Biopotentials

High concentrations (from 10"5 to 10"1 M) either quickly destroy the mechanism of biopotential generation or block the transmission in the synaptic formations, thus sharply decreasing the electrical activity of giant axons. However, the concentrations ranging from 10"4 to 10" 3 M are far from physiological and this makes the interpretation of this effect rather difficult. 

The genomic DNA is of necessity without design. All of the information contained within the strand in form of sequence variability comes to light through the code. One could state that the nearly limitless potential information hidden in the tons of nucleic acid of the DNA or RNA type, regardless of which code would be adapted, would inevitably lead to all the life forms on earth. The total variety of life forms on a particular planet under proper biogenesis conditions becomes a function of the total amount and variability of nucleic acids available. That gives us a biopotential theorem worthy of the new millennium. 

Matsuo T, Wise KD (1974) An integrated field-effect electrode for biopotential recording. 

Selvin, J. and Lipton, A. P. (2004). Biopotentials of Ulva fasciata and Hypnea musciformis collected from the peninsular coast of India. /. Mar. Sci. Technol. 12(1), 1-6. 

Wireless sensors capable of measuring biopotentials, angle, position, pressure, temperature, and permanent magnet fields. 

Biopotential Sensing, Data Display, and Data Analysis... 

FIGURE 34.7 Biopotential sensing module, oscilloscope display mode. 

FIGURE 34.8 Data analysis with the BPB biopotential sensing module, (a) Counting pulses above threshold line, (b) Rectify and integrate neural signal. 

The different functions of the BPB (as a stimulator, biopotential signal sensor, goniometry sensor, and pressure or temperature sensor) and the availability of multiple BPBs in one patient (up to 850 BPBs) gives the cUnidan many opportunities to restore neurological function, espedaUy in poststroke syndrome, spinal cord injury, cerebral palsy, multiple sclerosis, traumatic brain injury, and for limb sensing in amputees to control fitted prostheses. 

For Amputee Patients (Figure 34.14) BPBs, working as biopotential sensors, would be inserted in the stump to pick up motor nerve signals, which can be used to control movement of the artificial limb flexible components . 

Type of end use — this may deal with transmission of information (biopotentials, temperature, pressure, blood flow rate), energy (electrical stimulation, power for heart-assist devices), transfer of matter (cannula for blood), and load (attachment of a prosthesis) ... 

An LC circuit was also coupled with a varactor for in vivo biopotential monitoring. Electrodes sense the variation in biopotential, which was used to alter the bias voltage of the varactor, thus causing its capacitance to change. The alteration in capacitance caused a variation in the LC resonant frequency, which was reflected in the impedance of the detection coil (Rustama 2007). 

TABLE 4.1 Bioelectric Signals Sensed by Biopotential Electrodes and Their Sources... 

TABLE 4.2 Half-Cell Potentials for Materials and Reactions Encountered in Biopotential Measurement... 

FIGURE 4.1 Silver-silver electrodes for biopotential measurements (a) metallic silver with a silver chloride surface layer and (b) sintered electrode structure. The lower views show the electrodes in cross section. 

The electrical characteristics of biopotential electrodes are generally nonlinear and are a function of the current density at their surface. Thus, having the devices represented by linear models requires that they be operated at low potentials and currents. Under these idealized conditions, electrodes can be represented by an equivalent circuit of the form shown in Figure 4.2. In this circuit, Rj and Q are components... 

FIGURE 4.3 An example of biopotential electrode impedance as a function of frequency. Characteristic frequencies will be somewhat different for different electrode geometries and materials. 

Electrodes can be placed within the body for biopotential measurements. These electrodes are generally smaller than skin surface electrodes and do not require special electrolytic coupling fluid because natural body fluids serve this function. There are different designs for these internal electrodes, and only a few examples are given in the following paragraphs. Basically, these electrodes can be classified... 

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