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3 Fundamentals of the Formation of Biosignals
Axon
Myelin steath
0
RP
Time
U/mV
0
U/mV
a
L2
0
RP
0
a
U/mV
U/mV
Time
+
- -
+
+
- -
+
+
- -
+
+
- -
+
-
++
-
-
++
-
-
++
-
-
++
-
Fig. 3.11: Propagation of the action potential in saltatory excitatory conduction. The action poten-
tial propagates by regeneration at the node of Ranvier abruptly with a nerve conduction velocity of
10, . . . , 50 m/s; the partial illustrations on the left and right refer to different times.
not a hindrance to function. Nerve diseases such as multiple sclerosis result from the
dissolution of the myelin sheath, i.e. from the body’s autoimmune reaction to destroy
its own cells; on the other hand, in diseases such as amyloidosis or Alzheimer’s dis-
ease, misfolded proteins accumulate in the node of Ranvier, which damage the erratic
conduction.
The propagation of the action potential along a saltatory excitation conduction
is shown in Figure 3.11. Depolarisation here occurs abruptly from node of Ranvier to
node of Ranvier, resulting in propagation velocities between 10 and 50 m/s. The de-
polarisation occurs practically instantaneously due to the propagation of the electric
field across the sections of the myelin sheath, i.e. the potential in the adjacent node
of Ranvier rises faster than in the area of the myelin sheath due to the much lower
electric capacity there and thus exceeds the membrane threshold, so to speak, before
the action potential reaches the node of Ranvier.
3.2 Electrophysiology of the Heart
The transfer of electrophysiological processes to the level of the organism is exem-
plified in this important section on the heart physiology using biosignal processing.
However, as explained in section 3.3, the knowledge gained in this process can easily
be used for other parts of the body such as muscle and nerve activity. The Respective
applications are explained in more detail in chapter 6 using a practical example.