Anatomy of the ANS week 3 Flashcards Preview

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Flashcards in Anatomy of the ANS week 3 Deck (12)
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What divisions of the nervous system is the ANS found? (CNS, PNS, both)

The ANS is located both within the CNS and PNS


What are GVA and GVE fibers? 

GVA: sensory nerves monitoring changes in viscera (organs) and bringing that info to the CNS. This info travels with somatic components to assist in regulation of the heart, respiration, etc.

GVE: motor nerves prodiving innervation mainly to smooth muscle, cardiac muscle, and glands. Fibers have their origins in the CNS


GVE are organized into a two neuron chain. What does this mean? Why are GVA neurons not classified as sympathetic or parasympathetic?

The preganglionic cell bodies of both sympathetic and parasympathetic neurons reside in the CNS (just in different parts) and the postganglionic fibers of both of these branches reside in the PNS. The target is viscera (smooth muscle, cardiac muscle, gland).

GVA is just sensory input. It is GVE innervation that is classified as sympathetic or parasympathetic.


What are lateral (paravertebral), collateral (prevertebral) and terminal ganglia? Where are they located and what kinds of fibers do they contain?

Note that these ganglia are NOT dorsal root ganglia! The DRG is purely afferent so it also has GVA fibers but no GVE. This makes sense bc you would not have efferent fibers in the DRG.

lateral (paravertebral ganglia): paired structrues alongside the vertebral column (sympathetic trunk). contain postganglionic sympathetic fibers. 

Collateral (Prevertebral) Ganglia: Structures located anterior to the vertebral column in the abdomen. bc they are located in the abdomen, we will not see them but must know them conceptually. they contain postganglionic sympathetic neurons

Terminal Ganglia: These structures are found in or near the walls of organs and cannot be observed grossly due to their small size. E.g. such ganglia would be found in the cardiac or pulmonary plexuses. parasympathetic postganglionic fibers. parasympathetic use terminal ganglia. are short bc they are near organs


Where in the spinal cord are sympathetic cell bodies located? Where are the sites of synapse (postganglia)? What do they innervate? At what levels of the spinal cord are thoracic and lumbar splanchnic nerves located? What do they innervate?

The sympathetic NS is described as thoraco-lumbar. Note that the sympathetic chain extends from the base of the skull to the coccyx but the cell bodies of preganglionic sympathetic fibers are only found btwn T5 and L2. Also note we are not responsible for the specific names of the prevertebral ganglia.


Where do the cell bodies of preganglionic parasympathetic neurons reside? Where do they synapse? What do they innervate? What is the main parasympathetic nerve we are responsible for at this time? 

The parasympathetic nervous system is cranio-sacral in origin. Cell bodies reside in the brainstem and are sent out by cranial nerves or reside in the sacral spinal cord. 

Note that the vagus nerve is the part of the parasympathetic NS we are responsible for at this time bc it innervates thoracic viscera. The vagus nerve only contains the fibers of preganglionic neurons (no cell bodies bc nerves do not contain cell bodies). 


How are the plexuses of thoracic viscera (cardiac, esophageal plexuses) formed? 

The preganglionic fibers of the vagus nerve and postganglionic fibers of the sympathetic chain merge to form these plexuses to provide sympathetic and parasympathetic innervation to these organs. 


What are the 2 ways in which a sympathetic preganglionic neuron can travel to synapse in the sympathetic chain? Where does the postganglionic neuron travel?

Option 1:

A sympathetic preganglionic neuron can travel out of the spinal cord, ventral root, through a spinal nerve, through a ventral ramus, and through a white rami communicans to synapse on a postganlionic neuron in the sympathetic chain at the same level of the spinal cord from where it exited.

Option 2:

A sympathetic preganglionic neuron can travel upward or downward through the sympathetic chain to synapse on a postganglionic neuron that is not at the same level of the spinal cord from where it exited. (It would still first travel through a ventral root, a spinal nerve, a ventral ramus, and white rami communicans first at the same level from where it exited). This is what creates the sympathetic chain itself and is the reason that the sympathetic chain extends from the head to the coccyx although the cell bodies are only in T5-L2. 

After being synapsed on by a preganglionic nerve, the postganglionic nerve travels through a gray rami communicans and out through either a dorsal or ventral ramus to innervate its target. Note that postganglionic neurons always exit the spinal cord at the same level at which they originated. 




Are splanhcnic nerves pre or post ganglionic? Where do they come from? What do they innervate? How do they travel?

Splanchnic nerves are preganglionic neurons that pass through the sympathetic chain (at T5-L2) to innervate abdominal viscera. They do not innervate thoracic viscera! These nerves pass through the ventral root, spinal nerve, ventral ramus, and white rami communicans before exiting the sympathetic chain. These nerves sit anterior to the vertebral column (prevertebral) and do not synpase until they get to their targets in the abdomen. 


Describe the innervation of the heart.

The heart receives parasympathetic innervation from the vagus nerve (SA and AV nodes, atria) and sympathetic innervation (SA and AV nodes, atria, ventricles). Postganglionic sympathetic nerves do not pass through the ventral ramus. Instead, they branch directly from the sympathetic trunk at levels T1-T4 to innervate the heart. The parasympathetic and sympathetic fibers converge to form the cardiac plexus. see slide 15 of notes!


Each spinal nerve receives _____ rami communicans.

gray. makes sense because gray rami communicans are the means through which postganglionic fibers pass to innervate viscera of the entire body


_____ rami communicans exist from T1-L2 only. 

white. makes sense because white rami communicans are the means by which preganglionic fibers travel to synapse on postganglionic fibers in the sympatehtic chain.