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BIOELECTROBIOELECTRO--
MAGNETISMMAGNETISMJaakko Malmivuo
Demonstration slides
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AmberAmber
= amber
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Hans ChristianHans Christian rstedrsted 18191819
Magneticneedle
I
I
Battery
B
B
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600
Generation of bioelectric signalGeneration of bioelectric signal
Vm [mV]
200 400 800 1000
-100
-50
0
50
Time [ms]
K+
Na+
K+
K+
K+
K+
K+
K+
K+
K+K+
K+
K+
K+
K+
K+ K+
K+K+
K+
K+
K+
K+
Na+
Na+Na+
Na+
Na+Na+
Na+
Na+
Na+
Na+
Na+
Na+
Na+Na+
Na+
Na+
Na+
Na+
Na+
Na+Na+
Na+K+
K+
K+
K+
K+
Na+
Na+
Na+
Na+
Na+
Na+
Na+
Na+
Na+
Na+
Na+
Na+
Na+
Na+
Na+
Na+
K+
K+K+
K+K+
K+
K+
K+
K+K
+
K+
K+
K+
K+K+
K+K+
K+
K+
K+K+
K+K+
K+ K+Na+
Na+
Na+
Na+Na+
Na+Na+ Na+
Na+
Na+Na+
K+
Na+ K+
K+
Restoring ionic balanceRestoring ionic balanceDepolarizationDepolarization RepolarizationRepolarization
Na+
Na+
Na+
K+
K+
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Hubert MannHubert Mann
LEAD 3
LEAD 3
LEAD
2
LE
A
D
1
LE
A
D
1
RR LL
FF
4
6
53
2
18
10
9
7
Monocardiogram
1916
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Space clampSpace clamp
Is t = t1
x
Experimental chamber
Physiological salt solutionMembraneAxoplasm
Internal electrode
im
t = t4
t = t2
t = t3
Vm is constant along the axon
Vm
A B
i
o
Vm rm
Em
cm
im
imcimi
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mV
sec
Impulses in
sensory axon
Reflex ArchReflex Arch
Muscle
spindle
cm
sec
Muscle
stretch
Stretch
Muscle
Spinal
cord
mV
sec
Receptor potential
in sensory terminal
mV
sec
Synaptic potentials
in motoneuron
mV
sec
Impulses in
muscle fibers
mV
sec
Impulses in
motoneuron
gm
sec
Tension
in muscle
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TYPE OF DOUBLE LAYER SOURCESTYPE OF DOUBLE LAYER SOURCESEQUIVALENTEQUIVALENT
SOURCESSOURCES
Double layerDouble layersourcesource
EquivalentEquivalentdouble layerdouble layersourcesource
EquivalentEquivalent
dipoledipole
ClosedCloseddouble layerdouble layer
(Zero field)(Zero field)
(Null)(Null)
OpenOpendouble layerdouble layer
Various doubleVarious doublelayers withlayers with
the same openingthe same opening
Open doubleOpen doublelayer with twolayer with two
openingsopenings
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0 5 10 15 25 30 35 40 45 50 55 60 6520 ms
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Heart rate 1/2Heart rate 1/2NORMAL SINUS RHYTHMImpulses originate at S-A node at normal rate
All complexes normal, evenly spaced. Rate 60 100/min.
S-A node
SINUS BRADYCARDIAImpulses originate at S-A node at slow rate
All complexes normal, evenly spaced. Rate < 60/min.
1.0 s
1 mV
2
M ti fl d it [T]
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MOG
Biomagneticsignals
MEGMEG
MCG
MMG
BiomagneticBiomagnetic
signals andsignals andmagneticmagneticnoisenoise
Frequency [Hz]
Static field of earth
10-11
10-10
(pT) 10-12
(nT) 10-9
10-13
10-14
(fT) 10-15
10-16
10-8
10-7
10-4
10-3 10-2 10-1 100 101 102 103 104 105 106
Thermal noise fieldin eddy-current shield
Thermal noise field of bodyThermalnoise fields
Laboratorynoise
Line frequencyand harmonicnoise
Radio-
frequencynoise
high
low
Magnetic noise of brain
Geo-magneticnoise
Noise fields
Magnetic flux density [T]
Equivalentinput noise
Commercialflux-gate
magnetometer
NASAflux-gatemagnetometer
SQUIDmagnetometer
Induction-coilmagnetometer(at Tampere)
FMCG
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Lead fieldLead field detecting the magnetic dipole momentdetecting the magnetic dipole moment
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J acques Fabien Gautier DAgoty:
Anatomie des parties de lagnrtion de lhomme et
de la femme. Paris, 1773.Colored mezzotint.
National Library of Medicine
Gautier DAgotys coloredmezzotints have a painterly
quality. This pregnant womancalmly looks back at the viewer,a characteristic pose of18th-century French portraiture.
The FetusThe Fetus
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Fetal ECG and MCGFetal ECG and MCGVernix Caseosa: A white, cheesy waxy substancethat coats the skin of a fetus in late pregnancy.
Fetus body, maternal abdomen:
= 5m
Vernix Caseosa: = 0.5 Mm
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Electromagnetic Method
ZE LMZMV J J i
W.R. Purvis, R.C. Tozer, I.L. Freeston, 1990
The currentIZE is fed through electrodes andthe voltage VZM from the magnetic field detector is measured.
The sensitivity is proportional tothe dot product of the lead fields.
A
_
JZE
_
JLM
B
_
JLE
_
JZM
Feeding the currentIZMto the coil andmeasuring the voltage VZEwith the electrodesgives the same sensitivity distribution.
Rod Horizontal Bipolar Amacrine Ganglion
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Electro-retino-
gram
Pigmentepithelium
RodCone
Horizontalcell
Bipolarcell
Amacrinecell
Ganglioncell
250
250
0
0 10 20 30 40 50 60 70 80 90 100
R2
a2a1a-wave
Oscillatingpotentials
Earlyreceptorpotentials
V [V]
Coneb-wave
Rodb-wave
c-wave
Time [ms]
Mlers cellMlers cell
R1