Upload
george-goodwin
View
223
Download
0
Tags:
Embed Size (px)
Citation preview
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!