|
| |
|
|
|
|
||||
| Home Help Feedback Subscriptions Archive Search Table of Contents | ||||
Reflex Control of Abdominal Flexor Muscles in the Crayfish : II. The Tonic System
1 Department of Biological Sciences, Stanford University, Stanford, California
1. Fibres from the tonic, superficial abdominal flexor muscles in the crayfish receive a complex, highly polyneuronal innervation from among five motor axons and one inhibitor. All efferent nerve fibres show some degree of ‘spontaneous’ activity.
2. The muscle fibres therefore exhibit a constant flux of membrane potential, and hence of tension, in intact preparations. Depolarization is the result of facilitation and/or summation of junctional potentials of various amplitudes, and in some fibres of superimposed electrogenic responses. Neighbouring fibres tend to show similar innervation patterns, more distant ones dissimilar ones.
3. No useful distinction may be made between ‘fast’ and ‘slow’ motor axons. A given axon may produce junctional potentials of very different amplitudes (and some what different rise-times) in neighbouring muscle fibres while another exhibits a precisely reciprocal relationship. The largest axon produces facilitating junctional potentials in all the muscle fibres it innervates, but others may exhibit facilitation in one muscle fibre and antifacilitation in another.
4. Most muscle fibres are innervated by two or three excitatory axons; fibres with single, quadruple or quintuple motor innervation are relatively rare. There is a pronounced tendency for fibres with a rich excitatory innervation to receive the inhibitor as well. The innervation is not shared equally among motor axons: one serves over 90% of the muscle fibres, and two others 20% or less. Statistical analysis of the combinations of motor axons serving muscle fibres reveals that these are apparently random, with all variations from randomness accountable on the grounds of broad regional differences in distribution.
5. The motor axons are selectively activated by specific reflex inputs. Since muscle fibres receive, on the average, only a restricted sample of the available motor supply, it follows that they participate differentially in different reflex actions. Evidence is presented that the firing pattern of motor nerves is appropriate for the temporal properties of their neuromuscular junctions.
6. Reflex inhibition is accomplished by central inhibition of all excitatory motor outflow, accompanied by reciprocal firing in the inhibitor axon. This and the fact that less than half the muscle fibres receive inhibitory innervation demonstrate that, in contrast to the one other crustacean system analysed, reflex inhibition is primarily a central event. Peripheral inhibition in the slow flexor system must serve mainly as a device to achieve repolarization and thus terminate contractions. Such action necessarily depends upon post-synaptic rather than presynaptic mechanisms.
Note:
On leave from the Department of Physiology, University of Tokyo Medical College.
Submitted on January 13, 1965
This article has been cited by other articles:
|
|
 |
|
  H. Atwood PARALLEL `PHASIC' AND `TONIC' MOTOR SYSTEMS OF THE CRAYFISH ABDOMEN J. Exp. Biol., July 15, 2008; 211(14): 2193 - 2195. [Full Text] [PDF]
|
|
|
|
 |
|
 A. G. Millar, R. S. Zucker, G. C. R. Ellis-Davies, M. P. Charlton, and H. L. Atwood Calcium Sensitivity of Neurotransmitter Release Differs at Phasic and Tonic Synapses J. Neurosci., March 23, 2005; 25(12): 3113 - 3125. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. G. Millar and H. L. Atwood Crustacean Phasic and Tonic Motor Neurons Integr. Comp. Biol., February 1, 2004; 44(1): 4 - 13. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 N. Rumpal and G. A. Lnenicka Ca2+ Clearance at Growth Cones Produced by Crayfish Motor Axons in an Explant Culture J Neurophysiol, June 1, 2003; 89(6): 3225 - 3234. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. G. Millar, H. Bradacs, M. P. Charlton, and H. L. Atwood Inverse Relationship between Release Probability and Readily Releasable Vesicles in Depressing and Facilitating Synapses J. Neurosci., November 15, 2002; 22(22): 9661 - 9667. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. Duch and R. B. Levine Remodeling of Membrane Properties and Dendritic Architecture Accompanies the Postembryonic Conversion of a Slow into a Fast Motoneuron J. Neurosci., September 15, 2000; 20(18): 6950 - 6961. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Msghina, A. G. Millar, M. P. Charlton, C. K. Govind, and H. L. Atwood Calcium Entry Related to Active Zones and Differences in Transmitter Release at Phasic and Tonic Synapses J. Neurosci., October 1, 1999; 19(19): 8419 - 8434. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B. Mccarthy and D. Macmillan Control of abdominal extension in the freely moving intact crayfish cherax destructor. I. Activity Of the tonic stretch receptor J. Exp. Biol., January 1, 1999; 202(2): 171 - 181. [Abstract] [PDF]
|
|
|
|
|
|
B. Mccarthy and D. Macmillan Control of abdominal extension in the freely moving intact crayfish cherax destructor. II. Activity Of the superficial extensor motor neurones J. Exp. Biol., January 1, 1999; 202(2): 183 - 191. [Abstract] [PDF]
|
|
|
|
|
|
K. M. Krause, J. Pearce, and C. K. Govind Regeneration of Phasic Motor Axons on a Crayfish Tonic Muscle: Neuron Specifies Synapses J Neurophysiol, August 1, 1998; 80(2): 994 - 997. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Msghina, C. K. Govind, and H. L. Atwood Synaptic Structure and Transmitter Release in Crustacean Phasic and Tonic Motor Neurons J. Neurosci., February 15, 1998; 18(4): 1374 - 1382. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. L. Ray, F. Clarac, and D. Cattaert Functional Analysis of the Sensory Motor Pathway of Resistance Reflex in Crayfish. I. Multisensory Coding and Motor Neuron Monosynaptic Responses J Neurophysiol, December 1, 1997; 78(6): 3133 - 3143. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. Pearce, K. M. Krause, and C. K. Govind Muscle Fibers in Regenerating Crayfish Motor Nerves J Neurophysiol, December 1, 1997; 78(6): 3498 - 3501. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P. V. Nguyen, L. Marin, and H. L. Atwood Synaptic Physiology and Mitochondrial Function in Crayfish Tonic and Phasic Motor Neurons J Neurophysiol, July 1, 1997; 78(1): 281 - 294. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 K. J. Futamachi Acetylcholine:Possible Neuromuscular Transmitter in Crustacea Science, March 24, 1972; 175(4028): 1373 - 1375. [Abstract] [PDF]
|
|
|
|
|
|
C. H. Page and P. G. Sokolove Crayfish Muscle Receptor Organ: Role in Regulation of Postural Flexion Science, February 11, 1972; 175(4022): 647 - 650. [Abstract] [PDF]
|
|
|
|
|
|
D. Kennedy, W. H. Evoy, and J. T. Hanawalt Release of Coordinated Behavior in Crayfish by Single Central Neurons Science, November 18, 1966; 154(3751): 917 - 919. [Abstract] [PDF]
|
|
