| Autor: |
Kristan, William, Stent, Gunther, Ort, Carol |
| Zdroj: |
Journal of Comparative Physiology; Oct1974, Vol. 94 Issue 2, p97-119, 23p |
| Abstrakt: |
Leeches swim by undulating their extended and flattened body in the dorsoventral direction, to form a wave that travels backwards along the animal. The troughs and crests of this body wave are produced by a metachronal rhythm of antiphasic contractions of the dorsal and ventral longitudinal musculature of the body wall of successive segments. Cinematographic records of swimming leeches show that over a range of cycle periods from 390 to 1100 msec the animal maintains one full wave along the length of its body. This constant wave form is achieved by compensating for the increase in the cycle period by an increase in the intersegmental travel time of the wave from 19 to 77 msec per segment. Direct muscle tension measurements of the segmental body wall during the swimming movement of a restrained, brainless and partially denervated leech lead to values for the dynamic parameters of the body wave which are in agreement with those abstracted from cinematographic records. In order to study the neuronal control of the swimming movement, a semi-intact leech preparation was developed. This preparation carries out movements that are clearly vestiges of the swimming rhythm while allowing the taking of electrophysiological records from exposed and immobilized parts of its peripheral and central nervous systems. The records reveal a nerve cell activity rhythm whose period matches that of the swimming rhythm. The swimming rhythm and its body wave must be generated by a system of distributed, phase-locked segmental oscillators that cause an antiphasic activity of the motor neurons innervating the segmental dorsal and ventral longitudinal muscles. The cycle of these oscillators can be inferred to consist of a variable time sector whose changes in length are responsible for changes in the cycle period, and of a constant time sector whose length is independent of the cycle period. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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