They constrict because our rate of activity decreases inside the gastrointestinal system. So now that we know what the job and function of the sympathetic nervous system is let's actually discuss the pathway of the electrical signal along the neurons inside the sympathetic nervous system. So we have two neurons in our pathway. The first neuron is known as our pre ganglionic neuron and the second neuron is known as the post ganglionic neuron. Now, all pre ganglionic neurons in a sympathetic nervous system begin in the spinal cord of our body. So the cell, body and the dendrites of the pre ganglionic neuron are found in our spinal cord when they actually exit.