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


last Lecture:Interrupt driven Uart Communication

Setup stdio- functions, printf

Atmega8 Analog Digital Conveter

Analog Comparator


Today:

Origin and characteristics of bioelectric signals

Electrodes and sensors

Review of Project exercises

Programming




Electrical and chemical gradients

at the semi-permeable cell membrane


Electrical and chemical gradients

at the semi-permeable cell membrane


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


Depolarization

Sodium Cations

rush in

Hyperpolarization

Potassom Cations

rush out


Maintaining the

Resting potential

Sodium/potassum

Ion pump


Voltage- and Time dependent activation of Ion Channels:

the physiological basis for action potentials

Sodium-Channel Potassum- Channel


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


Sodium and Potassum conductance

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



Action Potentials through the membrane


Axo-dendritic through the membrane

transmission of

action potentials,

Synaptic transduction




Signal Pathways through the membrane

in the central nervous system


Bioelectric Signals through the membrane


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, …


ECG - Electrocardiogram through the membrane


ECG: Heart- vector, QRS Complex through the membrane



ECG measurement: Wilson through the membrane


Origination of the QRS - Signal through the membrane


ECG - applications through the membrane

● Diagnostics

●Functional analysis

●Implants (pace maker)

●Biofeedback (Heartrate variability, HRV)

● Peak Performacne Training, Monitoring


EMG - Electromyogram through the membrane



EMG electrodes to 3mV, 1kHz)

(active)

EMG electrodes (passive)


EMG electrodes to 3mV, 1kHz)

(active)






EMG - applications electrode

● Rehabilitation

●Functional analysis

●active Prothetics, Orthesis

●Biomechanics, Sports medicine





EOG - applications electrode

● Diagnostics

●Functional analysis

●Human Computer Interfaces



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


Unipolar measurement electrode( indifferential right ear electrode ) Bipolar measurement



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


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


Auditory Evoked electrode

Potentials (AEP)

Trial averaging

Also:

VEP

SSEP






Singe disk gold plated electrodes electrode

Active EEG- electrode

Ear clip electrode


EEG - applications electrode

● Diagnostics (Epilepsy, Oncology, ..)

● Cognitive Sciences

● Sleep Analysis

● Human Computer Interfaces (BCIs)

● Pharmacology

● Intensive Care, Monitoring



Blood pressure sensor Infrared plethysmography electrode

blood volume amplitude



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

peripheral body temperature


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


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