gtu topic 2_sources of bioelectric potentials

COMPILED BY: Prof G B RathodET department-BVM College,

Email: ghansyam.rathod@bvmengineering.

ac.in

SOURCES OF BIOELECTRIC POTENTIALS

04/18/2023BVM, ET, Biomedical Instrumentation(171006)

OutlineIntroductionResting and action potentialsPropagation of action potentialsThe bioelectric potentialsOutcomesReferenceQuestions

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IntroductionBioelectric Potentials: for various functions, body

generate their own monitoring signals which contain some useful information.

These signals are bioelectric potentials associated with nerve conduction, brain activity, heartbeat, muscle activity and so on.

Its an ionic voltages and its produced by certain electrochemical activity by special types of cells. Transducers can convert this ionic to electrical voltages.

First time Italian Professor, Luigi Galvani(1786), claim that he found electricity in muscle of a frog’s leg. In human 1903 by Dutch physician willem Einthoven.

Development of semiconductor electronics, the research made easy.

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Resting and Action PotentialsCertain types of cells such as nerve and

muscle cells are encased in semipermeable membrane.

Surrounding the cell contain body fluids which is conductive solution having charged atoms kwon as atoms.

The principal Ions are sodium(Na+), Potassium(K+), and Chloride(CL-).

Cell Membrane allows K+ and Cl- to enter inside but blocks the Na+

Because of that more Na+ outside and Cl- and K+ inside. Due to less K+ , outside cell shows + and inside is -.

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Resting and Action Potentials

Polarized cell with its resting potential

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Resting and Action PotentialsEquilibrium is reached with a potential difference across

the membrane, negative on the inside and positive on the outside.

This membrane potential is called the “Resting Potential” of the cell and maintained until some kind of disturbance upset the equilibrium.

Research provided the value ranging from -60 mV to -100 mV. A Cell in the resting state is said to be polarized.

When a section of a cell membrane is excited by the flow of ionic current or by some form of externally applied energy,, the membrane allows some Na+ and try to reach some balance of potential inside and outside. Same time the some K+ goes outside but not rapidly like sodium.

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Fig: Depolarization of a cell.

•As a result, the cell has slightly Positive potential on the inside Due to the imbalance of the Potassium ions.•This potential is known as “action Potential” and is approximately +20 mV.•A cell that has been excited and that displays an action potential is said to be depolarized and process from resting to action potential is called depolarization

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Fig: Depolarization cell during an action potential

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With in short time once again cell try to Be in resting state.

Waveform of the action potential

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Resting and Action PotentialsThe time scale depends on the cell producing the potential. In nerve and muscle cells, repolarization occur as spike

around 1 msec total duration. Heart muscle need 150 to 300 msec.

Regardless of the method by which cell is excited or the intensity of the stimulus, the action potential is always the same for any given cell. This is known as the all-or-nothing law.

The small period of time where the cell can not respond to any new stimulus is known as a absolute refractory period, last for 1 msec in nerve cells.

Following the absolute refractory period, there occurs a relative refractory period, during which another action potential can be triggered but much stronger stimulation is required.

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Propagation of action potentialsThe rate at which an action potential

moves down a fiber or is propagate from cell to cell is called the propagation rate.

In nerve fiber the propagation rate is also called the nerve conduction rate, or conduction velocity. Velocity range in nerves is from 20 to 140 meters per second.

In heart muscle, the rate is slower, average 0.2 to 0.4 m/sec

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The Bioelectric Potentials

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The Electrocardiogram(ECG)The Electroencephalogram(EEG)The Electromyogram(EMG)The Electroretinogram(ERG)The Electro-oculogram(EOG)The Electrogastrogram(EGG)



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The Electrocardiogram(ECG)The bio-potentials generated by the

muscles of the heart result in the electrocardiogram(ECG). German word EKG

To understand the ECG generation, Need to understand the anatomy of the heart.



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Right atrium tricuspid valve right ventricle

Right ventricle pulmonary semilunar valve pulmonary arteries lungs

Lungs pulmonary veins left atriumLeft atrium bicuspid valve left ventricleLeft ventricle aortic semilunar valve

aortaAorta systemic circulation



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Electrical activity is recorded by electrocardiogram (ECG)

P wave corresponds to depolarization of SA node

QRS complex corresponds to ventricular depolarization

T wave corresponds to ventricular repolarization

Atrial repolarization record is masked by the larger QRS complex



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The Electroencephalogram(EEG)The recorded representation of bioelectric

potential by the neuronal activity of the brain is called the electroencephalogram.

The waveform varies greatly with the location of the measuring electrodes on the surface of the scalp.



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Frequency Range Signal Type Activity

Below 3.5 Hz Delta Deep sleep

From 3.5 Hz to about 8 Hz

Theta Fall aslpeep

From about 8 Hz to about 13 Hz

Alpha Drowsy person

Above 13 Hz Beta Paradoxial sleep, Rapid eye movement(REM)



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EMG: The bioelectric potentials associated with muscle activity constitute the electromyogram.

Can be measure on the surface of the body or by penetrating the skin using needle electrodes.


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ERG: Eelctoretinogram: A record of the complex pattern of the bioelectric potentials obtain from the retina of the eye. This is usually a response to a visual stimulas.

EOG: Electro-oculogram: A measure of the variation in the corneal-retinal potential as affected by the position and movement of eye.

EGG:Electrogastrogram: The EMG patterns associated with the peristaltic movement of the gastrointestinal tract.


Outcomes

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The basic of potential generation from the body

Understanding of basic concept of various bioelectric signals from the human body.


References

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Book: “Biomedical instrumentation and measurements “ ,by L. Cromwell, F .Weibell, and E. Pfeiffer. PHI publication 2nd Edition

www.msu.edu/anatomywww.humbleisd.net/cms/.../Anatomywww.lavc.edu/instructor/...k/.../Lectureweb.as.uky.edu/Biology/faculty

http://www.msu.edu/anatomy

http://www.humbleisd.net/cms/.../Anatomy

http://www.humbleisd.net/cms/.../Anatomy

http://www.lavc.edu/instructor/...k/.../Lecture


Questions?????

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Thank you

gtu topic 2_sources of bioelectric potentials

Engineering

resting potential

action potentials fig

action potentials equilibrium

cell membrane

membrane potential

depolarization cell

resting state

positive potential