Microprocessor based Design for Biomedical Applications
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Microprocessor based Design for Biomedical Applications MBE 3 – MDBA V : Bioelectric Signals Characteristics. last Lecture: Interrupt driven Uart Communication Setup stdio- functions, printf Atmega8 Analog Digital Conveter Analog Comparator. Today:

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


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last Lecture:Interrupt driven Uart Communication

Setup stdio- functions, printf

Atmega8 Analog Digital Conveter

Analog Comparator


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Today:

Origin and characteristics of bioelectric signals

Electrodes and sensors

Review of Project exercises

Programming




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Electrical and chemical gradients

at the semi-permeable cell membrane


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Electrical and chemical gradients

at the semi-permeable cell membrane


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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


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Depolarization

Sodium Cations

rush in

Hyperpolarization

Potassom Cations

rush out


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Maintaining the

Resting potential

Sodium/potassum

Ion pump


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Voltage- and Time dependent activation of Ion Channels:

the physiological basis for action potentials

Sodium-Channel Potassum- Channel


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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


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Sodium and Potassum conductance

Calculated by the Hodkin Huxley Model (curve), measured (dots)



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Action Potentials through the membrane


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Axo-dendritic through the membrane

transmission of

action potentials,

Synaptic transduction




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Signal Pathways through the membrane

in the central nervous system


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Bioelectric Signals through the membrane


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ECG through the membraneElectro-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, …


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ECG - Electrocardiogram through the membrane


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ECG: Heart- vector, QRS Complex through the membrane



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ECG measurement: Wilson through the membrane


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Origination of the QRS - Signal through the membrane


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ECG - applications through the membrane

● Diagnostics

●Functional analysis

●Implants (pace maker)

●Biofeedback (Heartrate variability, HRV)

● Peak Performacne Training, Monitoring


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EMG - Electromyogram through the membrane



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EMG electrodes to 3mV, 1kHz)

(active)

EMG electrodes (passive)


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EMG electrodes to 3mV, 1kHz)

(active)






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EMG - applications electrode

● Rehabilitation

●Functional analysis

●active Prothetics, Orthesis

●Biomechanics, Sports medicine





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EOG - applications electrode

● Diagnostics

●Functional analysis

●Human Computer Interfaces



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EEG Electrode – cap locations of electrode the 10/20 system


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Unipolar measurement electrode( indifferential right ear electrode ) Bipolar measurement



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EEG, Alpha bursts when eyes closed, electrodealpha desynchronisation when eyes opened


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Quantitative EEG (QEEG), electrodemany EEG channels (up to 256)source / dipole localisation


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Auditory Evoked electrode

Potentials (AEP)

Trial averaging

Also:

VEP

SSEP






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Singe disk gold plated electrodes electrode

Active EEG- electrode

Ear clip electrode


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EEG - applications electrode

● Diagnostics (Epilepsy, Oncology, ..)

● Cognitive Sciences

● Sleep Analysis

● Human Computer Interfaces (BCIs)

● Pharmacology

● Intensive Care, Monitoring



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Blood pressure sensor Infrared plethysmography electrode

blood volume amplitude



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Galvanic Skin response (GSR) electrodeElectrodermal Activity (EDA)Skin Conductance Level (SCL)

peripheral body temperature


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Summary bioelectric signals electrode

Frequency Amplitude (mV)

ECG 0,2 – 300 0,1 - 3

EEG DC – 100 0,005 - 0,2

EEG (cortical) 10 – 100 0,015 - 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