Abstract
1. Reflex efferent control of a muscle stretch receptor by a joint proprioceptor of the same limb was studied in an isolated CNS preparation from the shore crab. The influence of 'fictive locomotor' activity on this interjoint reflex was also examined. 2. The thoracic-coxal muscle receptor organ (TCMRO) and the coxo-basal chordotonal organ (CBCO), which monitor movement and position of the first and second joints of the posterior leg, were isolated together with the whole thoracic ganglion complex. The TCMRO, functionally analogous to a mammalian muscle spindle, has two receptor motoneurones. RM1 innervating the receptor muscle alone and RM2 which also supplies the 'extrafusal' promotor muscle. The CBCO is a typical arthropod elastic strand organ, with many sensory neurones but lacking an efferent supply. The TCMRO was fixed at its mid-length, and stretch-hold-release stimuli were applied to the CBCO. Efferent activity was recorded from the cut nerve roots of the four basal limb muscles and intracellularly as excitatory junction potentials (EJPs) from the receptor muscle. 3. A dynamic increase in the frequency of action potentials in RM1 occurred on both stretch and release of the CBCO. During the hold phase the RM1 activity declined from the dynamic response but remained elevated compared to the resting tonic discharge. RM2, identified by EJPs occurring 1:1 with a unit in the promoter nerve, responded in a similar way. 4. One or more promotor motoneurones were usually co-activated with the two receptor efferents in response to input from the CBCO. In a typical example the average spike frequency of RM1 rose from 0 to 27 Hz during the dynamic phases (stretch and release) of the CBCO stimulus, falling to 2.5 Hz during the hold phase, while the corresponding promotor spike frequencies were 25 and 7.5 Hz, respectively. The other three muscle nerves recorded from generally also showed reflex driving by the CBCO. 5. The totally isolated thoracic ganglion could produce a rhythmic, bursting motor output in the absence of any sensory input. During this centrally generated activity the receptor motor innervation was strongly co-activated with the promotor bursts, and the reflex input from the CBCO was overridden or modulated in a phase-dependent manner. 6. The proximally directed interjoint reflex to the receptor muscle probably functions to maintain the tension on the sensory endings of the TCMRO, and so enable them to respond effectively at all times to movements of the basal leg joint.(ABSTRACT TRUNCATED AT 400 WORDS)
Full text
PDF
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Appelberg B., Hulliger M., Johansson H., Sojka P. Fusimotor reflexes in triceps surae elicited by natural stimulation of muscle afferents from the cat ipsilateral hind limb. J Physiol. 1982 Aug;329:211–229. doi: 10.1113/jphysiol.1982.sp014299. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Bräunig P., Hustert R. Proprioceptive control of a muscle receptor organ in the locust leg. Brain Res. 1983 Sep 12;274(2):341–343. doi: 10.1016/0006-8993(83)90715-1. [DOI] [PubMed] [Google Scholar]
- Bush B. M., Vedel J. P., Clarac F. Intersegmental reflex actions from a joint sensory organ (CB) to a muscle receptor (MCO) in decapod crustacean limbs. J Exp Biol. 1978 Apr;73:47–63. doi: 10.1242/jeb.73.1.47. [DOI] [PubMed] [Google Scholar]
- Clarac F., Vedel J. P., Bush B. M. Intersegmental reflex coordination by a single joint receptor organ (CB) in rock lobster walking legs. J Exp Biol. 1978 Apr;73:29–46. doi: 10.1242/jeb.73.1.29. [DOI] [PubMed] [Google Scholar]
- Grillner S. Supraspinal and segmental control of static and dynamic gamma-motoneurones in the cat. Acta Physiol Scand Suppl. 1969;327:1–34. [PubMed] [Google Scholar]
- Heitler W. J. Coupled motoneurones are part of the crayfish swimmeret central oscillator. Nature. 1978 Sep 21;275(5677):231–234. doi: 10.1038/275231a0. [DOI] [PubMed] [Google Scholar]
- Johansson H., Sjölander P., Sojka P. Actions on gamma-motoneurones elicited by electrical stimulation of joint afferent fibres in the hind limb of the cat. J Physiol. 1986 Jun;375:137–152. doi: 10.1113/jphysiol.1986.sp016110. [DOI] [PMC free article] [PubMed] [Google Scholar]
- LAPORTE Y., LLOYD D. P. C. Nature and significance of the reflex connections established by large afferent fibers of muscular origin. Am J Physiol. 1952 Jun;169(3):609–621. doi: 10.1152/ajplegacy.1952.169.3.609. [DOI] [PubMed] [Google Scholar]
- Lundberg A., Malmgren K., Schomburg E. D. Role of joint afferents in motor control exemplified by effects on reflex pathways from Ib afferents. J Physiol. 1978 Nov;284:327–343. doi: 10.1113/jphysiol.1978.sp012543. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Roberts A., Bush B. M. Coxal muscle receptors in the crab: the receptor current and some properties of the receptor nerve fibres. J Exp Biol. 1971 Apr;54(2):515–524. doi: 10.1242/jeb.54.2.515. [DOI] [PubMed] [Google Scholar]
- Skorupski P., Sillar K. T. Phase-dependent reversal of reflexes mediated by the thoracocoxal muscle receptor organ in the crayfish, Pacifastacus leniusculus. J Neurophysiol. 1986 Apr;55(4):689–695. doi: 10.1152/jn.1986.55.4.689. [DOI] [PubMed] [Google Scholar]