Variability of the twitch responses to indyvidual stimuli at random stimulation patterns of fast and slow motor units in rat medial gastrocnemius

• Autorzy: Celichowski J. , Raikova R. , Krutki P.
• Języki publikacji: EN

Abstrakty

EN

The unfused tetani evoked by train of stimuli at variable interpulse intervals (IPIs) of fast fatigable (FF), fast resistant (FR) and slow (S) motor units (MUs) were recorded and then decomposed into trains of twitch-shape responses to successive stimuli. The mean stimulation frequency was matched for each MU to evoke tetani of a similar fusion degree (lower for slow MUs, higher for fast MUs), whereas the variability range of IPIs was 50 – 150% of the mean IPI value for a given MU. The decomposition was done using an experimentally verified mathematical algorithm, described previously. Ten MUs of each type were analyzed. For each MU the twitch force, the contraction time and the force-time area for the single twitch recording were calculated and compared to both, the strongest and the weakest of the responses to successive stimuli. For each of studied MUs considerable variability of twitch parameters for responses to successive stimuli was observed, although the largest range of variability characterized slow MUs. In general, the decomposed twitch responses were stronger and had longer duration than the single twitches, although especially for 9 FF and to a smaller degree for 6 FR MUs the smallest decomposed responses were weaker but not faster than the single twitches of these MUs. The mean value of a ratio of the strongest decomposed twitch force to the single twitch force amounted to 2.4, 1.8 and 5.5 for FF, FR and S MUs, respectively. The ratio of the strongest decomposed twitch force-time area to the single twitch force-time area amounted to 1.8, 2.2 and 9.5 for FF, FR and S MUs, respectively. Analogically calculated ratio for the contraction time amounted to 1.5, 1.5 and 2.2 for FF, FR and S MUs, respectively. In conclusion, the results evidence that during voluntary activity of muscles successive action potentials generated especially by motoneurons of slow MUs have considerable variability in relation to evoked contractile responses of muscle fibers.

• Wydawca: -
• Czasopismo: Acta Neurobiologiae Experimentalis
• Rocznik: 2011
• Tom: 71
• Numer: S
• Opis fizyczny: p.81

Twórcy

autor

Celichowski J.

• Department of Neurobiology, University School of Physical Education in Poznan, Poznan, Poland

autor

Raikova R.

• Centre of Biomedical Engineering, Bulgarian Academy of Sciences in Sofia, Sofia, Bulgaria

autor

Krutki P.

• Department of Neurobiology, University School of Physical Education in Poznan, Poznan, Poland

Uwagi

Rekord w opracowaniu