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Microprocessor-based Design for Biomedical Applications

This lecture discusses the origin and characteristics of bioelectric signals, electrodes and sensors, programming, and the physiological basis for action potentials. It also covers topics such as nerve cells, signal pathways in the central nervous system, and various bioelectric signal measurements including ECG, EMG, EOG, and EEG.

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Microprocessor-based Design for Biomedical Applications

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  1. Microprocessor based Design for Biomedical ApplicationsMBE 3 – MDBAV : Bioelectric SignalsCharacteristics

  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

  8. Nernst – equation (chemical potential): R … Gas-Constant = 8,3143 J / (mol·K) T … Temperature (Kelvin) 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. Voltage- and Time dependent activation of Ion Channels: the physiological basis for action potentials Sodium-Channel Potassum- Channel

  12. Hodgkin - Huxley Model (1952) ●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 Alan Hodgkin Andrew Huxley

  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 activityEMG Electro-Myogram, Muscle movementEOG Electro-Oculogram, Eye movementEEG Electro-EncephalogramGSRGalvanic 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 (active) EMG electrodes (passive)

  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

  44. EEG, dominant frequencies, < 300 uV

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

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

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

  48. EEG artifacts: Eye blinks, muscle tension

  49. EEG artifacts: movement, electrode drifting

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