Observations on the discharge of flexor motoneurones

Perl, Edward R.

doi:10.1113/jphysiol.1962.sp007031

Cited by 14 publications

(11 citation statements)

References 19 publications

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“…Again, with latency as a criteria, responses following a TS volley were mediated by a polysynaptic reflex (Lloyd, 1943b;Eccles & Lundberg, 1959a;Perl, 1962). Figure 4 gives the distribution of FI for three sizes of TS volley for those cells for which such data were available.…”

Section: Resultsmentioning

confidence: 99%

“…The distribution of FI for the same motoneurones (with a few omissions) excited during a polysynaptic reflex (on the basis of latency: Lloyd, 1943a, Perl, 1962 initiated by sural volleys is shown in Fig. 3.…”

Section: Resultsmentioning

confidence: 99%

“…Many of the motoneurones discharged repetitively to single large volleys (Perl, 1962). Only the first discharge was used to calculate FI.…”

Section: Methodsmentioning

confidence: 99%

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A comparison of monosynaptic and polysynaptic reflex responses from individual flexor motoneurones

Perl¹

1962

The Journal of Physiology

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Evidence from a number of types of experiments has shown that gradation of muscular contraction is accomplished by changes both in the number of motoneurones active and in the frequency of discharge of individual motoneurones (Creed, Denny-Brown, Eccles, Liddell & Sherrington, 1932). It is also well known that different spinal reflexes have different abilities to excite fractions of the motoneurone pool supplying a particular muscle. On the other hand, there appears to be little information on one important feature of the functional organization of motoneurones particularly relevant to quantitative control of skeletal muscle contraction, namely, the degree of influence various reflex pathways have on a particular motoneurone in comparison to other motoneurones of the same pool.The present study examines the effectiveness of the monosynaptic and several polysynaptic reflex arcs in discharging individual knee flexor motoneurones. These experiments should be useful in indicating whether a given motoneurone responds equally well to different reflex pathways or whether variation in excitation throughout a particular pool is dependent upon the nature of the reflex process. Information on such a point would be valuable in helping to ascertain the manner in which different mechanisms combine to determine the participation of motoneurones in activity. For instance, it has been postulated that a significant control of motoneurone excitability is exerted via the fusimotor (gamma) effect upon the afferent limb on the monosynaptic reflex, the Group I fibres from the muscle spindle (Eldred, Granit & Merton, 1953). Fitting the motor control of the spindle into the framework of mechanisms concerned with the functional organization of motoneurones would require knowledge of how the effectiveness of the monosynaptic drive varies among members of a pool in comparison to other excitatory pathways.The motoneurones studied were taken from the pool monosynaptically excited by Group I volleys from the peripheral nerves supplying the

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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A comparison of monosynaptic and polysynaptic reflex responses from individual flexor motoneurones

Perl¹

1962

The Journal of Physiology

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“…After amplification, the activity was displayed and photographed from a two-channel oscilloscope or stored on magnetic tape using an FM analogue system. In some cases, the latencies between stimulus and response of a single unit were measured with a digital time-interval meter (Perl, 1962).…”

Section: Methodsmentioning

confidence: 99%

Background and reflex discharge of sympathetic preganglionic neurones in the spinal cat

Beacham¹,

Perl²

1964

The Journal of Physiology

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“…In flexor reflexes the d'emblee opening of the response suggests high initial frequencies and this surmise has proved to be correct (see e.g. Perl, 1962). In intracellular work on flexor motoneurones Wilson & Talbot (1964) recently noted brief initial discharges at rates as high as 400-500 impulses/sec, definitely implicating the secondary range of firing.…”

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confidence: 99%

Synaptic stimulation superimposed on motoneurones firing in the ‘secondary range’ to injected current

Granit¹,

Kernell²,

Lamarre³

1966

The Journal of Physiology

100

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SUMMARY1. This paper extends the work on the 'primary range' of firing (Granit, Kernell & Lamarre, 1966), in lumbar motoneurones to the 'secondary range'. By definition the latter begins when, with stronger currents, the linear curve relating firing rate to injected current in the primary range undergoes a fairly sudden increase of slope.2. It was shown that motoneurones firing at the higher frequencies of the secondary range were partially inactivated. Yet such firing rates were within the physiological range.3. Algebraical summation of firing rates, when present in the secondary range, implied at the same time that the synaptic amount added was diminished by comparison with what it had been within the primary range.4. Superimposed synaptic excitatory stimuli did not (as in the 'primary range') regularly add their effect algebraically on to the rate of firing achieved by injected currents alone. More commonly the synaptic effect of the constant input underwent a progressive increase throughout the secondary range.5. Superimposed inhibitory stimuli regularly reduced the slope constant as determined by trans-membrane current alone and, by counteracting inactivation, made the motoneurone approach the mode of firing characteristic of the 'primary range'.6. The latter finding emphasizes the significance of analysing firing motoneurones with the aid of 'slope constants ' and provides inhibition with a new role in the integrative behaviour of motoneurones, as considered in the Discussion.

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Observations on the discharge of flexor motoneurones

Abstract: Much of the current knowledge of circumstances attending the discharge of a specific motoneurone is based upon studies either dealing with cells innervating extensor muscles or done on preparations depressed by anaesthesia (Brock,

Cited by 14 publications

References 19 publications

A comparison of monosynaptic and polysynaptic reflex responses from individual flexor motoneurones

A comparison of monosynaptic and polysynaptic reflex responses from individual flexor motoneurones

Background and reflex discharge of sympathetic preganglionic neurones in the spinal cat

Synaptic stimulation superimposed on motoneurones firing in the ‘secondary range’ to injected current

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