Question

Why does blocking the parasympathetic nervous system stimulates the sympathetic nervous system?

Answer 1

The autonomic nervous system have two subtypes called sympathetic nervous system and parasympathetic nervous system. The balance between these two nervous system keeps the automated body functions working properly.

• The symapthetic nervous system originates from the thoracic and lumbar region of the spinal cord. Norepinephrine is the major neurotransmitter released by the post ganglionic sympathetic nervous system. A small amount of epinehrine is released by the sympathetic neurons of the adrenal medulla. This receptors are responsible for the fight and flight response in the body.
• The parasympathetic nervous system originates from the cervical or sacral region of the spinal cord. Acetylcholine is the major neurotransmitter released by the postganglionic parasympathetic nervous system. It stimulates the muscarinic receptors expressed on target organs.

These two types of autonomic nervous system have opposite effect on a given tissue increasing the activity of one system while simultaneously decreasing the activity of other system. Through this actions of sympathetic and parasymapthetic nervous system, the body maintains the hemostasis. This is the reason why blocking the parasympathetic nervous system stimulates the sympathetic nervous system Each system is dominant under certain conditions. The sympathetic system predominates during emergency 'fight or flight 'reaction and during exercise.It prepares the body for the strenous activity by increasing the flow of the oxygenated blood to the tissues especially skeletal muscles. The parasympathetic system predominates during the resting and quiet conditions.In these condition it conserves and stores the energy and to regulate basic body function like digestion and urination.