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!