Parasympathetic Versus Sympathetic, Essay Example

The autonomic nervous system uses preganglionic neurons to connect ganglion to the central nervous system.  The autonomic nervous system, ANS, is classified into two subdivisions, the parasympathetic nervous system (PSNS) and the sympathetic nervous system (SNS). The two divisions usually oppositely complement each other like to parts of a puzzle, in order to achieve homeostasis in functions and to accomplish one responsive action.  The sympathetic division is also recognized as the part of the nervous system that is involved in fight or flight responses. Contrary to the sympathetic, the parasympathetic division does not require instantaneous reactions to a stimuli. Instead, a parasympathetic response has time to consider consequences of reactions before responding, in other words, a rest and digest response.

The SNS is involved in many physiological functions including directing blood flow away from the gastrointestinal tract and the skin by using vasoconstriction, improving blood flow to the skeletal musculature and the lungs, dilating the bronchioles of the lungs which allows for improved oxygen exchange, and increasing the rate of the heart.  PSNS normally functions in contrasted ways to the SNS by dilating blood vessels leading to the GI tract, allowing closer vision by constricting the pupil and contracting the ciliary muscles to the lens, and stimulating salivary production.

Both divisions originate from the spinal cord, however the PSNS is mainly distinguished in the medulla while the SNS is most originated in the thoracic and lumbar of the spinal cord. There is also a difference in the neuron pathways between both divisions.  The nerve pathway of the PSNS is longer and slower when compared to the pathway of the SNS which has very short neurons that operate in a faster system. In addition, the main jobs of each division is different. The job of the PSNS is to restore the body to a state of calmness after the SNS has tensed the body to bring about alertness during a perceived threat.