ANS Learning Objectives

Question 1

What are the 2 divisions of the autonomic nervous system and what are their general functions?

Answer 1

• sympathetic: fight or flight
• parasympathetic: rest and digest

Question 2

How many neurons link the CNS to the target for the ANS system? What do ANS neurons innervate?

Answer 2

• 2 neurons: preganglionic (grey matter of lateral horn) and postganglionic (cell body outside CNS in autonomic ganglia)
• Smooth muscle, glands, modified cardiac muscle, SA and AV nodes

Question 3

Sympathetics: origin, fiber lengths, and targets

Answer 3

Origin: T1-L2
FL: Pre = short and Post = long
Ganglia: para and pre vertebral
Targets: everywhere

Question 4

Parasympathetics: origin, fiber lengths, and targets

Answer 4

Origin: CN nuclei and S2-S4
FL: Pre = long and Post = short
Ganglia: intramural
Targets: head and organs; NO body wall or limbs

Question 5

Which ANS system does not target structures in the body wall?

Answer 5

Parasympathetic

Question 6

Where are the cell bodies of origin (preganglionic) for the sympathetic system located?

Answer 6

• T1-L2/3
• IML (in 3D)
• Lateral horn from T1-L2/3 (in cross section)

Question 7

Be able to describe the somatotopic organization of the IML (head, upper limb, thoracic cavity viscera)

Answer 7

T1-T6

Question 8

Be able to describe the somatotopic organization of the IML (trunk body wall)

Answer 8

T1-L1

Question 9

Be able to describe the somatotopic organization of the IML (lower limb)

Answer 9

T12-L2/3

Question 10

Be able to describe the somatotopic organization of the IML (abdominopelvic viscera)

Answer 10

T5-L2/3

Question 11

Where are paravertebral (sympathetic) autonomic ganglia found? Which ganglia are associated with targets in upper limb and body wall?

Answer 11

• on either side of vertebral column
• ONLY sympathetic
• smooth muscle, arteries and glands in body wall
• thoracic cavity viscera
• head

Question 12

Where are prevertebral (sympathetic) autonomic ganglia found? Which ganglia are associated with targets in upper limb and body wall?

Answer 12

• in front of vertebral column, close to abdominal artery
• ONLY sympathetic
• abdominal and pelvic cavity viscera

Question 13

Why does the sympathetic trunk exist? What is its function?

Answer 13

• Paired structure lying on either side of the vertebral column
• Composed of paravertebral ganglia
• Distributes postganglionic sympathetic innervation throughout the body

Question 14

How do white and gray rami communicans differ? What is the function of each ramus communicans? Which vertebral levels do you find each of the ramus communicans?

Answer 14

White: Only for T1-L2/3, exit spinal n close to branching point of ventral and dorsal rami, only route preganglionic sympathetic fibers can take to get to sympathetic trunk

Grey: All 31 spinal levels, extends from paravertebral ganglia to spinal n, only route back out to spinal n from sympathetic trunk

Question 15

How does sympathetic supply to the body wall differ from sympathetic innervation to the body cavities & head neck? What nerve structures are utilized to deliver sympathetic innervation to these areas from the sympathetic trunk?

Answer 15

• T1-L2/3: synapse at same level they entered
• Inferior to L2/3: descend in sympathetic trunk then synapse
• Superior to T1: ascend in sympathetic trunk then synapse
• Abdomen or pelvis: leave synaptic trunk w/o synapsing (referred to as splanchnic)

Question 16

Routes that a preganglionic sympathetic fiber can take from the entry point into the sympathetic trunk:

Answer 16