Flashcards in Introduction to the Autonomic Nervous System Deck (25)
What is the exception to the "sympathetic = norepinephrine, parasympathetic = acetylcholine" rule?
Sweat glands of the skin are innervated by sympathetic fibers which release acetylcholine
Activation of which system (sympathetic or parasympathetic) leads to widespread and long-lasting effects?
Where are the cell bodies of preganglionic neurons? Postganglionic neurons?
Preganglionic: In the brainstem or spinal cord
Postganglionic: outside of the CNS; collection of nerve bodies is a ganglion.
Describe the myelination of pre and post ganglionic fibers and the neurotransmitters they release in both sympathetic and parasympathetic systems.
Preganglionic fibers of both systems are myelinated and release acetylcholine at terminals
Postganglionic fibers of both systems are unmyelinated and release either norepipneprhine or acetylcholine
Where in the spinal cord are the cell bodies of the sympathetic preganglionic neurons? Which spinal cord segments are these bodies located within?
In the lateral gray horn of the spinal cord; from T1 to L2/L3
Which roots of the spinal cord do preganglionic fibers travel out of, and where do they travel to?
They travel out of the ventral horn, enter the ventral ramus of a spinal nerve
What is the white communicating ramus?
A bundle of myelinated preganglionic fibers exiting the ventral ramus to enter the sympathetic trunk
What is the ganglion at the tip of the coccyx?
On a single trunk, how many:
Cervical: 3 (superior, middle, inferior)
Thoracic: 11 or 12
Lumbar: 4 or 5
Sacrococcygeal: 5 or fewer
What is the fusing of the inferior cervical ganglion and the first thoracic ganglion?
The stellate ganglion
What are the 4 paths that a preganglionic fiber originating in the thoracolumbar portions of the spinal cord can take?
1. Synapse in corresponding ganglia at that level. Postganglionic fibers rejoin spinal nerve via gray communicating ramus
2. Ascend or descend the trunk and synapse at a different level. This is the source of preganglionic fibers for ganglia above T1 or below T2.
3. Pass through sympathetic trunk without synapsing and travel via thoracic, lumbar, and sacral splanchnic nerves to collateral ganglia.
4. Pass through all ganglia (paravertebral and prevertebral) and synapse with chromaffin cells of the adrenal medulla
How do preganglionic sympathetic fibers that innervate the head, neck, body wall, limbs, and thoracic cavity course through?
Either synapse in corresponding ganglia at that level or ascend/descend the trunk and synapse at a different level
How do preganglionic sympathetic fibers that innervate viscera in abdominopelvic cavity course through?
Either synapse via thoracic, lumbar, and sacral splanchnic nerves to collateral ganglia or pass through all ganglia and syanpse with chromaffin cells of adrenal medulla
What type of cells are chromaffin cells on the suprarenal gland?
They are modified postganglionic sympathetic neurons, and receive innervation directly from preganglionic fibers
Where do postganglionic fibers destined for distribution within the neck, body wall, and limbs enter? Via what?
They enter the 31 sets of spinal nerves fro the sympathetic trunk to adjacent ventral and dorsal rami via gray communicating ramus
What 3 functions do postsympathetic fibers stimulate after passing through the spinal nerve?
1. Contract blood vessels
2. Contract arrector pili muscles
3. Cause sweat glands to secrete
Where do postganglionic sympathetic fibers to cause contraction of blood vessles, contraction of arrector pili muscles and sweat in the head synapse in (which ganglia)?
The superior cervical ganglion
What is another name for the outflow of the parasympathetic outflow based on where it occurs?
This is also known as craniosacral outflow, because the preganglionic sympathetic fibers originate in the brainstem or at the S2-S4 sacral fibers
Where are the cell bodies of parasympathetic postganglionic cells located?
In minute ganglia close to or within the organ it innervates
What is the exception to the "no parasympathetic innervation of the limbs or body wall" rule?
Erectile tissue receives parasympathetic innervation
What are the 4 parasympathetic ganglia that have specific names in the head region?
1. Ciliary ganglion - in orbital cavity
2. Pterygopalatine ganglion - pterygopalatine fossa
3. Otic ganglion - infratemporal fossa
4. Submandibular ganglion - floor of mouth
What four cranial nerves carry myelinated preganglionic fibers of the parasympathetic system?
1. Oculomotor nerve
2. Facial nerve
3. Glossopharyngeal nerve
4. Vagus nerve
Which cranial nerves carry parasympathetic fibers to which ganglia? (4 cranial nerves, 4 parasympathetic ganglia)
1. Oculomotor nerve -> ciliary ganglion
2. Facial nerve -> pterygopalatine and submandibular ganglion
3. Glossopharyngeal nerve -> otic ganglion
4. Vagus nerve: Provides most parasympathetic (75% of parasympathetic fibers) to thoracic viscera and foregut/midgut derivatives
What is the name of the parasympathetic fibers leaving the S2-S4 region (the sacral component of the craniosacral output)?
Pelvic splanchnic nerves