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Title: Structure and contractile properties of the ostial muscle (musculus orbicularis ostii) in the heart of the American lobster
Authors: Cavey, Michael J.
Yazawa, T.
Wilkens, J. L.
ter Keurs, H. E. D. J.
Keywords: Biology
Issue Date: 10-Aug-1999
Publisher: Springer-Verlag
Citation: T. Yazawa, J. L. Wilkens, H. E. D. J. ter Keurs, M. J. Cavey "Structure and contractile properties of the ostial muscle (musculus orbicularis ostii) in the heart of the American lobster" J Comp Physiol B (1999) 169: 529-537
Abstract: "Venous" blood enters the crustacean heart through bivalved ostia. Each ostium is a discrete ana- tomical unit that remains functional even when isolated from the heart. Muscle ®bers produce overshooting ac- tion potentials that have a plateau of variable duration in response to nervous drive from the cardiac ganglion or during trains of electrical stimuli. Contractions show summation and facilitation when stimulated by trains of stimuli delivered at rates greater than 0.5 s)1 and 0.2 s)1, respectively. Contraction amplitude increases with stimulating impulse frequency and train duration. Maximum force occurs at 1.2 times the slack length. The morphology of ostial ®bers resembles that of myocardial ®bers. Interconnected bundles of myo®laments occur in both the ostial ®bers and the myocardial ®bers. In ostial and myocardial ®bers, the myo®lament bundles are in- vested by perforated sheets of sarcoplasmic reticulum, and these sheets interface with a network of sarcolemmal tubules to form dyadic interior couplings at the level of the sarcomeric H-bands. The contractile apparatus originates and terminates at intermediate junctions on the transverse cellular boundaries, and the lateral sur- faces of the muscle ®bers are linked by a modest number of communicating (gap) junctions.
ISSN: 0174-1578
Appears in Collections:Cavey, Michael J.

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