Distinguishing intrinsic from extrinsic factors underlying firing rate saturation in human motor units

Distinguishing intrinsic from extrinsic factors underlying firing rate saturation in human motor units.

During voluntary contraction, firing rates of individual motor units (MUs) increase modestly over a narrow force range beyond which little additional increase in firing rate is seen. Such saturation of MU discharge may be a consequence of extrinsic factors that limit net synaptic excitation acting on motor neurons (MNs) or may be due to intrinsic properties of the MNs. Two sets of experiments i...

Distinguishing Intrinsic from Extrinsic Factors 4 Underlying Firing Rate

Firing rate interactions among human orbicularis oris motor units.

Groups of human motor units from the same muscle exhibit joint fluctuations in firing rate during voluntary muscle contraction. In an effort to determine whether similar behavior would be observed in a muscle lacking muscle spindles, motor unit firing behavior was examined in the human orbicularis oris inferior (OOI) during mild voluntary effort. Motor unit activity was recorded with a quadrifi...

Sleep/wake firing patterns of human genioglossus motor units.

Although studies of the principal tongue protrudor muscle genioglossus (GG) suggest that whole muscle GG electromyographic (EMG) activities are preserved in nonrapid eye movement (NREM) sleep, it is unclear what influence sleep exerts on individual GG motor unit (MU) activities. We characterized the firing patterns of human GG MUs in wakefulness and NREM sleep with the aim of determining 1) whe...

Cell intrinsic & extrinsic factors in cervical carcinogenesis.

Human papillomavirus (HPV) infection is a common sexually transmitted infection which a majority of infected women are able to clear by mounting an effective immune response. Individuals with a suboptimal immune response may be at increased risk of persistent HPV infection leading to sequelae of various grades of dysplasias and / or associated malignancy. Both cell intrinsic and extrinsic pheno...