Bioelectric potentials
- 1. Bioelectric potentials Mrs.V.SrirengaNachiyar, AP/ECE Ramco Institute of Technology Academic Year: 2017-2018 (Even)
- 2. Bioelectric potentials • To measure bioelectric potentials, a transducer capable of converting ionic potentials and currents into electric potentials and currents is required. • Such a transducer consists of two electrodes which measure the ionic potential difference between their respective points of application.
- 3. Electrocardiogram (ECG) • Bio potentials generated by the muscles of the heart results In Electrocardiogram. • ECG bio-signal typical specifications: • low differential voltage from 0.4 to 3 mV • high common-mode rejection ratio level • low frequency range • high noise
- 5. DESCRIPTION • Heart is divided into four chambers • Two upper chambers- left & right atria • Two lower chambers-left & right ventricles • Right atrium receives blood from the veins of the body & pumps into right ventricle • Oxygen enriched blood then enters the left atrium from which it is pumped into the left ventricle • Electrodes: A conductor through which electricity enters or leaves an object, substance, or region
- 7. Cont… • Each action potential in the heart originates near the top of the right atrium at a point called the pacemaker or Sinoatrial node (SA) • Pacemaker- A group of specialized cells that spontaneously generate action potentials at a regular rate. • To initiate the heart beat, the action potentials generated by the pacemaker propagate in all directions along the surface of both atria
- 8. Cont… • The wave terminates at a point near the center of the heart are called the Atrioventricular (AV) node. • At this point, some special fibers act as a delay line to provide proper timing between the action of atria & ventricles. • Once the electrical excitation has passed through the delay line, it is rapidly spread to all parts of both ventricle by the bundle of hiss called purkinje fibers, used to initiate action potentials.
- 10. Cont…. • P-wave: represents the depolarization of the atrial musculature • QRS Complex: combined result of repolarization of the atria and depolarization of ventricles • T-wave: wave of ventricular repolarization • U-wave: the result of after potentials in the ventricular muscles.
- 11. Electroencephalogram (EEG) • Measures neuronal activity of the brain • Waveform varies according to the location of measuring electrodes on the surface of the scalp • For wide-awake person- unsynchronized high frequency EEG • For drowsy person-produces large amount of rhythmic activity in the range 8-13Hz • For asleep person-amplitude & frequency of waveform decreases.
- 12. Cont…. • Light sleep-large amount of amplitude & low frequency waveform • Deeper sleep- even slower and higher amplitude waves EEG Frequency bands: Below 3 ½ Hz – Delta From 3 ½ to 8Hz - Theta From 8 to 13Hz - Alpha Above 13Hz - Beta
- 13. EMG- Electromyogram • Bioelectric potentials associated with muscle activity • It may measured at the surface of the body near a muscle of interest or directly from the muscle by penetrating the skin with needle electrodes • EMG electrodes pickup potentials from all muscles • EMG waveforms appears very much like a random-noise waveform
- 14. Cont… • The amplitude of measured EMG waveform is the instantaneous sum of all the action potentials generated at any given time. • Because these action potentials occur in both positive & negative polarities at a given pair of electrodes
- 15. Other Bioelectric potentials • ERG (Electroretinogram) – A record of complex pattern of bioelectric potentials obtained from the retina of eye • EOG (Electro-Oculogram) – a measure of variations in the corneal retinal potential as affected by the position of the eye • EGG (Electrogastrogram) – associated with the peristaltic movements of the gastroretinal tract
- 16. References • Leslie Cromwell, “Biomedical Instrumentation and Measurement”, Prentice Hall of India, New Delhi, 2007. • John G.Webster, “Medical Instrumentation Application and Design”, 3rd Edition, Wiley India Edition, 2007 • Khandpur, R.S., “Handbook of Biomedical Instrumentation”, TATA Mc Graw-Hill, New Delhi, 2003. • M. Arumugam,” Biomedical Instrumentation”, Second Edition.