Sympathetic and Parasympathetic Divisions The autonomic nervous system is made up of two divisions, the Sympathetic and Parasympathetic. There are many differences between these divisions. First of all there are anatomical and physiological differences. The parasympathetic division of the autonomic nervous system originates from the craniosacral out flow, which is the brain stem nuclei of cranial nerves III, VII, IX, and X; and spinal cord segments S2-S4. The sympathetic division on the other hand is much more complex than the parasympathetic and its origin is in the thoracolumbar out flow that is in the gray matter of the spinal cord segments thoracic I to lumbar 2 vertebrae. Another important physiological difference is the location of ganglia in each division. Ganglia of the parasympathetic division are in intramural or close to the visceral organ served. The sympathetic ganglia on the other hand are located within centimeters of the central nervous system; furthermore, the ganglia are also alongside the vertebral column and anterior to the vertebral column. The relative length of preganglionic and postganglionic fibers in the parasympathetic and sympathetic division is also dissimilar. The parasympathetic division has long preganglionic and short postganglionic fibers; whereas, the sympathetic are just the opposite, short preganglionic and long postganglionic fibers. There is no rami communication in the parasympathetic division, while the sympathetic division has gray and white rami communication. The functional goal of the parasympathetic division is maintenance, which is to conserve and store energy. The sympathetic divisions goal is to allow the body to cope with emergencies and intense muscular activity. There are many effects of the parasympathetic and sympathetic divisions on various organs. The constriction of muscles in the eye pupil stimulates the iris by the parasympathetic system. The sympathetic effects are the stimulation of dilator muscles and dilate the eye pupils. Parasympathetic effects of the cilliary muscle of the eye are to stimulate muscles, which result in the bulging of the lens for accommodation and close vision. There are no effects from the sympathetic division.

Both divisions effect the nasal lacrimal, salivary, gastric, and pancreas glands. The parasympathetic division stimulates secretory activity, where the sympathetic division inhibits secretory activity and causes vasoconstriction of blood vessels supplying the glands. There is no parasympathetic effect on sweat glands, the adrenal medulla, or the arrector pili muscles. There are sympatheic effects that cause secretory activity to be inhibited therefore causing vasoconstriction of blood vessels supplying the glands. The parasympathetic division decreases the rate of the heart and slows it down. The sympathetic division increases the rate and the force of the heartbeat. Bladder activity is also the opposite in both divisions. In the parasympathetic of the bladder, contraction of smooth muscle occurs, on the other hand, relaxation of smooth muscle occurs in the sympathetic division. The sympathetic division has a great effect on the body s liver; it causes an epinephrine stimuli, which causes the release of glucose to the blood. There is no parasympathetic effect on the liver. In the parasympathetic division the gall bladder contracts, causing bile to expel, whereas, the gall bladder is relaxed in the sympathetic division. The parasympathetic and sympathetic divisions also have effects on the human reproductive organs. The parasympathetic division causes the penis and vagina to vasodialate or become erect. The sympathetic division causes the penis to ejaculate and the vagina contract. There is little or no effect of the blood vessels in the parasympathetic division. The sympathetic division constricts most vessels and increases the blood pressure. It also constricts vessels of the abdominal viscera and skin to divert blood to muscles, brain, and heart when necessary. Together these two divisions play an important role in our daily lives. These processes continuously work, along with our central nervous system, to maintain normal body functions. These divisions allow us to conduct our lives without the worry of conscience thought. Without these two divisions our lives would be in total chaos. The human body is a wondrous thing; just imagine all the things we take for granted.