So once again, in the case of the sympathetic nervous system, every single pre ganglionic cell begins in our spinal cord and we'll see this is not the case in the parasympathetic system. Now, there is an exception to this rule. So inside the sympathetic nervous system, we usually have two of these neurons. We have a pre and opposed ganglionic neuron. But there is one exception. The electrical signal that is carried from the spinal cord to our adrenal medulla is carried by only a single neuron, by one pre ganglionic neuron.