Which system has more divergence of preganglionic axons?
Multiple Choice
Parasympathetic division
Sympathetic division
The correct answer and explanation is:
The correct answer is Sympathetic division.
The sympathetic division of the autonomic nervous system (ANS) exhibits greater divergence of preganglionic axons compared to the parasympathetic division. This divergence refers to the number of postganglionic neurons that a single preganglionic axon synapses with.
In the sympathetic division, preganglionic neurons originate in the thoracolumbar region (T1-L2) of the spinal cord. These preganglionic axons are relatively short and synapse in the sympathetic ganglia, which are located near the spinal cord. The postganglionic neurons, which are longer, can then send signals to a large number of organs and tissues, often reaching distant parts of the body. This system is highly divergent, with a single preganglionic neuron typically synapsing with multiple postganglionic neurons. This large-scale divergence allows the sympathetic division to initiate a widespread “fight or flight” response, affecting multiple organs simultaneously.
On the other hand, the parasympathetic division, which primarily operates through craniosacral pathways (with preganglionic neurons originating in the brainstem and sacral spinal cord), has less divergence. Preganglionic axons are longer, and they synapse with fewer postganglionic neurons, often in or near the target organs. The parasympathetic division primarily serves more localized functions, such as promoting rest, digestion, and energy conservation, through the “rest and digest” response.
This difference in the degree of divergence between the two systems is tied to their respective physiological roles. The sympathetic division needs to rapidly mobilize resources and coordinate a whole-body response in times of stress, while the parasympathetic division is more focused on maintaining homeostasis and supporting specific bodily functions.