A neuroanatomical and electrophysiological analysis of nervous regulation in the heart of an isopod crustacean,Bathynomus doederleini

Abstract

1. We have used anatomical, histological, and electrophysiological techniques to study the innervation of the heart of an isopod,Bathynomus doederleini. 2. The heart beat was driven by a cardiac ganglion consisting of twelve morphologically identical neurones. 3. The paired anterior cardiac nerves each contained five axons: three cardio-regulator axons, and two motor axons to anterior cardio-arterial valves. 4. The functions of the cardio-regulator axons were elucidated by stimulating individually one inhibitor and two accelerator axons on either side. 5. The two cardio-accelerator axons (on each side) were functionally identical. They innervated the cardiac ganglion, producing discrete EPSPs. 6. The cardio-inhibitor axon induced discrete IPSPs in the cardiac ganglion. This axon may also directly innervate the myocardium. 7. The two pairs of valve motor nerves each contained one excitor axon and one inhibitor axon. The excitatory innervation produced valve contraction resulting in a decrease of arterial dilation during systole. The inhibitory innervation produced valve relaxation resulting in an increase of arterial dilation. 8. The valve axons may regulate the distribution of haemolymph among arteries. The cardiac output may be regulated by the nerves to the cardio-arterial valves and the cardio-regulator nerves to the heart.