Complete each sentence by dragging a word to the proper position. Then arrange the sentences into the order of occurrence of motor impulses in the ANS This parasympathetic neurotransmitter causes a in heart rate and contractility Action potentials arriving at the sinoatrial and atrioventricular nodes of the heart cause to be released. Also known as the division, the parasympathetic nervous system has fibers exiting the CNS at the medulla oblongata. Action potentials travel down the preganglionic nerve fibers of the towards the effector organs. The impulse arrives relatively quickly at the heart, as parasympathetic postganglionic fibers are compared to sympathetic postganglionic fibers. These impulses arrive at the cardiac plexus where secretion of acetychline creates an action potential in the neuron.