Download Heart

Biosignals
Eugen Kvasnak, PhD.
Department of Medical Biophysics and Informatics
3rd Medical Faculty of Charles University
Cell membrane and resting potential
electro-chemical activity and equilibrium, permeability, active a passive
transport, channels, osmosis
Excitable cell
neuron: properties, action potential, signal integration, muscle cell
Nervous a muscle excitable tissue
ElectroEncefaloGraphy, ElectroCardioGraphy, ElectroMyoGraphy,
ElectroRetinoGraphy, ElectroOculoGraphy, ElectroHysteroGraphy,
ElectroGasteroGraphy, MagnetoEncefaloGraphy
Another types biosignals
synaptic potentials, unit activity, population response, evoked potentials
Cell membrane
Na-K pump
Vm
Membrane Current
im
membran current im
t
time / ms
distance / mm
Cytoplasmic membrane (or plasmalema)
Function:
• selective transport between cell and vicinity
• contact and mediation of information between cell and vicinity
Structure:
• thin semi-permeable cover surrounding the cell
• consists from one lipid double-layer and proteins anchored in there
lipid double-layer … gives basic physical features to plasmalema
… on / in: floating or anchored proteins (ion channels)
proteins … anchored in lipid double-layer in different ways
… give biological activity and specificity to plasmalema
glykokalyx … protective cover of some cells formed of oligosacharides,
… there are receptors, glykoproteins and other proteoglikans
… protects against chemical and mechanical damage
Material transport across the cytoplasmic membrane
Pasive transport
Difusion
- free transport of small non-polar molecules across membrane
Membrane channel
- transmembrane protein
- transport is possible without additional energy
- cell can regulate whether it is open or not (deactivated)
- channel is specific for particular molecule
Osmosis
-solvent molecules go through semipermeable membrane from low concentration site
to the higher concentration site  development of chemical potential
Aktivní transport
- cell has to do a work (in form of chemical energy, mostly ATP) for transportation
- it’s done by pumps, plasmatic membrane protein anchored in both lipid layers (e.g.
Na+-K+-ATPase)
- result of ion transport  different ion concentration in/out cell  electric potential
‘Macro’ transport
endocytosis & exocytosis
Action Potential = ALL x NOTHING
Action Potential
Action Potential = opening of sodium and potassium channels
Action Potential
excitable cell
Vm
Na+ -channels
K+ -channels
time
resting potential
equivalent Current Dipole
Active and Passive Transport 
 chemical (concentration) + electric gradient 
 electro-chemical
potential on membrane
!!! Cell INSIDE is NEGATIVE compare to OUTSIDE
(in rest usually –75mV)
Excitable cell: NEURON
structure:
 dendrites with synapses
 body
 axon with myelin and synapses
function:
 thresholding of input signals
 integration (temporal and
spacial) of input signals
 generation of action potentials
Synapse
Synapse
HOW to measure potentials ?
by electrodes - intracellular,
- extracellular,
- superficial
indirectly – by recording of charge spread ... probes
(e.g. fluorescence)
FROM WHERE to measure potentials ?
- from whole body, organ, tissue slices, tissue
culture, isolated cell
Types of biosignals
Synaptic potentials – excitatory pre- / post-synaptic potentials,
inhibitory pre- / post-postsynaptic potentials
mostly they don’t cause AP because of weak
time and spacial summations (correlation)
… they don’t reach threshold for AP
Unit activity – activity of one neuron, ACTION POTENTIALS
Population response – summary response of neuronal population
APs of thousands of neurons
Evoked potentials – response of sensory pathway to the stimulus
Synaptic potentials
EPSP a IPSP
Synaptic potentials
Unit activity vs. Population response
Evoked potentials
… averaged signal of many cells
… recorded from:
Cerebral cortex
Brainstem
Spinal cord
Peripheral nerves
…
Excitable cell: NEURON and MUSCLE CELL
Striated muscles
skeletal muscle – controlled by CNS via moto-neurons
heart muscle - not controlled by CNS
- refractory phase is longer than contraction
(systolic) a relaxation (diastolic) time
Smooth muscles – not controlled by CNS, but by autonomic system
Heart
Heart
Atrial systole
Ventricular systole
Heart
cardiac dipol added up the local dipols:
Heart
cardiac cycle
Heart
cardiac vector field in transverse plane
M
Heart
cardiac vector field
j =const
Heart
ElectroCardioGram
Change of electric potential
 heart muscle activation
 atrium depolarization
3 diff. recording schemes:
Einthoven, Goldberger, Wilson
Frequency = 1-2 Hz !
Heart
2-dimensional recording
Heart
Eindhoven’s triangle
34
Brain
ElectroEncefaloGram
Waves:
•Delta: < 4 Hz
... sleeping, in awakeness pathological
•Theta: 4.5 -8 Hz
... drowsiness in children, pathological in aduls
(hyperventilation, hypnosis, ...)
•Alfa: 8.5 -12 Hz
... relaxation physical / mental
•Beta: 12 - 30 Hz
... wakefulness, active concentration
•Gama: 30–80 Hz
…higher mental activity including perception and
consciousness
Biosignals Recording:
ElectroMyoGraphy – electric activity of skeletal muscles
ElectroRetinoGraphy – electric activity of retina
ElectroOculoGraphy – electric activity of eye movements
ElectroHysteroGraphy – electric activity of hystera (uterus)
ElectroGasteroGraphy – electric activity of stomach
MagnetoEncephaloGraphy – electric activity of brain
...
Other Biopotentials?
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ECG
EEG
EMG
EGG
ERG
…
Other Signal Sources?
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Temperature
Motion
pH
pO2
Chemicals
…
Thanks for pictures:
R. Hinz, Summer School + other free web sites
Thank you for your attention!