Chapter 10

Body Temperature, Heat, Fat, and Body Temperature, Heat, Fat, and MovementMovement

Figure 10.1 The human temperature regulation system can increase or decrease body temperature.

Anteriorhypothalamus

set-point

Control center

Posteriorhypothalmus

Actuators

SweatingSkin vasodilation

Decrease metabolism

Muscle shiveringSkin vasoconstrictionIncrease metabolism

Skin thermalreceptors

Hypothalamic thermalreceptors

Coretemperature

Skintemperature

–

+

Figure 10.2 Examples of resistance–temperature curve for three NTC thermistors, = 3000 , 3500 K, and 4000 K. R0 is the resistance at T0 = 298 K.

00 T

11exp

TTRR

V oltm ete r

C onstan tan

C opperC opper

C o ld junction , T 2

(R e fe rence)

T 1 , H o t junction(M easuring p robe)

Figure 10.3 The J type thermocouple is formed from copper and constantan.

C1 and C2 are constants that depend on the thermocouple pair with T in kelvins

Probe (thermistors)

Wheatstone bridge

Signal conditioner and final temperature

detector ( processor)

Digital display

Audible alarm

Figure 10.4 An electronic thermometer uses a thermistor sensor probe.

Ear

IR

Shutter Ambient sensor

Sensor Amp.

MUX A/D

Shutter switch

Window Waveguide

Micro processor

Digital display

T a

T b

Figure 10.5 The infrared thermometer opens a shutter to expose the sensor to radiation from the ear.

A = effective body (target) area = Stefan-Boltzmann constanta = emissivity of surroundings (sensor)Tb = body temperatureTa = sensor temperature

Net flux of infrared radiation:

Constantan

Copper

Insulation layer

Thermocouple connection

Metal wall Cooling tubes

Figure 10.6 In a gradient layer calorimeter, thermocouples measure the difference in temperature across the wall. Ventilating system and measurements not shown.

air mass flow rate

Air in

Air out

T1

T2

Insulated chamber(polyurethane)

Thermometer

Thermometer

Figure 10.7 An air–flow calorimeter measures inlet and outlet temperatures, flows, and humidity.

heat loss

specific heattemperature change of the ventilating air

T1

T2

Water in

Water out

Inlet thermometer

Outlet thermometerPolyvinyl chloride tubes

Figure 10.8 The water flow calorimeter measures the inlet and outlet water temperature.

AC

Powersource

Powermeter

Thermostat

Heater

Feedback control

Figure 10.9 The compensating heater calorimeter requires less heater power when the subject supplies heat.

From

Inspired gas source

Patient Expired gas from patient

Switch

CO 2

Pressure transducer

Vacuum pump

Flow transducer

Thermistor

Exhaust

Computer control

Mixing chamber

O 2

Figure 10.10 A microcomputer-based open-circuit system includes a mixing chamber, O2 and CO2 analyzers, and the various variables (pressure, flow, temperature) used to calculate .

H um id ifie r

C O 2 and O2ana lyzers

F rom insp ired gas source

E xha la tionva lve

E xp ira to ry lim b

Insp ira to rylim b

R oom a ir

C onstan tflow

genera to r

F IO 2

FE C O 2 ,FE O 2 F *C O 2

M echan ica lven tila to r

M etabo licm on ito r

P a tien t

Figure 10.11 A dilution system used by Deltatrac uses mechanical ventilation. FIO2 is the inspired oxygen concentration, FECO2 is the true expired carbon dioxide concentration, FEO2 is the expired oxygen concentration, and F*CO2 is the diluted carbon dioxide concentration.

C O2 ana lyzer

F rom ventila tor

B ellow s

C O 2S crubber

M ix ingcham ber

S am plegas

A s oxygensupply and

analyzer

P atient

S pirom eter

Figure 10.12 A closed-circuit system uses the volumetric loss principle. The spirometer is used as an oxygen supply and the volume change as a function of time in the spirometer is used to calculate the rate of oxygen consumption.

2H2O deuterium waterH2

18O oxygen-18 enriched water

2H labeled water pool

18O labeled water and bicarbonate pools

2H disappearance (k2) = rH2O

18O disappearance (k18) = rH2O + rCO2

k18 – k2 = rCO2

Figure 10.13 Principle of the doubly labeled water method. r is the production rate, W is the size of total body water, k represents rate constants determined from the experiment.

(a)

Shoulder

Triceps

skinfold

Lange

caliper

(b)

Figure 10.14 (a) Lange skinfold caliper used for assessing thickness of subcutaneous fat. (b) Illustration of an example of skinfold measurement, triceps skinfold taken on the midline posterior surface of the arm over the triceps muscle.

Excitation ac current source (I)

Detected voltage drop (E)

Figure 10.15 In resistance measurement on the ipsilateral side of the body current flows through one arm, the trunk, and one leg.

V out = k

V i

(a)

Plastic ribbons

Connecting rods Parallelogram

linkage

Triaxial goniometer

(b)

Knee joint

Figure 10.16 (a) A goniometer attached to the shank and thigh to measure knee rotation. Vi is the input voltage. Vout is the output voltage that is proportional to the angle of knee rotation. (b) Subject wearing a triaxial goniometer on knee joint.

Seismic

mass

Cantilever

Strain

V a

E

Figure 10.17 Vertical acceleration of the accelerometer frame bends the cantilever beam because the seismic mass remains at rest. Voltage output (V) is proportional to the acceleration (a). E is the supply voltage.

Figure 10.18 An example of a gait analysis setup includes a four-camera kinematic system, two force platforms, and an electromyogram (EMG) telemetry system.

A/D converter

EMG receiver

Camera control

and Interface

Display system

Walk way

Analog interface

Camera 1

Camera 2 Camera 3

Camera 4

EMG transmitter

(option)

Force platforms (option)

Markers

Computer