Biomaterial Database

Discharge variability and physiological properties of human masseter motor units. 1991

M A Nordstrom, and T S Miles

Department of Physiology, University of Adelaide, Australia.

Intramuscular electrodes were used to study discharge variability in motor units of human masseter whose physiological properties were determined using spike-triggered averaging. Subjects voluntarily controlled the mean firing rate of a selected motor unit at 10 Hz for 15 min of continuous activation. Discharge variability was assessed at the beginning and end of this period. In 81% of units, the discharge variability at a mean interspike interval (ISI) of 100 ms increased after 15 min of continuous activity. There was a wide range of discharge variability within the population of masseter units studied, but no significant correlations were found between initial discharge variability and recruitment threshold, twitch tension or time-to-peak tension (TTP). There was, however, a significant correlation between motor unit fatigability and its initial discharge variability. This represents a link between the motoneuron and the functional properties of the muscle fibers in innervates.

UI	MeSH Term	Description	Entries
D008406	Masseter Muscle	A masticatory muscle whose action is closing the jaws.	Masseter Muscles,Muscle, Masseter,Muscles, Masseter
D009046	Motor Neurons	Neurons which activate MUSCLE CELLS.	Neurons, Motor,Alpha Motorneurons,Motoneurons,Motor Neurons, Alpha,Neurons, Alpha Motor,Alpha Motor Neuron,Alpha Motor Neurons,Alpha Motorneuron,Motoneuron,Motor Neuron,Motor Neuron, Alpha,Motorneuron, Alpha,Motorneurons, Alpha,Neuron, Alpha Motor,Neuron, Motor
D009119	Muscle Contraction	A process leading to shortening and/or development of tension in muscle tissue. Muscle contraction occurs by a sliding filament mechanism whereby actin filaments slide inward among the myosin filaments.	Inotropism,Muscular Contraction,Contraction, Muscle,Contraction, Muscular,Contractions, Muscle,Contractions, Muscular,Inotropisms,Muscle Contractions,Muscular Contractions
D011999	Recruitment, Neurophysiological	The spread of response if stimulation is prolonged. (Campbell's Psychiatric Dictionary, 8th ed.)	Recruitment, Motor Unit,Motor Unit Recruitment,Neurophysiological Recruitment
D004056	Differential Threshold	The smallest difference which can be discriminated between two stimuli or one which is barely above the threshold.	Difference Limen,Just-Noticeable Difference,Weber-Fechner Law,Difference Limens,Difference, Just-Noticeable,Differences, Just-Noticeable,Differential Thresholds,Just Noticeable Difference,Just-Noticeable Differences,Law, Weber-Fechner,Limen, Difference,Limens, Difference,Threshold, Differential,Thresholds, Differential,Weber Fechner Law
D004594	Electrophysiology	The study of the generation and behavior of electrical charges in living organisms particularly the nervous system and the effects of electricity on living organisms.
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000293	Adolescent	A person 13 to 18 years of age.	Adolescence,Youth,Adolescents,Adolescents, Female,Adolescents, Male,Teenagers,Teens,Adolescent, Female,Adolescent, Male,Female Adolescent,Female Adolescents,Male Adolescent,Male Adolescents,Teen,Teenager,Youths
D000328	Adult	A person having attained full growth or maturity. Adults are of 19 through 44 years of age. For a person between 19 and 24 years of age, YOUNG ADULT is available.	Adults