Transcript 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? • • • • • • ECG EEG EMG EGG ERG … Other Signal Sources? • • • • • • Temperature Motion pH pO2 Chemicals … Thanks for pictures: R. Hinz, Summer School + other free web sites Thank you for your attention!