Sources of bioelectric potentials

The Action and resting potential of the body are discussed. The working of body cell, tissue and how the electrical activity of body cell done? are discussed.

1. COMPILED BY: Prof G B Rathod
EC department-BVM College,
Email: [email protected]

SOURCES OF BIOELECTRIC
POTENTIALS

2. Outline
Introduction
Resting and action potentials
Propagation of action potentials
The bioelectric potentials
Outcomes
Reference
Questions
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3. Introduction
Bioelectric 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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4. Resting and Action Potentials
Certain 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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5. Resting and Action Potentials
Polarized cell with its resting potential
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6. Resting and Action Potentials
Equilibrium 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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7. Resting and Action Potentials
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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8. Resting and Action Potentials
Fig: Depolarization cell during an action potential
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9. Resting and Action Potentials
With in short time once again cell try to
Be in resting state.
Waveform of the action potential
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10. Resting and Action Potentials
The 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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11. Propagation of action potentials
The 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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12. 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)

13. The Bioelectric Potentials
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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.

14. The Bioelectric Potentials
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15. The Bioelectric Potentials
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Right atrium  tricuspid valve  right ventricle
Right ventricle  pulmonary semilunar valve  pulmonary
arteries  lungs
Lungs  pulmonary veins  left atrium
Left atrium  bicuspid valve  left ventricle
Left ventricle  aortic semilunar valve  aorta
Aorta  systemic circulation

16. The Bioelectric Potentials
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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

17. The Bioelectric Potentials
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18. The Bioelectric Potentials
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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.

19. The Bioelectric Potentials
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20. The Bioelectric Potentials
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21. The Bioelectric Potentials
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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)

22. The Bioelectric Potentials
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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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24. The Bioelectric Potentials
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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.

25. 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.

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

Edition
www.msu.edu/anatomy
www.humbleisd.net/cms/.../Anatomy
www.lavc.edu/instructor/...k/.../Lecture
web.as.uky.edu/Biology/faculty

27. Questions?????
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Thank you