Coxal Muscle Receptors in the Crab: The Receptor Potentials of S and T Fibres in Response to Ramp Stretches

1971 ◽  
Vol 55 (3) ◽  
pp. 813-832
Author(s):  
B. M. H. BUSH ◽  
ALAN ROBERTS
Keyword(s):  
Motor Nerve ◽  
Large Diameter ◽  
Muscle Fibres ◽  
Dynamic Component ◽  
Static Responses ◽  
Basal Joint ◽  
Muscle Receptors ◽  
Shore Crabs ◽  
Static Nature ◽  
Receptor Muscle

1. Intracellular and extracellular recordings from the two large-diameter S and T sensory fibres of the posterior thoracico-coxal muscle receptor in shore crabs confirm the graded, dynamic-static nature of the receptor potentials evoked by stretching the receptor muscle, and the lack of afferent impulses. 2. Slow ramp-function stretches evoke receptor potentials with characteristic shapes, which differ between the two fibres in several respects: (i) The dynamic component in the S fibre resembles an algebraic sum of length and velocity responses and a variable initial ‘acceleration’ (?) transient, while in the T fibre it commonly declines (‘adapts’) during stretching, especially at greater velocities and starting lengths. (ii) On release of stretch the S fibre usually exhibits a ‘negative velocity response’, but the T fibre repolarizes rapidly often with a slight hyperpolarization. (iii) The dynamic response of the T fibre is generally greater than that of the S fibre, and increases more steeply and approximately logarithmically with stretch velocity over a 10- to 50-fold range. (iv) The ‘static response’ or degree of depolarization increases fairly linearly with receptor length in the S fibre but very non-linearly in the T fibre. (v) The T fibre displays pronounced hysteresis in its dynamic and static responses at increasing and decreasing lengths, but the S fibre shows little hysteresis. (vi) The T fibre but not the S fibre commonly shows small rapid oscillations or ‘noise’ superimposed upon strongly depolarized ‘static’ potentials. (vii) The S and T responses may be affected reciprocally by some forms of receptor muscle contraction. 3. Graded receptor potentials evoked in the ‘D’ fibre by stretching the non-muscular depressor-receptor strand of the coxo-basal joint show little hysteresis. 4. Receptor muscle fibres respond to motor nerve stimulation or spontaneous motor impulses from the thoracic ganglion with slow, facilitating and summating excitatory junctional potentials. 5. The mechanisms underlying the differences between S and T responses, and their functional significance to the animal, are discussed, and comparisons are drawn with other muscle receptors.

scholarly journals Comparison of Dynamic Characteristics between Small and Super-Large Diameter Cross-River Twin Tunnels under Train Vibration

2021 ◽  
Vol 11 (16) ◽  
pp. 7577
Author(s):  
Lin Wu ◽  
Xiedong Zhang ◽  
Wei Wang ◽  
Xiancong Meng ◽  
Hong Guo
Keyword(s):  
Dynamic Characteristics ◽  
Large Diameter ◽  
Horizontal Displacement ◽  
Element Model ◽  
Vertical Displacement ◽  
Decisive Factor ◽  
Cross River ◽  
Static Responses ◽  
Train Vibration ◽  
Twin Tunnels

Train vibration from closely aligned adjacent tunnels could cause safety concerns, especially given the soaring size of the tunnel diameter. This paper established a two-dimensional discrete element model (DEM) of small (d = 6.2 m) and super-large (D = 15.2 m) diameter cross-river twin tunnels and discussed the dynamic characteristics of adjacent tunnels during the vibration of a train that runs through the tunnel at a speed of 120 km/h. Results in the D tunnel showed that the horizontal walls have the same horizontal displacement (DH) and the vertical walls have the same vertical displacement (DV). The stress state of the surroundings of the D tunnel is the decisive factor for DH, and the distance from the vibration point to the measurement point is the decisive factor for DV. Results in the comparison of the d and D tunnels showed that the D tunnel is more stable than the d tunnel with respect to two aspects: the time the tunnel reaches the equilibrium state and the vibration amplitude of the structure’s dynamic and static responses. The dynamic characteristic of the d and D tunnel is significantly different. This research is expected to guide the design and construction of large diameter twin tunnels.

