Question

The pregangliotic fibers of the parasympathetic nervous system emerge from

a. thoracolumbar spinal region

b. sympathetic chain

c. higher brain centers

d. brain stem and sacral region of spinal cord

Answer 1

Question.

The preganglionic fibers of the parasympathetic nervous system emerge from:

Answer: d) brain stem and sacral region of spinal cord.

Explanation: Autonomic nervous system is a part of peripheral nervous system that regulates the activities of internal organs like gastrointestinal tract, heart, blood vessels, genitourinary system, lungs, pupils, etc. These activities are involuntary and unconsciously regulated. Autonomic nervous system is divided into two parts namely sympathetic nervous system and parasympathetic nervous system.

Parasympathetic nervous system basically regulates the activities of "rest and digestion". Its preganglionic nerve fibers arises from the midbrain part of brain stem and sacral region of the spinal cord. Hence, it forms the cranio-sacral outflow. It's ganglions are located close to the organs and the post-ganglionic fibers release acetylcholine as the neurotransmitter hence its nerves are cholinergic nerves. It's pre-ganglionic fibers are long and post-ganglionic fibers are short.

Sympathetic nervous system is concerned with the function of "fight and flight" response of the body. It's pre-ganglionic fibers originate from the thoracic and lumbar segments of the spinal cord hence it forms the thoraco-lumbar outflow. It's ganglions are located on either side of the spinal cord as sympathetic chains. Thus, it's pre-ganglionic fibers are short and post-ganglionic fibers are long. It's post-ganglionic fibers release nor-adrenaline or adrenaline hence its also called as adrenergic system.