Numbers and central projections of crab second maxilla motor Neurones

Pilkington, J. B.; Macfarlane, D.

doi:10.1017/s0025315400041230

Cited by 16 publications

(7 citation statements)

References 22 publications

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“…Our histological and physiological observations confirm previous reports (Pasztor 1968(Pasztor , 1969Young 1975;Pilkington and MacFarlane 1978;Moody-Corbett and Pasztor 1980) that the levator nerve which carries the motor neurons to the SG levator and D2a depressor muscles also contains virtually all of the small diameter afferent axons to the SG. The LNa branch carries all of the levator motor neurons and very few small diameter afferent axons.…”

Section: The Sg Nervessupporting

confidence: 91%

“…The LNb branch carries in order of decreasing size, the three giant axons innervating the oval organ proprioceptor, the two D2a motor neurons and the majority of small diameter afferent axons. The count of axons in the size class thought to represent motor neurons (greater or equal to 6 lam diam) agrees reasonably well with estimates of the numbers of motor neurons based on size classes of excitatory junction potentials recorded from the SG muscles (Pilkington and MacFarlane 1978;Moody-Corbett and Pasztor 1980). All of the afferent neurons except the three OOAs have their somata located at the periphery in the SG (Pasztor 1969).…”

Section: The Sg Nervessupporting

confidence: 74%

“…The distribution of axons in the SG nerves has been documented by electrophysiological techniques (Pasztor 1968(Pasztor , 1969Young 1975;Pilkington and MacFarlane 1978), but no histology has been published. From these studies it is estimated that the SG muscles receive from 35 to 39 motor neurons.…”

Section: Histology Of Sg Nervesmentioning

confidence: 99%

“…One of the branches of LN, LNa, carries all of the levator muscle motor neurons (16-18) and a few small diameter afferent axons. In the LNb branch the three largest axons are the oval organ afferents (OOA), the two next largest are the depressor D2a motor neurons, about 8 more axons can be considered to be motor neurons and the large (Pilkington and MacFarlane 1978). The other second maxilla nerve divides close to the thoracic ganglion into the depressor nerve (DN) which innervates all of the SG depressor muscles, except D2a, and a branch to the endites (SN).…”

Section: Histology Of Sg Nervesmentioning

confidence: 99%

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Effects of scaphognathite nerve stimulation on the acutely deafferented crab ventilatory central pattern generator

Wilkens

DiCaprio

1994

J Comp Physiol A

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Sensory axons from crab (Carcinus maenas)scaphognathites enter the thoracic ganglion primarily via the LNb branch of the levator nerve. The LNa branch of the levator nerve and the depressor nerve each contain relatively few sensory axons.2. Acutely deafferented ventilatory central pattern generators show a free running burst rate which is lower than that observed in intact crabs. Electrical stimulation of the levator nerve, or of its LNb branch, increases the burst rate in a frequency dependent manner. Stimulation at high enough intensity to recruit afferents will restart a paused motor rhythm. Stimulation of the levator nerve with short pulse trains phase resets and can entrain the rhythm.3. In addition to increasing the burst rate, LNb stimulation also causes a progressive elimination of motor neurons from the bursts as the stimulating frequency increases, probably due to depolarization of the 3 oval organ 'giant' afferent axons in this branch. Intracellular depolarization of single oval organ afferents will also inhibit some motor neurons as well as slow or stop the rhythm.4. Continuous stimulation of the depressor nerve does not affect the ganglionic burst rate and this nerve contains only a few small diameter afferent axons; however, brief trains of stimuli can reset the rhythm in a phase-dependent manner.

