Chapter -The Origin of Bio potentials Anotomy Unit I Chapter -The Origin of Bio potentials Anotomy

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 Passive 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 resting potential time Na+ -channels K+ -channels 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

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

skeletal muscle – controlled by CNS via moto-neurons 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

cardiac dipol added up the local dipols: Heart cardiac dipol added up the local dipols:

Heart cardiac cycle

cardiac vector field in transverse plane 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 !

2-dimensional recording Heart 2-dimensional recording

Heart Eindhoven’s triangle

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 ...

Electroneurogram (ENG) Recording the field potential of an excited nerve. Neural field potential is generated by - Sensory component - Motor component Parameters for diagnosing peripheral nerve disorder Conduction velocity Latency Characteristic of field potentials evoked in muscle supplied by the stimulated nerve (temporal dispersion) Amplitude of field potentials of nerve fibers < extracellular potentials from muscle fibers.

Field Potential of Sensory Nerves Extracellular field response from the sensory nerves of the median or ulnar nerves To excite the large, rapidly conducting sensory nerve fibers but not small pain fibers or surrounding muscle, apply brief, intense stimulus ( square pulse with amplitude 100-V and duration 100-300 sec). To prevent artifact signal from muscle movement position the limb in a comfortable posture. Figure 4.8 Sensory nerve action potentials evoked from median nerve of a healthy subject at elbow and wrist after stimulation of index finger with ring electrodes. The potential at the wrist is triphasic and of much larger magnitude than the delayed potential recorded at the elbow. Considering the median nerve to be of the same size and shape at the elbow as at the wrist, we find that the difference in magnitude and waveshape of the potentials is due to the size of the volume conductor at each location and the radial distance of the measurement point from the neural source.

Reflexly Evoked Field Potentials Some times when a peripheral nerve is stimulated, a two evoked potentials are recorded in the muscle the nerve supplies. The time difference between the two potentials determined by the distance between the stimulus and the muscle. Stimulated nerve: posterior tibial nerve Muscle: gastrocnemius