Autonomic Nervous System Flashcards
What is meant by a two neuron system of the ANS?
it takes 2 neurons to link the target organ to the CNS
What are the two divisions of the autonomic nervous system?
What are their general functions?
The sympathetic (stimulatory) and parasympathetic (inhibitory).
How is this two neuron system constructed?
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
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?
sympathetic- intermediolateral gray horn of spinal levels T1-L2, thoracolumbar
parasympathetic- brain stem and spinal levels S2-S4, craniosacral
Which 2 of the 3 types of autonomic ganglia are associated with the sympathetic synapse in the ANS.
sympathetic fibers synapse in the paravertebral (sympathetic trunk) and prevertebral (collateral) autonomic ganglia
What are the three types of prevertebral ganglia?
Celiac, superior mesenteric, and inferior mesenteric ganglia
Which type of autonomic ganglia is strictly involved in the parasympathetic synapse?
the intramural (terminal) autonomic ganglion.
where is each of the 3 autonomic ganglia found?
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
Understand the functional arrangement of the fibers within the sympathetic NS.
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.
What is the function of the sympathetic trunk?
- 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.
How do white and gray rami communicans differ?
White rami contain preganglionic sympathetic fibers and visceral afferent fibers, both of which are myelinated.
Gray rami contain postganglionic sympathetic fibers, no myelin.
What is the function of each ramus communicans?
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.
Which is more numerous rami and why?
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.
What is a splanchnic nerve?
A fiber that arises from the sympathetic trunk and passes medially to a prevertebral ganglion
What fiber types does a splanchnic nerve contain?
primarily preganglionic sympathetic fibers destined for the viscera, but sometimes postganglionic sympathetic, preganglionic parasympathetic fibers as well.
List the autonomic ganglia of the head associated with the parasympathetic division of the ANS.
Cillary, submandibular, pterygopalatine, and otic autonomic ganglia. Only parasympathetic fibers synapse here. THE GANGIA ARE NOT IN THE BODY WALL
With which cranial nerve is each associated?
Cillary ganglion: CN III (oculomotor)
Submandibular ganglion: CN VII (facial)
Pterygopalatine ganglion: CN VII (facial)
Otic ganglion: CN IX (glossopharyngeal)
Which cranial nerve is responsible for the majority of the parasympathetic supply to the viscera of the thorax and abdomen?
CN X (vagus)
Which ganglion type is involved in the parasympathetic innervation of the thorax and abdomen?
Intramural (terminal) parasympathetic ganglia
How far distal does the vagus nerve innervation extend into the abdomen?
The vagus nerve supplies parasympathetic innervation through the abdomen as far distally as the mid transverse colon
What takes over once the vagal innervation terminates?
From the mid transverse colon down into the pelvis, parasympathetic innervation arises from S2-S4.
Generalize the differences between the two divisions of the ANS made obvious by the summary diagram: origin, fiber lengths, and ganglia used for synapse.
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
Name the 3 prevertebral ganglia of the abdomen. Which fibers of the ANS synapse here?
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.
_____ rami input ______ impulse into the _____ ______ from T1-L2
White ; sympathetic ; sympathetic trunk
Three things that can happen to preganglionic sympathetic fiber once in sympathetic trunk
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)
___ rami are found at every vertebral level that exhibits a sympathetic ganglion. ___ ____ _____ are output fibers for the sympathetic division of the ANS
Gray rami ; gray rami communicans
Are there more gray or white rami? Why?
Gray ; white rami input sympathetic innervation so that is restricted to T1-L2 where the sympathetic cell bodies are located,
Preganglionic parasympathetic fibers travel out via _______ from the brain stem and ________ from the sacral cord levels.
cranial nerves ; pelvic splanchnic nerves
What types of fibers can cranial nerves contain?
NEVER SYMPATHETIC– only motor, sensory, and parasympathetic
Is there sympathetic innervation in the brain?
NOOOOOO
Why do parasympathetic fibers have a long preganglion fiber?
To travel into the wall of the organ to synapse at the intramural ganglion.
What is the purpose of the sympathetic trunk?
Distribute sympathetic innervation below L2 & above T1.
Only _____ fibers supply body wall
Postganglionic sympathetic fibers (why!??!)
What modalities contained in posterior/anterior rami?
postganglionic sympathetic
somatic motor
somatic sensory
