
354 Forensic Engineering Fundamentals
Based on the resistance and capacitance of cell membranes, the current according to
the Blair curve is expressed as
It
b
t
()=
−
τ
(11.25)
where τ is the membrane time constant. e time constant for dierent human tissue is
shown in Table 11.14.
All excitable cells are surrounded by an ion-permeable membrane, which results in a high
concentration of potassium (K
+
) ions in the cell and a high concentration of sodium (Na
+
) ions
outside the cell. e net eect is a transmembrane potential as shown in Figure 11.5.
Dalziel reported the rst studies on the threshold for perception to sinusoidal current.
Figure 11.6 rep ...