The Early Development of Muscle Spindles in the Rat

1973 ◽  
Vol 12 (1) ◽  
pp. 175-195
Author(s):  
ALICE MILBURN
Keyword(s):  
Close Association ◽  
Large Diameter ◽  
Muscle Spindles ◽  
Muscle Fibres ◽  
Intrafusal Muscle ◽  
Intrafusal Fibres ◽  
Fusimotor Innervation ◽  
Nuclear Chain ◽  
Intramuscular Nerve

The morphogenesis of muscle spindles in rat lower hind-limb muscles has been investigated using the electron microscope. The earliest detectable spindles are seen in the 19.5-day foetus and consist of a single myotube bearing simple nerve terminals of the large primary afferent axon from nearby unmyelinated intramuscular nerve trunks. The capsule forms by an extension of the perineural epithelium of the supplying nerve fasciculus, and is confined initially to the innervated zone. Myonuclei accumulate in this region, so that the first intrafusal muscle fibre to develop is a nuclear-bag fibre. Myoblasts, present within the capsule of the spindle throughout its development, fuse to form a smaller less-differentiated myotube by the 20-day foetal stage. This new myotube matures by close association with the initial fibre, and by birth (21-22 days gestation) has formed the smaller, intermediate bag fibre, that has been identified histochemically and ultrastructurally in the adult. The nuclear-chain fibres develop in the same way; myoblasts fuse to form satellite myotubes that mature in pseudopodial apposition to one of the other fibres within its basement membrane. This apposition consists of extensions of sarcoplasm from the developing myotube into the supporting fibre. By the 4-day postnatal stage the full adult complement of 4 intrafusal muscle fibres is present, although ultrastructural variations, seen in the adult, are not differentiated. The fusimotor innervation begins to arrive at birth, but is not mature until the 12th postnatal day, when the myofibrillar ultrastructural differentiation, including the loss of the M-line in the large-diameter bag fibre, is complete. The periaxial space appears at the same time. It is suggested that the sequential development of the intrafusal fibres is a reflexion of the decreasing morphogenetic effect of the afferent innervation, whereas the role of the fusimotor innervation is in ultrastructural, myofibrillar differentiation.

Plasticity in mammalian skeletal muscle

1977 ◽  
Vol 278 (961) ◽  
pp. 295-305 ◽  
Keyword(s):  
Skeletal Muscle ◽  
Peripheral Nerve ◽  
Motor Nerve ◽  
Contractile Proteins ◽  
Biochemical Changes ◽  
Muscle Fibres ◽  
Mammalian Skeletal Muscle ◽  
Motor Innervation ◽  
Nerve Impulses ◽  
Contractile Characteristics

While it has been recognized for many years that different limb muscles belonging to the same mammal may have markedly differing contractile characteristics, it is only comparatively recently that it has been demonstrated that these differences depend upon the motor innervation. By appropriately changing the peripheral nerve innervating a mammalian skeletal muscle, it is possible to change dramatically the contractile behaviour of the reinnervated muscle. The manner by which the motor innervation determines the nature of a muscle fibre’s contractile machinery is not completely understood, but it appears that the number and pattern of motor nerve impulses reaching the muscle play an important role. The biochemical changes occurring within muscle fibres whose contractile properties have been modified by altered motor innervation include the synthesis of different contractile proteins.

