biosignals eugen kvasnak, phd. department of medical biophysics and informatics 3rd medical faculty...

BioBiosignalssignals

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 cellneuron: properties, action potential, signal integration, muscle cell

Nervous a muscle excitable tissueElectroEncefaloGraphy, ElectroCardioGraphy, ElectroMyoGraphy,

ElectroRetinoGraphy, ElectroOculoGraphy, ElectroHysteroGraphy,

ElectroGasteroGraphy, MagnetoEncefaloGraphy

Another types biosignalssynaptic potentials, unit activity, population response, evoked potentials

Cell membrane

Na-K pump

Vm

Membrane Current

membran current im 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 transportPasive transportDifusion - 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 moleculeOsmosis-solvent molecules go through semipermeable membrane from low concentration site to the higher concentration site development of chemical potential

Aktivní transportAktivní 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’ transportMacro’ transportendocytosis & exocytosis

Action Potential = ALL x NOTHING

Action Potential

Action Potential = opening of sodium and potassium channels

Action Potential

K+ -channels

Na+ -channels

Vm

excitable cell

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 

EPSP a IPSP

Synaptic potentials

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

Atrial systole Ventricular systole

Heart

cardiac dipol added up the local dipols:

Heart

cardiac cycleHeart

cardiac vector field in transverse plane

MM

Heart

cardiac vector field

=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 recordingHeart

34

Eindhoven’s triangleHeart

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

Brain

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?

• ECG• EEG• EMG• EGG• ERG• …

• Temperature• Motion• pH• pO2• Chemicals• …

Other Signal Sources?

Thanks for pictures: R. Hinz, Summer School + other free web sites

Thank you for your attention!