Primitive nervous systems: electrophysiology of the pharynx of the polyclad flatworm, Enchiridium punctatum

1976 ◽  
Vol 65 (3) ◽  
pp. 627-642
Author(s):  
G. Stone ◽  
H. Koopowitz
Keyword(s):  
Motor Activity ◽  
Electrical Activity ◽  
Behavioural Response ◽  
Nervous Systems ◽  
Stimulus Parameters ◽  
Conduction Velocities ◽  
Primitive Nervous Systems ◽  
Behavioural Sequence ◽  
Aperture Closure ◽  
Muscle Potential

1. Electrical activity accompanying motor activity can be recorded from the excised pharynx of Enchiridium punctatum. Multiple stimuli elicit behaviour which consists of an initial aperture closure followed by extension and then peristalsis. If the stimulus parameters are increased the preparation bends from side to side instead of proceeding through the behavioural sequence. Bending appears to inhibit other movements differentially. 2. The conduction involved with peristalsis is polarized and proceeds in a proximal direction. 3. With stimulus intensities greater than those needed to produce the behavioural response an initial muscle potential (IMP) is evoked. The IMP is frequency sensitive. Maximum facilitation occurs within 100 ms and drops to 50% of maximum within 250 ms. 4. Conduction velocities of the IMP range from 0–05 m s-1 to 1-9 m s-1. Conduction velocities appear to increase with facilitation.

scholarly journals Co-Ordination of Pedal-Disk Detachment in the Sea Anemone Calliactis Parasitica

1969 ◽  
Vol 51 (2) ◽  
pp. 387-396
Author(s):  
I. D. MCFARLANE
Keyword(s):  
Electrical Stimulation ◽  
Electrical Activity ◽  
Mechanical Stimulation ◽  
Average Frequency ◽  
Conduction System ◽  
Identical Stimulus ◽  
Slow Conduction ◽  
Calliactis Parasitica ◽  
Behavioural Sequence ◽  
Stimulation Of

1. Electrical activity has been recorded from the sphincter region of Calliactis parasitica during the behavioural sequence in which the anemone detaches from the substrate and attaches to a Buccinum shell. The ectodermal slow-conduction system (SS1) fires repetitively, the majority of observed pulses occurring in the period prior to detachment (a typical example is 25 SS1pulses at an average frequency of 1 pulse/7 sec.). Shell-tentacle contact is essential for stimulation of SS1activity. 2. Mechanical stimulation of the column excites the SS1, and 30 stimuli at a frequency of about one shock/5 sec. give pedal disk detachment. 3. Electrical stimulation of the ectoderm excites the SS1and about 30 stimuli at frequencies between one shock/3 sec. and one shock/9 sec. produce detachment. Detachment and the SS1 have an identical stimulus threshold. It is concluded that detachment is co-ordinated by the SS1.

Interactions Between Neurones Mediating Tuft Withdrawal in Tritonia Hombergi

1974 ◽  
Vol 61 (3) ◽  
pp. 655-666
Author(s):  
D. A. DORSETT ◽  
A. O. D. WILLOWS
Keyword(s):  
Motor Activity ◽  
Stimulus Intensity ◽  
Large Amplitude ◽  
Sensory Input ◽  
Behavioural Response ◽  
Spike Pattern ◽  
General Increase ◽  
Repeated Use ◽  
Three Stages ◽  
Central Excitability

The seven neurones that command the three stages of branchial tuft withdrawal interact by electrotonic and chemically mediated polysynaptic pathways. The pleural tuft retractors, L and R Pl 6, make electrotonic synapses with the ipsilateral neuronesPd2, which cause retraction of the tips of the tufts. The chemically transmitting pathways, between these and other retractor neurones, are mostly reciprocal and can be classified as weak or strong. The former are small in amplitude, with long latencies (1-3 sec) and are labile to repeated activation; the latter are of large amplitude and shorter latency (0·5-0·8 sec), but may still show decrement with repeated use. Frequently the p.s.p. shows indications of 1:1 correlation with the spike pattern in the driven neurone, but the long latencies require the presence of at least one interneurone in the pathway. The progressive spread of the behavioural response (withdrawal of the tips, complete unilateral withdrawal, complete bilateral withdrawal of all tufts), which occurs with increasing stimulus intensity, is not dependent on a central hierarchy in the activation of the tuft retractor neurones. Reciprocal feedback leads to a general increase in central excitability, the threshold for more extensive responses being probably determined largely by the sensory input to individual neurones. The unique pleural cell R Pl 5 is exceptional, both in the variety of motor activity it commands and in the absence of reciprocal connexions from other retractor neurones.

Reflex effect of esophageal distension on respiratory muscle activity and pressure

1989 ◽  
Vol 66 (2) ◽  
pp. 536-541 ◽  
Author(s):  
A. Oliven ◽  
M. Haxhiu ◽  
S. G. Kelsen
Keyword(s):  
Motor Activity ◽  
Electrical Activity ◽  
Respiratory Muscle ◽  
Abdominal Cavity ◽  
Respiratory Muscles ◽  
Abdominal Pressure ◽  
Lung Inflation ◽  
Rib Cage ◽  
Expiratory Muscles ◽  
Crural Diaphragm

The electrical activity of the respiratory skeletal muscles is altered in response to reflexes originating in the gastrointestinal tract. The present study evaluated the reflex effects of esophageal distension (ED) on the distribution of motor activity to both inspiratory and expiratory muscles of the rib cage and abdomen and the resultant changes in thoracic and abdominal pressure during breathing. Studies were performed in 21 anesthetized spontaneously breathing dogs. ED was produced by inflating a balloon in the distal esophagus. ED decreased the activity of the costal and crural diaphragm and external intercostals and abolished all preexisting electrical activity in the expiratory muscles of the abdominal wall. On the other hand, ED increased the activity of the parasternal intercostals and expiratory muscles located in the rib cage (i.e., triangularis sterni and internal intercostal). All effects of ED were graded, with increasing distension exerting greater effects, and were eliminated by vagotomy. The effect of increases in chemical drive and lung inflation reflex activity on the response to ED was examined by performing ED while animals breathed either 6.5% CO2 or against graded levels of positive end-expiratory pressure (PEEP), respectively. Changes in respiratory muscle electrical activity induced by ED were similar (during 6.5% CO2 and PEEP) to those observed under control conditions. We conclude that activation of mechanoreceptors in the esophagus reflexly alters the distribution of motor activity to the respiratory muscles, inhibiting the muscles surrounding the abdominal cavity and augmenting the parasternals and expiratory muscles of the chest wall.

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