The Croonian Lecture, 1967: The activation of striated muscle and its mechanical response

1971 ◽  
Vol 178 (1050) ◽  
pp. 1-27 ◽  
Keyword(s):  
Mechanical Response ◽  
Striated Muscle ◽  
Motor Nerve ◽  
Chemical Activation ◽  
Small Diameter ◽  
Trunk Muscles ◽  
Muscle Fibres ◽  
Minor Importance ◽  
Main Theme ◽  
Striated Muscles

Since the end of the 1939-45 war, the task of someone trying to understand muscular contraction has become in some respects easier, and in others more difficult. On the credit side, straightforward explanations are now available—and well established—for the main events in neuromuscular transmission, propagation of the action potential, the inward spread of an activating process, chemical activation of the myofibrils, and the sliding filament process of length change. On the other side new properties, new structures and new substances have turned up which cannot yet be fitted into any comprehensive scheme. Further, we are still totally in the dark about the actual molecular processes involved even in those steps for which clear explanations are available at the electrophysiological or electronmicroscopical level. Yet another complication is the extraordinary variety of muscle types that are being discovered, even among such thoroughly studied groups of animals as amphibians and mammals. I have been repeatedly struck by cases where the investigation of muscle has been held up by a false assumption based on the supposition that different kinds of contractile materials must work in the same way. For example, it has often been argued that smooth muscle and striated muscle are essentially similar, and therefore the striations are of only minor importance; this argument was given, for example, by Bernstein (1901, p. 284). The still more general argument that the nature of the ‘contractility’ of muscle should be looked for in the supposedly simpler processes of protoplasmic movement had been the main theme of a book by Verworn (1892). This attitude was, I am sure, one of the main reasons for the almost complete disregard of the striations by physiologists and biochemists between about 1910 and 1950. Again, the elucidation of the slow motor system of certain striated muscle fibres, present in probably all vertebrates, was delayed for many years by the discovery that in mammals even the slow postural activity of limb and trunk muscles is accompanied by propagated action potentials characteristic of fast motor systems. It was widely assumed on this basis that ‘tonic’ contractions in all vertebrate striated muscles consisted of asynchronous twitches or unfused tetani in scattered motor units, and most physiologists came to disregard the numerous indications—physiological and pharmacological (Langley 1913; Sommerkamp 1928; Wachholder & von Ledebur 1930) as well as histological (see Krüger (1952) for references both to his own work in the thirties and to other work)—of the existence of a second, slow, system in skeletal muscles of the frog. The very slow contractions elicited in the familiar gastrocnemius muscle of the frog by stimulating small-diameter motor-nerve fibres (Tasaki & Kano 1942; Tasaki & Mizutani 1944; Tasaki & Tsukagoshi 1944) came as a complete surprise to most physiologists, and received little attention until the matter was taken up by Kufiler and his colleagues (e.g. Kuffler & Vaughan Williams 1953). The astonishing range of structural diversity that becomes apparent when one looks at the arthropods as well as the vertebrates has recently been emphasized by Hoyle (1967).

Muscle receptors in cephalopods

1965 ◽  
Vol 161 (984) ◽  
pp. 392-402 ◽  
Keyword(s):  
Nerve Cells ◽  
Octopus Vulgaris ◽  
Muscle Fibres ◽  
Sepia Officinalis ◽  
Muscle Receptors ◽  
Intramuscular Nerve ◽  
Nerve Cords

Multipolar nerve cells with the characteristics of muscle receptors have been shown in the arms of Octopus vulgaris . The dendrites of these cells branch out into the muscle fibres and their axons make their way to small, intramuscular ganglion centres (ganglion of the sucker and intramuscular nerve cords), in which they seem to end. Multipolar nerve cells with characteristics similar to those of the cells described in Octopus have also been shown in the lip of Sepia officinalis . Such evidence permits one to think that these structures are more frequent in the cephalopods than has been suspected hitherto and it confirms the presence of a system of proprioceptors.

Activity patterns of motoneurons in the spinal dogfish in relation to changing Active locomotion

1990 ◽  
Vol 330 (1258) ◽  
pp. 329-339 ◽  
Keyword(s):  
Tactile Stimulation ◽  
Motor Nerve ◽  
Activity Patterns ◽  
Emg Activity ◽  
Muscle Fibres ◽  
Cycle Period ◽  
Nerve Activity ◽  
Group I ◽  
Group Ii ◽  
Active Swimming

