Biopotentials are ionic voltages produced by electrochemical activity in cells. Certain cells like nerve and muscle cells are encased in a semi-permeable membrane that allows some substances to pass through while keeping others out. These membranes maintain a resting potential of -60 to -100 mV by allowing potassium and chloride ions into the cell while blocking sodium ions. When the membrane allows sodium ions to pass through, the cell's potential becomes slightly positive in what is called an action potential, changing the cell from its resting state. Transducers are used to convert these ionic potentials into electrical signals that can be measured and analyzed.

1. Origin of Biopotentials
Mr.A.Rameshbabu AP/ECE
Ramco Institute of Technology
Academic Year 2017 – 2018 (Even)

2. Origin of Biopotentials
The systems in the human body generate their own
monitoring signals when they carry out their
functions.
These signals provide useful information about their
function.
Bioelectric potentials are actually ionic voltages
produced as a result of electro chemical activity of
certain cell.
Transducers are used to convert these ionic potentials
in to electrical signals.

3. Resting and Action potentials
Certain types of cells within the body such as nerve
and muscle cells are encased in a semi permeable
membrane.
This membrane permits some substances to pass
through while others are kept out.
Surrounding the cells of the body are the body fluids.
These fluids are conductive solutions containing
charged atoms known as ions.

4. The principle ions are sodium(Na+), Potassium(K+)
and chloride(C-)
The membrane of excitable cells permit entry of
Potassium(K+) and chloride(C-) ions but blocks the
entry of sodium(Na+) ions.
So inside the cell is more negative than outside cell
This membrane potentials is called Resting potentials.
This resting potential ranging from -60mv to -100 mv.
Cell in the resting state is called polarized cell.
After that the membrane change its characteristics
and start allow sodium(Na+) ions to pass through it.

5. Now the cell has slightly positive potential on the
inside. This potential is called Action potential.
The process of changing from the resting state to the
action potential is called Depolarization.

6. Heart

8. Electrocardiogram (ECG)

9. Electroencephalogram (EEG)

10. Electroencephalogram (EEG)

12. Electromyogram (EMG)

13. Electroretinogram (ERG)

14. Reference
Leslie Cromwell, “Biomedical
Instrumentation and Measurement”,
Prentice Hall of India, New Delhi,
2007.