1. Microprocessor based Design for Biomedical Applications MBE 3 – MDBA V : Bioelectric Signals Characteristics

2. last Lecture: Interrupt driven Uart Communication Setup stdio- functions, printf Atmega8 Analog Digital Conveter Analog Comparator

3. Today: Origin and characteristics of bioelectric signals Electrodes and sensors Review of Project exercises Programming

4. Origin of Bioelectric Signals

5. Cell membrane, channel proteines

6. Electrical and chemical gradients at the semi-permeable cell membrane

7. Electrical and chemical gradients at the semi-permeable cell membrane IonesIntracel.extracel. potassum K + 40020 Sodium Na + 50440 Chlorid Cl - 108560 organic Aniones 4600

8. R … Gas-Constant = 8,3143 J / (mol·K) T … Temperature (Kelvin) Nernst – equation (chemical potential): Goldman – equation (for different ions): As a result, we get a membrane resting potential of about -70mV

9. Depolarization Sodium Cations rush in Hyperpolarization Potassom Cations rush out

10. Maintaining the Resting potential Sodium/potassum Ion pump

11. Sodium-Channel Potassum- Channel Voltage- and Time dependent activation of Ion Channels: the physiological basis for action potentials

12. Hodgkin - Huxley Model (1952) Alan Hodgkin Andrew Huxley ● Researched the Giant Squid-Axon ● Used the Voltage-Clamp technique -> Isolation of channel currents of Na und K ● Developed a model for the function of the channel proteines

13. Sodium and Potassum conductance Calculated by the Hodkin Huxley Model (curve), measured (dots)

14. Action potential: the result of Na and K Ion movement through the membrane

15. Action Potentials

16. Axo-dendritic transmission of action potentials, Synaptic transduction

17. Synaptic coupling, release and uptake of neurotransmitters

18. Types of nerve cells, Synaptic coupling

19. Signal Pathways in the central nervous system

20. Bioelectric Signals

21. ECG Electro-Cardiogram, Heart activity EMG Electro-Myogram, Muscle movement EOG Electro-Oculogram, Eye movement EEG Electro-Encephalogram GSR Galvanic Skin Response ● Measured with electrodes: skin-electrode interface: Ions Electrodes Breathing, temperature, movement etc. ● Measured with other sensors / transducers: NTC, LDR, piezo-crystal, hall-sensor, Accelerometer, Goniometer, …

22. ECG - Electrocardiogram

23. ECG: Heart- vector, QRS Complex

24. ECG measurement: Goldberger (left) and Einthoven (right)

25. ECG measurement: Wilson

26. Origination of the QRS - Signal

27. ECG - applications ● Diagnostics ● Functional analysis ● Implants (pace maker) ● Biofeedback (Heartrate variability, HRV) ● Peak Performacne Training, Monitoring

28. EMG - Electromyogram

29. EMG surface (glue-) electrodes EMG - signal (up to 3mV, 1kHz)

30. EMG electrodes (passive) EMG electrodes (active)

31. EMG electrodes (active)

32. Recording locations for facial EMG

33. Needle electrodes adhesive electrode

34. Vagina / rectal electrodes / pelvic floor training

35. EMG activity: averaging absolute vaues

36. EMG - applications ● Rehabilitation ● Functional analysis ● active Prothetics, Orthesis ● Biomechanics, Sports medicine

37. EMG - Electrooculogram

38. Electrooculogram (EOG), Eye Dipole

39. Saccadic eye movements to the left and right

40. EOG - applications ● Diagnostics ● Functional analysis ● Human Computer Interfaces

41. EEG - Electroencephalogram

42. EEG Electrode – cap locations of the 10/20 system

43. Unipolar measurement ( indifferential right ear electrode ) Bipolar measurement

45. EEG, dominant frequencies, < 300 uV

46. EEG, Alpha bursts when eyes closed, alpha desynchronisation when eyes opened

47. Quantitative EEG (QEEG), many EEG channels (up to 256) source / dipole localisation

48. Auditory Evoked Potentials (AEP) Trial averaging Also: VEP SSEP

49. EEG artifacts: Eye blinks, muscle tension

50. EEG artifacts: movement, electrode drifting

51. EEG artifacts: mains interference, 50/60Hz noise

52. Intracortical / chronical electrodes

53. Active EEG- electrode Singe disk gold plated electrodes Ear clip electrode

54. EEG - applications ● Diagnostics (Epilepsy, Oncology,..) ● Cognitive Sciences ● Sleep Analysis ● Human Computer Interfaces (BCIs) ● Pharmacology ● Intensive Care, Monitoring

55. Other (nonelectric) Biosignals

56. Blood pressure sensor Infrared plethysmography blood volume amplitude

57. Breathing Sensors (thermal / mechanoresistive)

58. Galvanic Skin response (GSR) Electrodermal Activity (EDA) Skin Conductance Level (SCL) peripheral body temperature

59. Summary bioelectric signals Frequency Amplitude (mV) ECG 0,2 – 300 0,1 - 3 EEG DC – 1000,005 - 0,2 EEG (cortical) 10 – 1000,015 - 0,3 EMG 10 – 1000 0,1 - 5 EMG (needle)10 – 10000 0,05 - 5 EOG 0 – 30 0,1 - 2 Intracell. 0 – 10000 50.. 130