Figure 1.
Study of pulse wave propagation in Lumbriculus variegatus.
(A) Cross-sectional view of a Lumbriculus segment with intestine (I), ventral nerve chord (VNC), ventral (VBV) and dorsal blood vessel (DBV). The latter are partially connected by lateral vessels (LV). (B) A blackworm is aspirated into a buffer-filled glass capillary (WIC) and subsequently submersed in a temperature-controlled petri dish (TEMP). (C) Top view of WIC with the DBV (light-gray structure in the center) and a propagating pulse wave (arrow).
Figure 2.
Variation of pulse wave velocity with environmental temperature.
Data was normalized to each individual worm’s pulse propagation velocity at 9.2±0.3°C (average: 0.19±0.05 mm s−1). The black envelopes are guides to the eye. Each data point represents the average of at least 36 measurements. Number of worms studied = 29.
Figure 3.
Variation of pulse frequency with environmental temperature.
Data was normalized to each individual worm’s pulse frequency at 9.3±0.7°C (average: 4.4±0.8 beats min−1). The black envelopes are guides to the eye. Each data point represents the average of six measurements. Number of worms studied = 68.
Figure 4.
Reversible heat-block of pulse propagation.
Heating of a worm above a critical temperature (average threshold temperature: 37.2±2.7°C; min: 33°C, max: 43°C; number of worms studied = 17) led to cessation of blood vessel pulsations. Regular contractions reappeared upon quick cooling. Illustrated is a typical temperature-frequency response as obtained from a single worm. Dashed lines are guides to the eye.
Figure 5.
Thermodynamic approach: Experiments, predictions and comparisons.
Based on experimentally obtained temperature-pulse velocity profiles c (left column), temperature-dependent compressibilities κ and relaxation times τ (middle column) were calculated for blood vessel pulsations in worms (A), action potentials in human nerves (B; data taken from Fig. 1 in [17]) and waves in gel rods (C; data taken from Fig. 3 and 4 in [16]). Comparison of predicted relaxation times τ and frequencies ν with their experimentally obtained counterparts (right column). Experimental data are always plotted as open triangles connected by broken lines while predictions are plotted as filled circles connected by solid lines.