Relation between isometric force and stimulus rate in cat's hindlimb motor units of different twitch contraction time

Simulation system of spinal cord motor nuclei and associated nerves and muscles, in a Web-based architecture

“…For simulations of a type S MN subjected to trains of pulse stimuli at rates from 2 Hz up to 40 Hz, the resulting F×f plot was a straight line (saturating at 40 gf) with a slope of 7.9%/Hz, which is within the range found in human toe extensors (Macefield et al 1996) and cat medial gastrocnemius muscle (Kernell et al 1983). The shape of the F×f relation did not follow the sigmoidal shape found in real motor units because of the simple approach used in the simulator (see Section 4).…”

“…Sigmoidal relation between force level and MU firing rate (Kernell et al 1983;Macefield et al 1996;Van Zandwijk et al 1996) 2. "Catch" property in slow-type motor units (Burke et al 1970;Otazu et al 2001) 3.…”

Prolonged activity evokes potentiation and the “sag” phenomenon in slow motor units of rat soleus

“…The prolongation of potentiated twitches noted for the studied MUs was also observed for fast as well as for slow MUs of cat gastrocnemius (Burke et al 1973). It is known that the contraction time correlates to a course of force-frequency of stimulation curve (Kernell et al 1983). Therefore, most probably as an effect of this prolongation the force-frequency curves of male and female MUs were shifted to the left, a result similar to that found for potentiated fast MUs (Celichowski and Grottel 1997).…”

Functional Properties of Motoneurons Derived from Mouse Embryonic Stem Cells

“…Steady-state firing frequencies of up to 20 Hz were detected in ES cell-derived MNs. These rates are in the appropriate range for developing MNs (Martin-Caraballo and Greer, 1999) as well as adult type slow MNs (Kernell et al, 1983). In contrast, other spinal neurons such as dorsal spinocerebellar tract neurons (cat) (Gustafsson, 1984) or unidentified ventral interneurons (turtle) (McDonagh et al, 1998) fire at much higher frequencies.…”