scholarly journals Abdominal postural motor responses initiated by the muscle receptor organ in lobster depend upon centrally generated motor activity

1992 ◽  
Vol 162 (1) ◽  
pp. 167-183
Author(s):  
S. C. Sukhdeo ◽  
C. H. Page
Keyword(s):  
Motor Activity ◽  
Motor Neurons ◽  
Procambarus Clarkii ◽  
Homarus Americanus ◽  
Abdominal Muscle ◽  
Sensory Response ◽  
Reflex Responses ◽  
Muscle Receptor ◽  
Postural Reflex ◽  
Receptor Organ

1. Stretch stimulation of the abdominal muscle receptor organ of the lobster Homarus americanus initiated spike discharge of its tonic sensory neuron (SR1). This sensory response evoked a series of tonic postural reflex responses in the motor neurons that innervate the superficial extensor and flexor muscles of the abdominal postural system. The type of motor response depended on whether a flexion or extension pattern of spontaneous activity was being generated by the postural efferents. Spontaneous shifts between these centrally generated motor activities completely changed the SR1-evoked reflex responses. 2. During spontaneous centrally initiated flexion activity, tonic SR1 neuron discharge elicited an assistance response that included excitation of a medium-sized flexor excitor (f3) and the peripheral extensor inhibitor (e5), and inhibition of at least one extensor excitor. Neither the other flexor excitors nor the peripheral flexor inhibitor (f5) were affected by SR1 excitation. 3. During spontaneous centrally initiated extension activity, SR1 activity elicited a response that included excitation of the extensor excitors and the flexor peripheral inhibitor (f5) only, f3 and e5 spontaneous activities were unchanged. This response was a resistance reflex, since SR1 discharge normally resulted from an imposed abdominal flexion. 4. The SR1-initiated control of postural motor activity in lobster differs from previously published results in the crayfish Procambarus clarkii.

Phase-dependent reversal of reflexes mediated by the thoracocoxal muscle receptor organ in the crayfish, Pacifastacus leniusculus

1986 ◽  
Vol 55 (4) ◽  
pp. 689-695 ◽  
Author(s):  
P. Skorupski ◽  
K. T. Sillar
Keyword(s):  
Motor Neurons ◽  
Negative Feedback ◽  
Positive Feedback ◽  
Motor Output ◽  
Dependent Manner ◽  
Muscle Receptor ◽  
Reflex Pathways ◽  
Receptor Organ ◽  
Positive And Negative Feedback ◽  
Central Excitability

Both negative feedback, resistance reflexes and positive feedback, assistance reflexes are mediated by the thoracocoxal muscle receptor organ (TCMRO) in the crayfish, depending on the central excitability of the preparation. In this paper we present evidence that the velocity-sensitive afferent T fiber of the TCMRO may elicit either resistance or assistance reflexes in different preparations. In preparations displaying assistance reflexes, the S and T fibers of the TCMRO exert reciprocal effects on leg motor neurons (MNs). The S fiber excites promotor MNs (negative feedback) and inhibits remotor MNs, the T fiber excites remotor MNs (positive feedback) and inhibits promotor MNs. During reciprocal motor output of promotor and remotor MNs, reflexes mediated by the TCMRO are modulated in a phase-dependent manner. The TCMRO excites promotor MNs during their active phases (negative feedback) but inhibits them during their reciprocal phases. Remotor MNs are excited by the TCMRO during their active phases (positive feedback). It is proposed that depolarizing central inputs that occur in the S and T fibers at opposite phases of the motor output cycle (21) facilitate the output effects of each afferent in alternation, effectively mediating a phase-dependent shift between the effects of one afferent and the other. The implications of central modulation of reflex pathways and the possible functions of positive and negative feedback reflexes during locomotion are discussed.

Sensory feedback and central afferent interaction in the muscle receptor organ of the crab, Carcinus maenas

1996 ◽  
Vol 76 (2) ◽  
pp. 788-798 ◽  
Author(s):  
M. Wildman ◽  
A. Cannone
Keyword(s):  
Action Potentials ◽  
Sensory Feedback ◽  
Carcinus Maenas ◽  
Small Diameter ◽  
Sensory Response ◽  
Fiber Direction ◽  
Single Action ◽  
Muscle Receptor ◽  
Leg Muscles ◽  
Receptor Organ

1. An interaction exists between two proprioceptive afferent neurons innervating the thoracic-coxal muscle receptor organ (TCMRO) of the crab, Carcinus maenas. Intracellular recordings were made from the extraganglionic regions of the afferents in order to characterize this interaction and its effects on sensory feedback. 2. A current-induced depolarization of the nonspiking T fiber of the TCMRO results in a depolarization of the P fiber, a small-diameter (7 microns) neuron innervating the same receptor. This interaction is graded in amplitude, and may result in a single action potential being superimposed on the graded response of the P fiber. A hyperpolarization of the T fiber has a smaller effect on the P fiber than a depolarization of similar amplitude. The interaction is rectified in a T- to P-fiber direction, and has a minimum central delay of approximately 3.6 ms. 3. The site of the interaction between the afferents is situated centrally, within the thoracic ganglion. Action potentials evoked in the P fiber by a T-fiber depolarization propagate actively and antidromically to the periphery. 4. Central modulation of the interaction occurs, because the amplitude of a T-fiber-induced depolarization is reduced in the P fiber during centrally generated spontaneous bursts of activity in the motoneurons of basal leg muscles. 5. Because of the interaction between T and P fibers, action potentials recorded from the peripheral portion of the P fiber during receptor stretch may be either orthodromic, resulting directly from the effects of the stretch on the sensory endings of the P fiber, or antidromic, resulting from the central input from the T fiber. 6. The T- to P-fiber interaction may serve to extend the dynamic sensitivity range of the P fiber, in particular by amplifying its sensory response at short receptor lengths and low velocities of stretch.

The role of the muscle receptor organ in the control of abdominal extension in the crayfish, Cherax destructor

1995 ◽  
Vol 198 (11) ◽  
pp. 2253-2259 ◽  
Author(s):  
B Mccarthy ◽  
D Macmillan
Keyword(s):  
Constant Load ◽  
Abdominal Muscle ◽  
Muscle Receptor ◽  
Complete Extension ◽  
Cherax Destructor ◽  
Before And After ◽  
Error Detector ◽  
Receptor Organ ◽  
Servo Loop

A platform was lowered from beneath suspended crayfish, Cherax destructor, to evoke slow abdominal extension. The movements were filmed and the length between segments plotted as a function of time. Unlike abdominal flexion, which starts posteriorly and progresses anteriorly, extension occurs at all joints simultaneously. Although the duration of extension varied from trial to trial for an individual, the movement was organised in a stereotyped manner: the abdomen achieved a consistent position for any given proportion of the time for complete extension. We examined the role of the abdominal muscle receptor organs (MROs) in extension by cutting the nerves of selected MROs to abolish their input. The extension movement was measured before and after nerve section for animals with either unloaded or loaded abdomens. Removal of MRO input had no significant effect on extension of the unloaded abdomen. In animals with a loaded abdomen, the extension at joints spanned by sectioned MROs was slowed, whereas that at joints with intact MROs was not. The findings are consistent with the hypothesis that the MRO is an error detector in a servo-loop controlling abdominal position. The results provide the first demonstration that this load-compensating reflex loop operates during naturally evoked extension of the abdomen under constant load.

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