Question

Which of the following is a difference between the sympathetic and parasympathetic nervous systems?

- Norepinephrine is released exclusively from post ganglionic fibers in the sympathetic system.

- The adrenal gland enhances responses from the parasympathetic system.

- The sympathetic system nerves exit the spinal cord in the cervical region of the vertebral column.

- Postganglionic fibers are longer in the parasympathetic system.

- All of these are differences in the autonomic nervous system.

Answer 1

Answer: (A) Norepinephrine is released exclusively from post ganglionic fibers in the sympathetic system.

Bith sympathetic and parasympathetic preganglionic fibers release ACh. The receptor for postganglionic parasympathetic fibers which also release ACh are muscarinic receptors. But the postganglionic sympathetic fibers release norepinephrine except few swear glands and blood vessels.

The sympathetic neuron exit via spinal nerves of lumbar/thoracic regions of the spinal cord. By comparing the lengths, the parasympathetic preganglionic fibers are relatively long and postganglionic fibers are short this is because that the target effectors are close to ganglia.