Rhythmic motoneuronal activity was recorded from segmental motor nerves of moving (spinal swimming) and paralysed (fictive swimming) spinal dogfish ( Scyliorhinus canicula ), and, in the paralysed preparation, microelectrode recordings were made from spinal cord motoneurons. The motoneurons could be divided into two groups, according to their activity patterns. Group I ( n = 31) were inactive during Active swimming and did not respond to gentle tactile stimulation; when recorded from intracellularly they showed stable to weakly oscillating (< 1 mV) membrane potentials. Group II ( n = 15) fired bursts of action potentials in phase with the motor nerve activity, which were superimposed upon larger (up to 17 mV) depolarizations, and responded to gentle tactile stimulation. Two of these cells discharged also in the interburst interval of the nerve activity. Decreases in cycle period of the Active swimming (i.e. increases in locomotor frequency) were instantaneously accompanied by increases in the amplitude of the rectified and integrated motor nerve signal, which represents peak activity of group II motoneurons, and decreases in the duration of the motor burst. Similar instantaneous changes were seen in the firing frequency and burst duration of individual group II motoneurons. The conformity between unit and population behaviour with changing speed of Active swimming, and the close correspondence observed between the form of the excitatory postsynaptic potentials recorded from individual motoneurons and the form of the integrated neurogram, suggest that the group II motoneurons receive a common excitatory drive. Re- and decruitment of motoneurons were virtually absent during these changes of speed. During unstimulated spinal swimming, regular left—right alternating EMG activity is recorded from the red but not from the white part of the myotome. The ratio of group I to group II motoneurons (31:15) recorded in this study agrees with the previously reported proportion of axons in the spinal motor nerve that project to the white and red muscle fibres, respectively. We suggest, therefore, that group II motoneurons innervate the red and superficial muscle fibres and group I the white fibres. The different activity patterns of the two motoneuronal groups in the spinal fish probably reflect the different ways the red and white muscle systems are used during locomotion

scholarly journals THE MODULATORY EFFECTS OF SEROTONIN, NEUROPEPTIDE F1 AND PROCTOLIN ON THE RECEPTOR MUSCLES OF THE LOBSTER ABDOMINAL STRETCH RECEPTOR AND THEIR EXOSKELETAL MUSCLE HOMOLOGUES

1993 ◽  
Vol 174 (1) ◽  
pp. 363-374
Author(s):  
V. M. Pasztor ◽  
L. B. Golas
Keyword(s):  
Muscle Fibres ◽  
Sensory Afferents ◽  
Tension Development ◽  
Sensory Neurones ◽  
Multiple Loci ◽  
Receptor Organ ◽  
Two Measures ◽  
Low Incidence ◽  
Passive Stretch ◽  
Receptor Muscle

The muscle receptor organ (MRO) of the lobster is a complex proprioceptive system lying in parallel with the axial extensor musculature. Two peripherally located sensory neurones extend stretch-sensitive dendrites into individual receptor muscle strands one tonic (RM1) and one phasic (RM2). Previous studies have shown that the sensitivity of the sensory neurones to passive stretch could be enhanced by serotonin and proctolin. Here we show that the receptor muscles and their exoskeletal muscle homologues are also responsive to serotonin, proctolin and, in addition, to neuropeptide F1 (TNRNFLRF-NH2). Two measures of motor performance were enhanced by all three neurohormones: EJP amplitude and nerve-evoked tension development. Serotonin was the most effective modulator of both tonic and phasic muscles. F1 had powerful effects on the phasic extensor muscle. A low incidence of tonic muscle fibres with synapses responding to the neurohormones suggests that there are distinct populations of synapses: those sensitive to specific modulators and others that are insensitive. These findings, taken together with the enhancing effects of modulation on the primary sensory afferents, suggest that circulating neurohormones may act at multiple loci in the MRO system in a concerted and hormone-specific manner to alter the flow of proprioceptive feedback.

