal muscle

90%90%

Means of thermogenesisMeans of thermogenesis 1) Basal metabolism (clear-headed,quiet)1) Basal metabolism (clear-headed,quiet)

2) Shivering(chill)2) Shivering(chill) flexor and extensor contractflexor and extensor contract

3) Non-shivering thermogenesis3) Non-shivering thermogenesis neural and hormonalneural and hormonal ：： sympathetic sympathetic

nervous nervous norepinephrinenorepinephrine brown fat catabolismbrown fat catabolism

4) Specific dynamic effect4) Specific dynamic effect

2. Thermolysis2. Thermolysis

Organs of thermolysisOrgans of thermolysis

1) skin : major organ 1) skin : major organ 85%85%

2) respiratory tract2) respiratory tract

digestive tract digestive tract

urinary tracturinary tract

2. Heat transfers 2. Heat transfers ：： from body core to skinfrom body core to skin

Heat conducts directly from body Heat conducts directly from body core to skin. core to skin.

efficiency: Fat < skeletal muscleefficiency: Fat < skeletal muscle

Heat transfers along with blood flow Heat transfers along with blood flow to the skin.to the skin.

Skin structureSkin structure

E. epidermis E. epidermis

F. dermis F. dermis

G. subcutaneous G. subcutaneous tissue tissue

J. sweat glandJ. sweat gland

I. Arterial and I. Arterial and venous vessel.venous vessel.

Features of skin vesselFeatures of skin vessel

Arteria, capillary and vein. Arteria, capillary and vein. many connections between arteria many connections between arteria

and vein : A-V connecting vessel.and vein : A-V connecting vessel. The vessel is controlled by The vessel is controlled by

sympathetic nerve, and the sympathetic nerve, and the postganglionic fiber is cholinergic postganglionic fiber is cholinergic (not adrenergic):(not adrenergic):

Ach (Acetylcholine) as transmitterAch (Acetylcholine) as transmitter

Effect of sympathetic nerve on Effect of sympathetic nerve on

skin blood flowskin blood flow

Sympathetic nerve excitesSympathetic nerve excites

the end release Ach (Acetylcholine)the end release Ach (Acetylcholine)

Ach is vasodilatingAch is vasodilating

skin blood vessel dilateskin blood vessel dilate

skin blood flow skin blood flow

Heat exchanges Heat exchanges

Not Noradrenalin

3. Means of Thermolysis3. Means of Thermolysis

Evaporation

Radiation

Convection

Conduction

nude person at room temperaturenude person at room temperature

1.1. RadiationRadiation: heat transfers between : heat transfers between two bodies that are two bodies that are notnot in direct in direct contact. contact.

Main form is infrared rays. Main form is infrared rays.

body temp. body temp. RadiationRadiation

((60% of total heat lost) 60% of total heat lost)

person roomperson room

2. Conduction:2. Conduction: transfer of heat between transfer of heat between 2 bodies in direct contact (solid, liquid 2 bodies in direct contact (solid, liquid or gas). Heat flows down thermal or gas). Heat flows down thermal gradient.gradient.

conduction to objects:conduction to objects:

person 3% chairperson 3% chair

person 15% airperson 15% air

3. Convection3. Convection: heat transfer by : heat transfer by movement of fluid (liquid or gas). movement of fluid (liquid or gas). Depends on the speed of mass Depends on the speed of mass movement. movement.

air/water : temp. air/water : temp.

movement movement

way principle affected factor exampleway principle affected factor example

radiation infrared radiation infrared difference in temp. dressingdifference in temp. dressing

rays area of bodyrays area of body

conduction direct difference in temp.conduction direct difference in temp. IceIce

transfer ability to conduct heat refrigeratetransfer ability to conduct heat refrigerate

convection direct difference in temp. fanconvection direct difference in temp. fan

transfer velocity of airtransfer velocity of air

Compare : radition, conduction and Compare : radition, conduction and evaporationevaporation

4. Evaporation:4. Evaporation: evaporation of water requires evaporation of water requires

a lot of heat. a lot of heat.

Insensible perspirationInsensible perspiration

water evaporates insensibly: skin and lung water evaporates insensibly: skin and lung

600ml/d600ml/d Sensible perspiration (Sweating)Sensible perspiration (Sweating)

when bodies becomes overheated, large when bodies becomes overheated, large amount of sweat are secreted onto the amount of sweat are secreted onto the surface of skin by the sweat gland : surface of skin by the sweat gland : evaporative cooling of the body. evaporative cooling of the body.

temp. of surroundings temp. of surroundings

velocity of air movementvelocity of air movement

humidity of air humidity of air

influencing factors

Sweat Sweat glandgland

1) A deep coiled portion that secretes the sweat.

