Physiology

Abstract

Marine animals have contributed significantly to the development of the studies of general and comparative physiology. Experiments on nerve excitation in squids, muscle contraction in bivalves, and heart function in octopus and tunicates are introduced in this chapter. Squids have a giant axon, which enables effective ejection of water from the mantle upon jet propulsion. The giant axon can be isolated to measure the conduction velocity of action potential. Bivalves have catch muscle, which exerts force almost without energy expenditure while attached to rocks. Catch muscle can be prepared with or without nerve to induce contraction by applying electrical stimuli or neurotransmitter. Hearts in octopus and tunicates modulate output by controlling the heart rate and the blood flow direction, respectively. Hydrostatic pressure can be applied to isolated octopus heart and examine how the heart rate is affected by the blood pressure. It is also possible to induce and observe reversals of the blood flow in tunicate tubular hearts.