Autonomic Nervous System

Question 0

What is meant by a two neuron system of the ANS?

Answer 0

it takes 2 neurons to link the target organ to the CNS

Question 1

What are the two divisions of the autonomic nervous system?
What are their general functions?

Answer 1

The sympathetic (stimulatory) and parasympathetic (inhibitory).

Question 2

How is this two neuron system constructed?

Answer 2

A preganglionic fiber leaves the CNS and extends to a ganglion where it synapses on the cell body of the postganglionic neuron. the postganglionic fiber extends from the ganglion to the target

Question 3

Where are the neuron cell bodies of origin for the each division of the ANS located? Based on this location, what are the anatomical-based names for each division?

Answer 3

sympathetic- intermediolateral gray horn of spinal levels T1-L2, thoracolumbar
parasympathetic- brain stem and spinal levels S2-S4, craniosacral

Question 4

Which 2 of the 3 types of autonomic ganglia are associated with the sympathetic synapse in the ANS.

Answer 4

sympathetic fibers synapse in the paravertebral (sympathetic trunk) and prevertebral (collateral) autonomic ganglia

Question 5

What are the three types of prevertebral ganglia?

Answer 5

Celiac, superior mesenteric, and inferior mesenteric ganglia

Question 6

Which type of autonomic ganglia is strictly involved in the parasympathetic synapse?

Answer 6

the intramural (terminal) autonomic ganglion.

Question 7

where is each of the 3 autonomic ganglia found?

Answer 7

paravertebral- in a chain along either side of the vertebral column
prevertebral- anterior to the vertebral column at the base of the 3 main abdominal arteries arising from the aorta
intramural- within the wall of the target organ

Question 8

Understand the functional arrangement of the fibers within the sympathetic NS.

Answer 8

The body wall (somatic division) can only be supplied by postganglionic sympathetic innervation. The preganglionic fibers leaving the CNS via the ventral root must find an ANS ganglion in which to synapse prior to innervating the body wall.

Question 9

What is the function of the sympathetic trunk?

Answer 9

• it provides a site for the pre/postganglionic synapse for sympathetic innervation to the body wall
• it distributes sympathetic innervation above T1 and below L2 ( where there are no sympathetic neuron cell bodies) as the entire body wall must receive sympathetic innervation.

Question 10

How do white and gray rami communicans differ?

Answer 10

White rami contain preganglionic sympathetic fibers and visceral afferent fibers, both of which are myelinated.
Gray rami contain postganglionic sympathetic fibers, no myelin.

Question 11

What is the function of each ramus communicans?

Answer 11

White rami convey myelinated preganglionic sympathetic fibers from the ventral ramus of the spinal nerve to the paravertebral (sympathetic) ganglion.
Gray ramus conveys the unmyelinated postganglionic sympathetic fibers from the ganglion back to the ventral ramus for distribution through the dorsal and ventral rami to supply the entire dermatome with sympathetic innervation.

Question 12

Which is more numerous rami and why?

Answer 12

Gray rami are more numerous. White rami are only present at vertebral levels where there is sympathetic input to the sympathetic trunk (T1-L2). Gray rami output from the sympathetic trunk to all levels along the sympathetic trunk (C1 to Co4) as the entire body wall has to receive sympathetic innervation.

Question 13

What is a splanchnic nerve?

Answer 13

A fiber that arises from the sympathetic trunk and passes medially to a prevertebral ganglion

Question 14

What fiber types does a splanchnic nerve contain?

Answer 14

primarily preganglionic sympathetic fibers destined for the viscera, but sometimes postganglionic sympathetic, preganglionic parasympathetic fibers as well.

Question 15

List the autonomic ganglia of the head associated with the parasympathetic division of the ANS.

Answer 15

Cillary, submandibular, pterygopalatine, and otic autonomic ganglia. Only parasympathetic fibers synapse here. THE GANGIA ARE NOT IN THE BODY WALL

Question 16

With which cranial nerve is each associated?

Answer 16

Cillary ganglion: CN III (oculomotor)
Submandibular ganglion: CN VII (facial)
Pterygopalatine ganglion: CN VII (facial)
Otic ganglion: CN IX (glossopharyngeal)

Question 17

Which cranial nerve is responsible for the majority of the parasympathetic supply to the viscera of the thorax and abdomen?

Answer 17

CN X (vagus)

Question 18

Which ganglion type is involved in the parasympathetic innervation of the thorax and abdomen?

Answer 18

Intramural (terminal) parasympathetic ganglia

Question 19

How far distal does the vagus nerve innervation extend into the abdomen?

Answer 19

The vagus nerve supplies parasympathetic innervation through the abdomen as far distally as the mid transverse colon

Question 20

What takes over once the vagal innervation terminates?

Answer 20

From the mid transverse colon down into the pelvis, parasympathetic innervation arises from S2-S4.

Question 21

Generalize the differences between the two divisions of the ANS made obvious by the summary diagram: origin, fiber lengths, and ganglia used for synapse.

Answer 21

Origin: Symp- T1-L2 Para- brain stem & S2-S4
Fiber lengths: symp- short preganglionics and long postganglionics. Para- long preganglionics, short postganglionics.
Ganglia used for synapse: symp- paravertebral and prevertebral. Para- intramural/terminal

Question 22

Name the 3 prevertebral ganglia of the abdomen. Which fibers of the ANS synapse here?

Answer 22

Celiac, Superior Mesenteric, Inferior Mesenteric.
Preganglionic sympathetic fibers synapse here, preganglionic parasympathetic fibers pass through these ganglia to synapse in the intramural ganglia of the target organs.

Question 23

_____ rami input ______ impulse into the _____ ______ from T1-L2

Answer 23

White ; sympathetic ; sympathetic trunk

Question 24

Three things that can happen to preganglionic sympathetic fiber once in sympathetic trunk

Answer 24

1) synapse in the paravertebral ganglion, then Post Gang. fiber re-enters ventral/dorsal rami via grey ramus communicans to body wall.
2) synapse in paravertebral ganglion @ level other than it entered, Post Gang. re-enters the ventral/dorsal rami via grey ramus comm. to body wall or visceral
3) passes through paravertebral ganglion via splanchnic nerve to a prevertebral autonomic ganglion where it synapses. the Post Gang. then goes to target organ (usually a visceral organ)

Question 25

___ rami are found at every vertebral level that exhibits a sympathetic ganglion. ___ ____ _____ are output fibers for the sympathetic division of the ANS

Answer 25

Gray rami ; gray rami communicans

Question 26

Are there more gray or white rami? Why?

Answer 26

Gray ; white rami input sympathetic innervation so that is restricted to T1-L2 where the sympathetic cell bodies are located,

Question 27

Preganglionic parasympathetic fibers travel out via _______ from the brain stem and ________ from the sacral cord levels.

Answer 27

cranial nerves ; pelvic splanchnic nerves

Question 28

What types of fibers can cranial nerves contain?

Answer 28

NEVER SYMPATHETIC– only motor, sensory, and parasympathetic

Question 29

Is there sympathetic innervation in the brain?

Answer 29

NOOOOOO

Question 30

Why do parasympathetic fibers have a long preganglion fiber?

Answer 30

To travel into the wall of the organ to synapse at the intramural ganglion.

Question 31

What is the purpose of the sympathetic trunk?

Answer 31

Distribute sympathetic innervation below L2 & above T1.

Question 32

Only _____ fibers supply body wall

Answer 32

Postganglionic sympathetic fibers (why!??!)

Question 33

What modalities contained in posterior/anterior rami?

Answer 33

postganglionic sympathetic
somatic motor
somatic sensory