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 VmVm

Membrane Current membran current i m imim 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 K + -channels Na + -channels VmVm excitable cell time resting potential

proceeding AP in MUSCLE

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

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

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 systoleVentricular systole Heart

cardiac dipol added up the local dipols: Heart

cardiac cycle Heart

cardiac vector field in transverse plane M 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 recording Heart

34 Eindhoven’s triangle Heart

ElectroEncefaloGram Waves: Delta: < 4 Hz... sleeping, in awakeness pathological Theta: Hz... drowsiness in children, pathological in aduls (hyperventilation, hypnosis,...) Alfa: Hz... relaxation physical / mental Beta: 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!