What are the preganglionic and postganglionic neurotransmitters for the somatic nervous system, the PNS, and SNS?
PNS: preganglionic & postganglionic-Ach
SNS: preganglionic-Ach, postganglionic-NE
In regards to the SNS, where do preganglionic B fibers originate?
In the intermediolateral cell column segments T1-L2 or L3
In regards to the SNS, where do preganglionic B fibers exit the spinal cord?
With the ventral ramus.
In regards to the SNS, once the preganglionic B fibers exit the spinal cord with the ventral ramus they synapse. Where do they synapse?
Synapse in the lateral chain ganglia along the ventrolateral surface of the vertebral bodies or pass thru to synapse in other (collateral) sympathetic ganglia.
What type of neuron leave the ganglia and travel to segmental nerves & target organs?
Postgagnlionic neurons (unmyelinated C fibers).
Describe the lateral chain ganglia?
Paravertebral ganglia T1-L2 on the anterolateral surface of the vertebral bodies.
What are the collateral ganglia?
Cardiac, celiac, superior & inferior mesenteric ganglia.
What do the collateral ganglia accommodate?
Preganglionic fibers which do not synapse in lateral chain, but continue in visceral ramus->splanchnic nerves which end in collateral ganglia.
What are the superior cervical ganglion?
What are the middle cervical ganglion?
What are the inferior cervical ganglion?
C7 & C8
What are the target organs of the superior cervical ganglions (C1-C4)?
Iris & ciliary body
Lacrimal & salivary glands
What are the target organs of the middle cervical ganglions (C5-C6) & the stellate ganglions?
All preganglionic fibers arise below the stellate, blockade at this level affects all sympathetics above this level.
Describe the lumbo-sacral lateral chain
Receives all presynaptic input enters from L1 & L2.
These ganglia are not fused but the coccygeal ganglia meet at the midline
What forms the stellate ganglion?
Inferior cervical ganglion fuses w/ T1.
What are the target organs for the celiac ganglion?
Stomach, small bowel, adrenal medulla
Where does the cardiac plexus receive its sympathetic input from?
What are the target organs of the superior mesenteric ganglion?
Large & small bowel
What are the target organs of the inferior mesenteric ganglion?
Lower colon & rectum
What are the target organs of the hypogastric ganglion?
What ganglions are supplied by the greater, lesser, & least splanchnic nerves?
Greater & lesser: celiac plexus
Least: inferior mesenteric & hypogastric ganglia
Blocking what ganglion will knock out all the sympathetics, why, and what can it result in?
Stellate ganglion. All preganglionic fibers arise below the stellate ganglion.
Could result in Horner's syndrome
Blocking what plexus is indicated in treatment of intraabdominal malignancies & chronic pancreatitis; diagnostic (local or therapeutic (neurolytic block)?
Blocking what ganglion is indicated in painful conditions of the lower extremities and pelvic viscera and vascular insufficiency in the legs?
Lumbar sympathetic ganglion.
Blocking what plexus and ganglion is indicated in tx of painful conditions of the pelvis and perineum?
Superior hypogastric plexus & ganglion impar
Describe the cervical lateral chain.
Located in the neck. All presynaptic input enters from T1 w/ minor contributions from T2 & T3. Cervical lateral chain ganglia are fused.
Where do all sympathetics to the head & neck come from?
T1 or below
Where is the cervical sympathetic chain located?
Lies on the anterolateral surface of the vertebral bodies.
Where does the cervical sympathetic chain receive its input from?
T1 or below
Blocking what ganglion is indicated in treatment & diagnosis of pain syndromes, vascular insufficiency, hyperhidrosis, and dysrhythmias?
What are the S/S of Horner's syndrome?
Ptosis (drooping of eyelid), flushing, miosis (pupillary constriction), anhidrosis (lack of sweating).
Describe the cardiac plexus
Superficial & deep divisions.
Both organized around the aortic arch.
Where do the celiac ganglion (collateral ganglion) receive its input?
From the greater & lesser splanchnic nerves.
What does sympathetically mediated pain involve (CRPS)?
An initiating event-crush, stretch, axotomy, ischemia, etc... to a peripheral nerve.
What does CRPS stand for?
Complex regional pain syndrome.
What occurs with sympathetically mediated pain?
There is a sensitization of peripheral (C-fibers) & central (dorsal horn laminae 1& 2).
What does the sensitization of peripheral (C-fibers) & central (dorsal horn laminae 1& 2) involve?
↑ spontaneous neuronal activity d/t ectopic pacemakers (probably dysfunctional Na channels)
↑ response to stimuli
↓ stimulus threshold (less stimulation required to cause nerves to fire).
What does C fiber sensitization lead to?
↑ adrenergic receptors
↑ sensitivity to stimuli (↑ action potential per stimulus)
↑ "cross talk"
What is "cross talk"?
Phenomenon where neurons carrying normal sensory info cross over & are interpreted as high intensity pain & accounts for allodynia
Describe the dorsal horn changes that occur w/ sympathetically mediated pain.
A-beta fibers form abnormal connections in shallow laminae (1 & 2)->normal sensory input interpreted as high intensity noxious stimuli.
↑ gene expression for receptors for pain related neurotransmitters (substance P).
↓ opioid binding sites.
Describe the wind-up theory.
Involves repetitive noxious stimuli (c-fibers)->prolonged discharge of dorsal horn cells-> progressive ↑ in APs per stimulus->long term potentiation (LTP).
What occurs with LTP?
↑ in receptive field of nociceptive neurons d/t formation of more dendrite connections in the dorsal horn.
Dropout of inhibitory neurons.
What are NMDA receptors important for?
In triggering wide dynamic range (WDR) neurons that are responsible for generalization of specific nociceptive info.
What are the NMDA agonists and what releases them?
Aspartate, glutamate, etc-released by c-fiber stimulation.
What are the NMDA antagonists, what are they useful for?
Ketamine, dextromethorphan, methadone, PCP
Useful in chronic pain syndrome
In regards to the lumbo-sacral lateral chain, where do most sympathetic fibers to the lower ext pass thru, and what would blockade at this level cause?
Pass thru L2/L3. Causes near complete sympathectomy of the lower ext.
In regards to the cardiac plexus, where does sympathetic input arise from?
In regards to the cardiac plexus, where does parasympathetic input arise from?
Vagus & recurrent laryngeal nerves.
Describe "cross talk".
Abnormal connections by demyelinated (loss of myelin d/t some sort of neurologic phenomenon) neurons called ephapses.