Examples of Biomedical Signals 2 nd practice Medical

Examples of Biomedical Signals 2 nd practice Medical Informatics Biomedical Signal Processing TAMUS, Zoltán Ádám zoltanadam_tamus@yahoo. com

Examples of Biomedical Signals �Action potential �Electroneurogram (ENG) �Electromyogram (EMG) �Electrocardiogram (ECG) �Electroencephalogram (EEG) �Electrogastrogram (EGG) �Phonocardiogram (PCG) �Carotid Pulse (CP) �Vibromyogram (VMG) �Vibroarthogram (VAG)

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

The Action Potential 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 50 -100 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 m. V

The Action Potential �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 m. V

The Action Potential 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 150 -300 ms

$The Action Potential � All-or-none phenomenon � Absolute refractory period: 1 ms in nerve$

The Action Potential � All-or-none phenomenon � Absolute refractory period: 1 ms in nerve cells � Relative refractory period: several ms in nerve cells

The Action Potential

Electroneurogram (ENG) � 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-Ag. Cl electrodes at the surface of the body. � In order to minimize muscle contraction strong but short stimulus is applied (100 V amplitude, 100 -300 μs). � ENGs have amplitudes of the order of 10 μV.

Electroneurogram (ENG) Wirst BElbow - below the elbow AElbow – above the elbow

Electroneurogram (ENG) Typical values of propagation rate or nerve conduction velocity are: • 45 -70 m/s in nerve fibers • 0. 2 -0. 4 m/s in heart muscle • 0. 03 -0. 05 m/s in time delay fibers between the atria and ventricles. Neural diseases may cause a decrease in conduction velocity.

Electromyogram (EMG) Motor units Single Motor Unit Action Potential (SMUAP)

Electromyogram (EMG) Normal SMUAPs are usually biphasic or triphasic 3 -15 ms in duration, 100 -300 μV in amplitude, 6 -30 Hz in frequency range

Electroencephalogram (EEG) The 10 -20 system of electrode placement for EEG recording.

Electroencephalogram (EEG) 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

Electroencephalogram (EEG) � a: delta, b: theta, c: alpha, d: beta, e: blocking of alpha rhythm by eye opening, f: marker 50 μV, 1 sec

Electrogastrogram (EGG) 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

Carotid Pulse (CP) � 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

Vibromyogram (VMG) Direct mechanical manifestation of contraction of a skeletal muscle. Accompanies the EMG Recorded by contact microphones or accelerometers placed on the muscle surface.

Vibroarthogram (VAG) � 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.