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2nd practice Medical Informatics Biomedical Signal Processing TAMUS, Zoltán Ádám

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Presentation on theme: "2nd practice Medical Informatics Biomedical Signal Processing TAMUS, Zoltán Ádám"— Presentation transcript:

1 2nd practice Medical Informatics Biomedical Signal Processing TAMUS, Zoltán Ádám

2  Action potential  Electroneurogram (ENG)  Electromyogram (EMG)  Electrocardiogram (ECG)  Electroencephalogram (EEG)  Electrogastrogram (EGG)  Phonocardiogram (PCG)  Carotid Pulse (CP)  Vibromyogram (VMG)  Vibroarthogram (VAG)

3  Basic component of bioelectrical signals  Caused by the flow of Na +, K + and Cl - ions across the cell membrane

4  Resting potential: In their resting state, the membrane readily permit the entry of K + and Cl - ions, but effectively block the entry of Na + ions. The permeability of membrane for K + is times that for Na + ions. A cell in resting state is said to be polarized. The resting potential is in order of -60 to -100 mV

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6  Depolarization: When a cell is excited the membrane changes its characteristics and begins to allow Na + ions to enter the cell. This movement of Na + ions constitutes an ionic current, which further reduces the membrane barrier to Na + ions. This leads to an avalache effect: Na + ions rush into the cell. The inside of the cell becomes positive. The peak value of action potential is about 20 mV

7  Repolarization: Membrane depolarization also increases the permeability of membrane for K + ions via a voltage-dependent K + channels. The permeability of membrane for Na + ions decrease near the peak of depolarization. The efflux of K + ions from the cell makes the inside more negative thereby effecting repolarization back to the resting potential. Duration in nerve and muscle cells ~1 ms, in heart muscle cells ms

8  All-or-none phenomenon  Absolute refractory period: 1 ms in nerve cells  Relative refractory period: several ms in nerve cells

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11  The ENG is an electrical signal observed as a stimulus and the associated nerve action potential propagate over the length of nerve.  ENGs may be recorded using contcentric needle electrodes or Ag-AgCl electrodes at the surface of the body.  In order to minimize muscle contraction strong but short stimulus is applied (100 V amplitude, μ s).  ENGs have amplitudes of the order of 10 μ V.

12  Wirst  BElbow - below the elbow  AElbow – above the elbow

13  Typical values of propagation rate or nerve conduction velocity are: m/s in nerve fibers m/s in heart muscle m/s in time delay fibers between the atria and ventricles.  Neural diseases may cause a decrease in conduction velocity.

14  Motor units  Single Motor Unit Action Potential (SMUAP)

15  Normal SMUAPs are usually biphasic or triphasic  3-15 ms in duration, μ V in amplitude, 6-30 Hz in frequency range

16  The system of electrode placement for EEG recording.

17  The commonly used terms for EEG frequency range: Delta (0.5-4 Hz): deep sleep Theta (4-8 Hz): beginning stages of sleep Alpha (8-13 Hz): principal resting rhythm Beta (>13 Hz): background activity in tense and anxious subjects

18  a: delta, b: theta, c: alpha, d: beta, e: blocking of alpha rhythm by eye opening, f: marker 50 μ V, 1 sec

19  The electrical activity of the stomach consists of rhytmic waves of depolarization and repolarization of its constituent smooth muscle cells.  The activity originates in the mid-corpus of the stomach, with intervals of about 20 s in human.  Recorded by abdomen electrodes e.g. three electrodes along the antral axis of stomach and the common reference electrode

20  The CP is a pressure signal recorded over the carotid artery.  Parts of CP: P (percussion wave): ejection of blood from the left ventricle T (tidal wave): reflected pulse from the upper body D (dicrotic notch): closure of the aortic valve DW (dicrotic wave): reflected pulse from the lower body

21  Direct mechanical manifestation of contraction of a skeletal muscle.  Accompanies the EMG  Recorded by contact microphones or accelerometers placed on the muscle surface.

22  The VAG is the vibration signal recorded from a joint during movement (articulation) of the joint.  Normal joint surfaces are smooth and produce little or no sound.  Joint affected by osteoarthiritis and other degnereative diseases may have suffered cartilage loss and produce grinding sounds.  The VAG is complex signal and difficult to analyze.


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