Sodium, chlorideSodium, chloride

2) A duct portion passing outward through the dermis, by which sweat flow onto the skin surface.

**osmotic pressure of end-sweat is lower than plasma**osmotic pressure of end-sweat is lower than plasma

Sweating reflexSweating reflex

afferent nerveafferent nerve center of sweating center of sweating

(hypothalamus)(hypothalamus) efferent nerveefferent nerve

Conclusion of thermolysisConclusion of thermolysis

Radiation, conduction and Radiation, conduction and convectionconvection is the major way of is the major way of thermolysis When body temp. is thermolysis When body temp. is Higher than surroundingsHigher than surroundings

Evaporation Evaporation is the only way of is the only way of thermolysis when body temp. is thermolysis when body temp. is lower than surroundings.lower than surroundings.

ThermoregulationThermoregulation

The body temp. keep constant is The body temp. keep constant is important for life.important for life.

Autonomic thermoregulationAutonomic thermoregulation

nervous regulation: nervous regulation: receptorreceptor, afferent , afferent nerve, nerve, centercenter, efferent nerve, , efferent nerve, effectoreffector

Behavioral thermoregulationBehavioral thermoregulation: dressing , : dressing , fan fan

Temp. ReceptorTemp. Receptor

1. Peripheral Thermal Receptor1. Peripheral Thermal Receptor Warmth Receptor Cold ReceptorWarmth Receptor Cold Receptor

2. 2. centralcentral thermal receptors thermal receptors classified into warmth-sensitive neuronclassified into warmth-sensitive neuron cold-sensitive neuroncold-sensitive neuron spinal cord, hypothalamusspinal cord, hypothalamus

Cold >> Warmth, more concerned with Cold >> Warmth, more concerned with hypothermiahypothermia

10 : 110 : 1

Thermoregulation CentreThermoregulation Centre

HypothalamusHypothalamus : : the central integrator of thermoregulationthe central integrator of thermoregulation, ,

called “thermostat”called “thermostat”

Preoptic anterior hypothalamusPreoptic anterior hypothalamus (PO/AH)(PO/AH)

视前区视前区 -- 下丘脑前部下丘脑前部

warmth-sensitive / cold-sensitive neuronswarmth-sensitive / cold-sensitive neurons****receives input from peripheral and deep receives input from peripheral and deep tissue thermal receptors when body temp. tissue thermal receptors when body temp. is is low low / / highhigh..

Temp. EffectorTemp. Effector

1. blood vessels1. blood vessels

2. sweat glands2. sweat glands

3. skeletal muscle3. skeletal muscle

Set Point theorySet Point theory Normal homeostasis operates to keep the body Normal homeostasis operates to keep the body

temperature within a very narrow temperature within a very narrow rangerange ，， called the set point. This set point acts called the set point. This set point acts as a "trigger" for the body to respond in a as a "trigger" for the body to respond in a manner, which activates physiologic processes manner, which activates physiologic processes that influence temperature elevation or that influence temperature elevation or decrease .decrease .

Similar to Air conditionerSimilar to Air conditioner40

37

36

Set Point

Body Temp. 37

Normal

Body Temp. 40

“Normal”

Mechanism of increased heat Mechanism of increased heat loss when the body becomesloss when the body becomes overheatedoverheated

1. Skin vessel dilated.

2. Sweating

3. Heat production reduce

Mechanism of heat Mechanism of heat conserving when the body conserving when the body becomes becomes cooledcooled

1. Skin vessel constricted.

2. Increasing of heat production

shivering, sympathetic excitation and thyroxin releasing.

3. other :

Piloerection

Behavioral control of body temp.Behavioral control of body temp. thermostatic control thermostatic control human being——human being——behavioral controlbehavioral control

body temp. high/low body temp. high/low

feeling overheated /cooled and feeling overheated /cooled and discomforted discomforted

Less/more clothing, etc.Less/more clothing, etc.

Set Point changeSet Point change FeverFever

Pyrogens act on the anterior hypothalamus Pyrogens act on the anterior hypothalamus to to raise the set pointraise the set point to a higher level. to a higher level.

Pyrogen : Pyrogen : some proteinsome protein increase set increase set point point

Body Temp. 37

40

37

36

Set Point

SummarySummary

Normal body temp range.Normal body temp range. Ways of thermolysis.Ways of thermolysis. Center, receptor and effector of Center, receptor and effector of

thermoregulation.thermoregulation. Mechanism of body regulating the Mechanism of body regulating the

temp. to normal when the body temp. to normal when the body temp. is higher or lower than set temp. is higher or lower than set point.point.