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Prof. Dr. Nizamettin AYDIN

[email protected]@ieee.org

http://www.yildiz.edu.tr/~naydin

Biomedical Instrumentation

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mailto:[email protected]:naydin@imailto:naydin@imailto:naydin@imailto:naydin@imailto:[email protected]:[email protected]:[email protected]:[email protected]

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Resting and action potentials

The resting potential is the result of an unequaldistribution of ions across the membrane.

The resting potential is sensitive to ions inproportion to their ability to permeate the

membrane.

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Resting potentials

Forget the membrane and consider what factorsdetermine the movement of ions in solution.

Aqueous diffusionand

Electrophoretic movement

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0 mV

Resting potentials

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0 mV

Resting potentials

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-80 mV

Resting potentials

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++

+

+

+

+

+

-

-

-

-

-

-

-80 mV

Resting potentials

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++

+

+

+

+

+

-

-

-

-

-

-

-80 mV

[K+] = 2.5

[Na+] = 125[Cl-] = 130

A-

[K+] = 135

[Na+] = 7

[Cl-] = 11

A-

Resting potentials

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Resting potentials

Resting membrane potential

is independent of externalNa+ concentration

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Resting potentials

Resting membrane potential

strongly depends upon the

external K+ concentration

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Summary

The membrane conducts ions very poorly and allows the

separation of ionic species. This results in a potential difference between the outside and the inside

of the membrane.

The magnitude of the resting potential is determined by theselective permeability of the membrane to ionic species.

We can quantify the magnitude of the resting potential byconsidering both the diffusive and electrophoretic properties.

In order to understand the time dependence and individualcontributions of ionic species to the membrane potential it isconvenient to use an electrical equivalent circuit.

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Resting Membrane Potential

Membrane

outside

inside

Na+

Na+

Cl-

Cl-K+

K+

A-

+ + + + + + + + + + +

-----------

+ + + + + + + + + + +

-----------

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Membrane is polarized

more negative particles in than out Bioelectric Potential

like a battery

Potential for ion movement current ~

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INSIDE

POS

NEG

Bioelectric PotentialOUTSID

E

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Questions

What is the Bioelectric potentials? What is Membrane is polarization?

Draw a graph of Resting membrane potential ?

What are Resting Membrane Potential? Explain PROPOGATION OF POTENTIALS ?

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Frequencies of Biopotentials

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Electrocardiogram (ECG)

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Recording System EEG

EEG recording is done

using a standard lead

system called 10-20system

Recall dipole concept

to identify source of

brain activity

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Electromyogram (EMG)

Measures muscle activity Recordintramuscularly through needle

electrodes

Record surface EMG using electrodes onbiceps,triceps

Use in muscular disorders,muscle based

prosthesisprosthetic arm, leg

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Electroretinogram Electroretinogram (ERG)

Biopotential of the eye (retina) Indicator of retinal diseases such as retinal

degenration, macular degernation

Invasive recording

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Questions

What is Electroretinogram Electroretinogram ?

What is EEG?

Draw a graph of Resting membrane potential ?

What are the Frequencies of Biopotentials?

Explain EMG

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E d

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KINDS OF ELECTRODES

Eectrodes

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E t d

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Eectrodes

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Figure A disposable surface electrode. A typical surface electrode used for ECG

recording is made of Ag/AgCl. The electrodes are attached to the patients skin

and can be easily removed.

Eectrodes

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S i Bi di l

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May include

sensors (for measurement)

actuators (for doing work)

displays

sensor

Actuators

POWER/PRESSURE

Displays

Sensors in Biomedical

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Transducer Systems

Sensors

Actuators

Interface

Circuits

Control

and

Processing

Circuits

PowerSupply

I/O Channel

/USER

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Cl ifi ti f T d

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Classification of Transducers

Transducers

On The Basis of

principle UsedActive/Passive Primary/Secondary Analogue/Digital

Capacitive

Inductive

Transducers/

Inverse Transducers

Transducers may be classified

according to their application, method of

energy conversion, nature of the output

signal, and so on.

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Resistive

Q ti
http://localhost/var/www/apps/conversion/tmp/faculty/Desktop/new/LECTURE%2011.ppthttp://localhost/var/www/apps/conversion/tmp/faculty/Desktop/new/LECTURE%2011.ppthttp://localhost/var/www/apps/conversion/tmp/faculty/Desktop/new/LECTURE%2011.ppthttp://localhost/var/www/apps/conversion/tmp/faculty/Desktop/new/LECTURE%2011.ppt

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Questions

What is bio-potential ELECTRODES?

What Transducer Systems?

What are the KINDS OF ELECTRODES?

Explain Classification of Transducers

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