Autonomic Nervous System

Question 1

All peripheral autonomic motor pathways consist of how many neurons?

Answer 1

• 2 neurons

Question 2

What is a preganglionic neuron?

Answer 2

• cell body in the brain stem or lateral horn of the spinal cord
• axon (myelinated) exits the CNS as part of a cranial nerve or anterior root of a spinal nerve and carries signals to a peripheral ganglion

Question 3

What is a postganglionic neuron in the autonomic motor pathways?

Answer 3

• cell body in a peripheral ganglion

- axon (unmyelinated) carries signals to an effector

Question 4

Where do preganglionic neurons originate in the autonomic motor pathways?

Answer 4

• in the lateral horns of the
  T1-L2 spinal cord segments
• white matter

Question 5

Where do postganglionic neurons originate?

Answer 5

• in peripheral ganglia:
• sympathetic trunk (chain) ganglia
• prevertebral ganglia
• grey matter

Question 6

What are sympathetic trunk (chain) ganglia?

Answer 6

• form chains that run along either side of the vertebral column
• generally innervate viscera above the diaphragm

Question 7

What are prevertebral ganglia?

Answer 7

• lie close to large arteries in the abdominal cavity

- generally innervate viscera below the diaphragm

Question 8

When pre-ganglionic neurons enter a sympathetic trunk ganglion, what can they do?

Answer 8

• synapse in the ganglion
• travel up (cervical) or down (lumbar/sacral/coccygeal) the sympathetic trunk and
  synapse at another sympathetic trunk ganglion
• pass through the sympathetic trunk ganglion without synapsing and travel to a
  prevertebral ganglion (where they synapse)

Question 9

Post-ganglionic neurons that originate in the sympathetic trunk generally innervate what?

Answer 9

• viscera above the diaphragm

Question 10

Post-ganglionic neurons that originate in the prevertebral ganglia generally innervate what?

Answer 10

• viscera below the diaphragm

Question 11

Where do the preganglionic neurons originate in the parasympathetic nervous system?

Answer 11

• brain stem and lateral horns of the S2-S4 spinal cord segments
• brain stem (CNs) – innervate the viscera of the head (CNs III, VII, IX) as
  well as the thoracic cavity and most of the abdominal cavity (CN X)
• S2-S4 segments – innervates part of the large intestine as well as the
  pelvic viscera

Question 12

Where do the postganglionic neurons originate in the parasympathetic nervous system?

Answer 12

• “terminal” ganglia

that are located close to or within the visceral organs

Question 13

Which area of the brain regulates the balance between the

sympathetic and parasympathetic nervous systems?

Answer 13

• the hypothalamus