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Section: The Sg Nervessupporting

confidence: 91%

Section: The Sg Nervessupporting

confidence: 74%

Section: Histology Of Sg Nervesmentioning

confidence: 99%

Section: Histology Of Sg Nervesmentioning

confidence: 99%

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Effects of scaphognathite nerve stimulation on the acutely deafferented crab ventilatory central pattern generator

Wilkens

DiCaprio

1994

J Comp Physiol A

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“…The SC muscles are innervated by two to four excitatory (and no inhibitory) axons and possess highly facilitating synapses (Moody-Corbett & Pasztor, 1980;Pilkington & MacFarlane, 1978). It has been proposed that the force generated by the SC muscles is varied mainly through changes in the firing frequencies and axonal recruitment of the motor neurones (Moody-Corbett & Pasztor, 1980).…”

Section: Introductionmentioning

confidence: 99%

Analysis Of The Scaphognathite Ventilatory Pump in the Shore Crab Carcinus Maenas III. Neuromuscular Mechanisms

Mercier

Wilkens

1984

Journal of Experimental Biology

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The motor output pattern to one of the ventilatory muscles of the scaphognathite (SC) in the shore crab, Carcinus maenas, was analysed from extracellular nerve recordings. During ‘forward mode’ bursting, an increase in the burst rate of L2b motor neurones is accompanied by an increase in the average intraburst firing frequency. The number of action potentials per burst, although variable, does not change consistently as a function of burst rate. The influence of individual aspects of the motor pattern on isotonic contractions of muscle L2b was examined. Increasing the intraburst frequency leads to greater contraction and work output, and allows the muscle to lift heavier loads. This effect is correlated with an increase in the level of postsynaptic depolarization, due, at least in part, to greater summation of EPSPs. Increasing the burst rate alone also enhances muscle contraction and work, and results in greater depolarization. This latter effect appears to involve an accumulation of short-term facilitation, which becomes more acute as the time interval between the bursts is progressively shortened. In addition, contraction and depolarization are augmented by increasing the number of impulses per burst or the number of axons recruited. These observations indicate some aspects of the motor output pattern which are appropriately modified to accommodate the changes in force and work demands which accompany a change in gill ventilation rate.

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Nonspiking interneurons in the ventilatory central pattern generator of the shore crab, Carcinus maenas

DiCaprio¹

1989

J of Comparative Neurology

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Eight nonspiking interneurons were identified that are elements of the central pattern generator controlling ventilation in the shore crab, Carcinus maenas. Intracellular recordings from these neurons in an isolated ganglion preparation revealed that these cells exhibit large amplitude oscillations in their membrane potentials, which are in-phase with the ventilatory motor pattern. These oscillations are present during the expression of the two distinct ventilatory motor output patterns corresponding to forward and reversed ventilation, and the oscillations stopped during pauses in the ventilatory rhythm. Injection of intracellular current pulses into these interneurons caused a resetting of the ongoing ventilatory rhythm, indicating that these cells are part of the ventilatory central pattern generator. The structure of each interneuron was determined by the intracellular injection of Lucifer Yellow dye. These neurons have a large diameter main neurite ranging from 10 to 20 microns in diameter with very restricted primary and secondary branching from the main neurite. All of the interneurons are restricted to a single hemiganglion and perturbation of these cells with intracellular current pulses only affect the motor output of the hemiganglion containing the interneuron. These eight nonspiking interneurons appear to be the primary components of the central pattern generator underlying ventilation in the crab.

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Numbers and central projections of crab second maxilla motor Neurones

Abstract: The second maxilla is innervated typically by 35 motor neurones in Nectocarcinus antarcticus and about 39 in Cancer novaezelandiae. Muscles are multiply innervated. Within one species variations in the number of motor neurones innervating any muscle do occur but are not common.

Cited by 16 publications

References 22 publications

Effects of scaphognathite nerve stimulation on the acutely deafferented crab ventilatory central pattern generator

Effects of scaphognathite nerve stimulation on the acutely deafferented crab ventilatory central pattern generator

Analysis Of The Scaphognathite Ventilatory Pump in the Shore Crab Carcinus Maenas III. Neuromuscular Mechanisms

Nonspiking interneurons in the ventilatory central pattern generator of the shore crab, Carcinus maenas

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