Summary
The bilateral paired hearts of the medicinal leech are controlled by a set of segmental heart motor neurons (HE cells) which are in turn controlled, via inhibitory synapses, by a set of segmental heart interneurons (HN cells). The HE cells fire in rhythmic impulse bursts because their steady discharge is periodically inhibited by the HN cells.
-
1)
With the identification of an additional pair of HN cells in segmental ganglion 1 and the elucidation of several synaptic connections between HN cells a more complete heart control circuit diagram is now available. This circuit diagram accounts for the observed activity cycles of the various HN and HE cells and consequently for the behavior of the hearts themselves.
-
2)
The bilaterally paired HE cells are coordinated by the HN cells such that the segmental heart tube sections on one side constrict in a caudorostral sequence to produce a rear-to-front peristalsis, while the segmental heart tube sections on the other side constrict nearly synchronously (non-peristaltically). This difference in the coordination modes of the two hearts is not permanent, and reciprocal coordination mode transitions occur every 10–50 heartbeat cycles. Cell HN(5) is phasically active on the side of the non-peristaltic heart tube and completely inactive on the side of the peristaltic heart tube. Reciprocal changes in the activity-inactivity pattern of the HN (5) cell pair are responsible for the observed spontaneous reciprocal changes in coordination mode. When cell HN (5) is made to be active or inactive, by intracellularly injected current, similar but unilateral changes, in coordination mode occur.
Similar content being viewed by others
References
Ayers, J.L.Jr., Davis, W.J.: Neuronal control of locomotion in the lobster,Homarus americanus. I. Motor programs for forward and backward walking, J. comp. Physiol.115, 1–27 (1977)
Hammersen, F., Staudte, H.W.: Beiträge zum Feinbau der Blutgefäße von Invertebraten. I. Die Ultrastruktur des Sinus Lateralis vonHirudo medicinalis. Z. Zellforsch.100, 215–250 (1969)
Kristan, W.B., Jr., Stent, G.S., Ort, C.A.: Neuronal control of swimming in the medicinal leech. I. Dynamics of the swimming rhythm. J. comp. Physiol.94, 97–119 (1974)
Mann, H.: Leeches. New York: Pergamon Press 1962
Nicholls, J.G., Purves, D.: Monosynaptic chemical and electrical connexions between sensory and motor cells in the central nervous system of the leech. J. Physiol.209, 647–667 (1970)
Thompson, W.J., Stent, G.S.: Neuronal control of heartbeat in the medicinal leech. I. Generation of the vascular constriction rhythm by heart motor neurons. J. comp. Physiol.111, 261–279 (1976a)
Thompson, W.J., Stent, G.S.: Neuronal control of heartbeat in the medicinal leech. II. Intersegmental coordination of heart motor neuron activity by heart interneurons. J. comp. Physiol.111, 281–307 (1976b)
Thompson, W.J., Stent, G.S.: Neuronal control of heartbeat in the medicinal leech. III. Synaptic relations of the heart interneurons. J. comp. Physiol.111, 309–333 (1976c)
Author information
Authors and Affiliations
Additional information
I would like to thank Dr. Gunter Stent for his many helpful discussions and for his help in preparing this manuscript. I would also like to thank Drs. William Kristan Jr. and Wesley Thompson for criticizing the manuscript, and Mrs. Georgia Harper and Mrs. Margery Hoogs for their technical help. Supported by NSF Grant No. GB 31933X and NIH Research Grant No. NS 12813 and NIH Postdoctoral Fellowship No. NS 01222.
Rights and permissions
About this article
Cite this article
Calabrese, R.L. The neural control of alternate heartbeat coordination states in the leech,Hirudo medicinalis . J. Comp. Physiol. 122, 111–143 (1977). https://doi.org/10.1007/BF00611251
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF00611251