Action potentials of single motor units in normal muscle

Gasteiger, Edgar L.

doi:10.1016/0013-4694(55)90064-x

Cited by 66 publications

(10 citation statements)

References 42 publications

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“…This stimulus pattern is similar to the firing pattern that results from rectangular-shaped intracellular stimulation. This similarity, together with previous findings of brief duration first interspike intervals during human motor unit discharge (Norris and Gasteiger, 1955) led the authors to conclude that " . .…”

Section: Spike Frequency Adaptationsupporting

confidence: 66%

Beginning at the end: Repetitive firing properties in the final common pathway

Brownstone

2006

Progress in Neurobiology

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Since the early 20th century, it has been recognized that motoneurons must fire repetitive trains of action potentials to produce muscle contraction. In 1932, Sir John Eccles, together with Hebbel Hoff, found that action potential spike trains in motor axons were produced by "rhythmic centres", which were within the motoneurons themselves. Two decades later, Eccles attended a Cold Spring Harbor Symposium in NY, USA entitled "The Neuron". Two of the many notable presentations at this symposium were juxtaposed: one by Eccles from the University of Otago, Dunedin, NZL, and the other by J. Walter Woodbury and Harry Patton from the University of Washington, Seattle, USA. Both presentations included data obtained using sharp microelectrodes to study the intracellularly recorded potentials of cat motoneurons. In this review, I discuss some of the events leading up to and surrounding this jointly accomplished advance and proceed to discussion of subsequent studies over 5+ decades that have made use of intracellular recordings from motoneurons to study their repetitive firing behavior. This begins with early descriptions of primary and secondary range firing, and continues to the discovery of dendritic persistent inward currents and their relation to plateau potentials, synaptic amplification, and motoneuronal firing. Following a brief description of the possible mechanisms underlying spike frequency adaptation, I discuss the modulation of repetitive firing properties during various motor behaviors. It has become increasingly clear that the central nervous system has exquisite control of the repetitive firing of motoneurons. Eccles' work laid the foundation for the present-day study of these processes.

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Section: Spike Frequency Adaptationsupporting

confidence: 66%

Beginning at the end: Repetitive firing properties in the final common pathway

Brownstone

2006

Progress in Neurobiology

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“…In that case about 20o of the two to nine fibers within the pick-up range of the bipolar perpendicular electrode belong to the same motor unit. This illustrates that only in some instances it was possible to record from single motor units at maximal effort as reported by Bigland and Lippold [1], Norris and Gasteiger [2] and Hannerz [5].…”

Section: Selectivitymentioning

confidence: 58%

Recording from a Single Motor Unit During Strong Effort

Andreassen

Rosenfalck

1978

IEEE Trans. Biomed. Eng.

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Abstract-During strong voluntary effort it is rarely possible to identify the action potentials from single motor units. In large muscles the most selective recordings are obtained with bipolar wire electrodes. To elucidate this experimental finding we have calculated the extracellular field around a single muscle fiber from an intracellular muscle action potential. This model showed that the selectivity of a bipolar electrode is high provided: i) the diameter of the recording surfaces is less than half the diameter of the muscle fibers;ii) the center distance between the recording surfaces is of the same order or smaller than the diameter of the muscle fibers, and when iii) the center-line between the recording surfaces is oriented perpendicular to the direction of the muscle fibers.A bipolar electrode with these properties will give a maximal attenuation of the field from distant muscle fibers and only two to nine fibers close to the electrode contribute to the recording.Action potentials were recorded from the anterior tibial muscle of normal subjects with a trifilar cut end electrode and a bifilar side hole electrode. The recording surfaces of the side hole electrode can be positioned close to active muscle fibers by gently pulling the electrode at either side of the muscle.The recording surfaces should not be smaller than 25 Jim. Otherwise the impedances of the recording surfaces are so large that the capacitance between wire and muscle tissue degrades the selectivity of the electrode. Improving selectivity by high-pass filtering was avoided. Narrowing the frequency band made action potentials from different motor units appear similar in shape, thereby making identification more difficult. The amplitudes and the power spectra of action potentials recorded with these electrodes were in accordance with the model and no more than one to three motor units were present up to 60% of maximal effort.

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“…Indeed, the rate coding found during voluntary contractions seems well suited to use nearly the whole range of forces which the muscle can produce. The higher firing rates sometimes observed in other limb muscles (Adrian & Bronk, 1929;Lindley, 1935;Norris & Gasteiger, 1955;Marsden, Meadows & Merton, 1971) would add little to the steady force generated by this muscle.…”

Section: Discussionmentioning

confidence: 99%

Changes in firing rate of human motor units during linearly changing voluntary contractions

Milner-Brown¹,

Stein²,

Yemm³

1973

The Journal of Physiology

471

193

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SUMMARY1. Human subjects generated approximately linearly increasing or decreasing voluntary, isometric contractions using the first dorsal interosseus muscle of the hand.2. Single motor units began firing at 8-4+ 13 impulses/sec (mean + S.D. of an observation) and increased their firing rate 1*4 + 0-6 impulses/ sec for each change of 100 g in voluntary force. These values were independent of the threshold force for recruiting motor units.3. At intermediate rates of increasing and decreasing voluntary force (one complete cycle every 10 sec) the firing rate of single motor units varied linearly with force over the entire range of forces studied. However, during slow increases in voluntary force, the firing rate tended to reach a plateau, while during rapid increases an initial train of impulses at a roughly constant rate was observed.4. The relative importance of recruitment and increased firing rate, as mechanisms for increasing the force of voluntary contraction, was determined. Only at low levels of force is recuitment the major mechanism. Increased firing rate becomes the more important mechanism at intermediate force levels and contributes the large majority of force if the entire physiological range is considered.

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Action potentials of single motor units in normal muscle

Cited by 66 publications

References 42 publications

Beginning at the end: Repetitive firing properties in the final common pathway

Beginning at the end: Repetitive firing properties in the final common pathway

Recording from a Single Motor Unit During Strong Effort

Changes in firing rate of human motor units during linearly changing voluntary contractions

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