scholarly journals PRIMITIVE NERVOUS SYSTEMS. A SENSORY NERVE-NET IN THE POLYCLAD FLATWORMNOTOPLANA ACTICOLA

1973 ◽  
Vol 145 (2) ◽  
pp. 352-359 ◽  
Author(s):  
HAROLD KOOPOWITZ
Keyword(s):  
Sensory Nerve ◽  
Nervous Systems ◽  
Nerve Net ◽  
Primitive Nervous Systems

scholarly journals The Nerve-Net of the Actinozoa

1935 ◽  
Vol 12 (2) ◽  
pp. 156-164
Author(s):  
C. F. A. PANTIN
Keyword(s):  
Arbitrary Element ◽  
Primary Response ◽  
Reverse Direction ◽  
Neuromuscular System ◽  
Nervous Systems ◽  
Nerve Net ◽  
Conducting Path ◽  
Synaptic Junctions ◽  
Regular Relation

1. Polarity exists in Calliactis, particularly in the tentacles. In these, there is a centripetal polarity of anatomical origin, but there is in addition a physiological polarity running centrifugally. More stimuli are required to facilitate a conducting path centrally from a point on the tentacle than in the reverse direction. Polarity may originate by the development of differential facilitation rates. 2. In some individuals, a kind of after-discharge is observed. A series of one or more extra contractions follows the primary response to a stimulus. Though these appear only after a stimulus has been given they are only indirectly caused by it. Their presence or absence cannot be predicted and seems to bear no relation to the strength of the stimulus. They introduce an arbitrary element into the otherwise singularly regular relation between stimulus and response. 3. Several possible sources for the phenomenon are considered, including synaptic junctions between conducting units of the nerve net, but there are difficulties in accepting any of them. 4. The nerve net of Calliactis possesses many of the properties of the nervous systems of more highly organised animals. The danger is pointed out of employing the unique skeletal neuromuscular system of the Vertebrata as the standard by which the nervous arrangement of other phyla are to be compared.

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.

Primitive Nervous Systems

Nature ◽  
1968 ◽  
Vol 220 (5167) ◽  
pp. 623-623
Author(s):  
G. A. HORRIDGE
Keyword(s):  
Nervous Systems ◽  
Primitive Nervous Systems
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