Three types of muscles in the heart
There are two types in the cardiac muscles: The ordinary
cardiac
muscles and the ostium muscle. They are both controled by common
motor neurons in the cardiac ganglion.
There also are the cardio-arterial valves between the ventricle
and the arteries. The muscles of the cardio-arterial valves are regulated
by motor nerves from the CNS.
... also see the heart as a pump
Coodinated contraction of cardiac muscles
These pictures are the snapshots of crayfish heartbeat taken at the
interval of 1/15 sec. The lateral ostium (valvular opening) and
the poterior end of the heart are visible in each frame. Closure
of the ostium starts just before the contraction of the heart wall
().
Acting as a simple pump,
quick
closure of the valuvular openings is important to pump out efficiently
the hemolymph to the arteries. The closure of the ostia is induced
by rapid contraction of the ostium muscles which is innervated
by the motor neurons in the cardiac ganglion. Controled by the same
motoneurons, how can the ostium muscles contract faster than the cardiac
muscle?
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Do the ostium muscles receive motor signals before the cardiac muscles
do?
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Are there any differences in neuromuscular transmission?
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Any differences in the electrical and contractile properties of these
muscles?
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How about the metabolism in these muscles?
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How do these muscles differentiate during the early developmental stages?
You will see my results at 5th
International Congress of Comparative Biochemistry and Physiology on
August 23-28 1999 in Calgary, Alberta.
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