Propagation of electric activity in motor nerve terminals

1965 ◽  
Vol 161 (985) ◽  
pp. 453-482 ◽  
Keyword(s):  
Motor Nerve ◽  
Electric Activity ◽  
Muscle Fibres ◽  
Nerve Terminals ◽  
Terminal Branch ◽  
Direct Stimulation ◽  
Motor Nerve Terminals ◽  
End Plate ◽  
Synaptic Terminals ◽  
Set Up

External micro-electrodes were used to stimulate non-myelinated motor nerve terminals and to record pre- and post-synaptic responses at the neuromuscular junction of the frog. The synaptic terminals of the motor axon are electrically excitable. Antidromic nerve impulses can be set up by local stimulation of terminals along the greater part of their length. Presynaptic spikes can be recorded from the non-myelinated terminal parts of motor axons. As the impulse proceeds towards the tip of the terminal branch, the shape of the spike changes from a predominantly negative to a predominantly positive-going wave. Similar changes occur in muscle fibres near their tendon junctions, and can be attributed to the special local-circuit conditions at the ‘closed end’ of a fibre. The velocity of impulse propagation in motor nerve endings was determined by three different methods: ( a ) from the latency of antidromic nerve spikes elicited at different points along terminals, ( b ) from two-point recording of spikes along a terminal, ( c ) from the differential latency of focal end-plate potentials recorded at two spots of a myoneural junction. The average velocity obtained by these methods was approximately 0.3 m/s at 20 °C. Extracellular muscle fibre spikes recorded at junctional spots showed no significant differences from those recorded elsewhere, provided the spikes were initiated by direct stimulation and did not coincide with transmitter action. Direct current polarization produces a graded increase in frequency of miniature end-plate potentials when the endings are being depolarized, and sudden high-frequency bursts during excessive hyperpolarization. External two-point recording shows that these bursts arise independently at different spots of the synaptic terminals.

Innervation of the ventral diaphragm of the locust (Locusta migratoria)

1977 ◽  
Vol 69 (1) ◽  
pp. 23-32
Author(s):  
M. Peters
Keyword(s):  
Electrical Stimulation ◽  
Electrical Properties ◽  
Electrical Activity ◽  
Neuromuscular Junctions ◽  
Motor Nerve ◽  
Locusta Migratoria ◽  
Posterior Segment ◽  
Muscle Fibres ◽  
Inspiratory Muscles ◽  
Motor Neurones

1. Innervation and some electrical properties of the locust ventral diaphragm were investigated with electrophysiological and histological methods. 2. Muscle fibres are coupled electrically. Electrical stimulation evokes a graded active membrane response. 3. Each segment is innervated by four motor neurones as follows. Two motor neurones are situated in each abdominal ganglion. Branches of their axons supply the ventral diaphragm in the respective and the next posterior segment. 4. This pattern of innervation was confirmed by axonal Co and Ni staining of the motor nerve endings. 5. Neuromuscular junctions are excitatory. EPSPs show summation but no facilitation. 6. Spontaneous electrical activity of the diaphragm is to a certain degree coupled to activity of the main inspiratory muscles.

A dual effect of cobalt ions on the spontaneous release of transmitter at insect motor nerve terminals

1982 ◽  
Vol 98 (1) ◽  
pp. 353-361
Author(s):  
H. Washio
Keyword(s):  
External Surface ◽  
Motor Nerve ◽  
Reciprocal Relationship ◽  
Muscle Fibres ◽  
Nerve Terminals ◽  
Spontaneous Release ◽  
Dual Effect ◽  
Competitive Antagonist ◽  
Cobalt Ions ◽  
Equilibrium Dissociation

1. The effect of extracellular cobalt on the frequency of miniature excitatory post-synaptic potentials (MEPSPs) was studied in cockroach leg muscle fibres that had been depolarized with 20.8 mM-K saline. 2. Cobalt ions had a dual effect on the spontaneous release of transmitter, an inhibitory action being followed by an acceleratory. A reciprocal relationship between Ca2+ and Co2+ was found for both the inhibitory and acceleratory effects. 3. The equilibrium dissociation constant for Co2+ as a competitive antagonist of spontaneous release ranged from 0.4 to 0.65 mM. It is concluded that Co2+ is much more potent than Mg2+ in suppressing spontaneous transmitter release at the insect neuromuscular junction. The antagonism by extracellular Co2+ appears to occur only at the external surface site on the terminal membrane.

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