Autonomic Nervous System

Referred pain

-AKA reflective pain -afferent stretch fibers will follow sympathetic and parasympathetic innervation -afferent fibers traveling w/parasympathetic innervation---> regulating/sensing stretch receptors (environmental) -afferent fibers traveling w/sympathetic innervation---> associated w/ pain

Sympathetic nervous system cont.

-Sensory afferent neuron coming from ventral rami--> spinal nerve--> dorsal root ganglion--> dorsal root -motor efferent neurons have cell bodies in ventral horn--> ventral root--> spinal nerve--> ventral/dorsal rami -sympathetic chain is position anteriorally to the spinal nerve -IMLCC is located w/i lateral horn -sympathetic neurons project out ventral horn--> ventral root--> spinal nerve--> use gray/white ramus communicans -most lateral--> white ramus communicans (white bc more myelin) -white rami communicans will only have pre-ganglionic sympathetic innervation -to get off sympathetic chain, you can either exist via gray ramus communicans to get back on spinal nerve OR splanchnic nerves (sympathetic nerves) -superior to T5--> sympathetic nerves -inferior to T5--> splanchnic nerves -gray ramus communicans will only have post-ganglionic sympathetic innervation -sympathetic chain is a bilateral structure

sympathetic nervous system: foregut, liver, gall bladder & pancreas

-T5-T9 is the greater splanchnic nerve -can only call splanchnic nerve when all the individual splanchnic nerves come into one -greater splanchnic nerve pierce diaphragm and innervate foregut, liver, gall bladder & pancreas -splanchnic nerves are all *preganglionic sympathetic neurons* -once the splanchnic nerves get into collateral ganglion, they then synapse onto their postganglionic neuron and follow the blood supply to the organ -greater splanchnic nerve--> celiac ganglion--> synapse on post-synaptic sympathetic neurons--> follow the blood supply of celiac trunk

Nervous system divisions

-autonomic nervous system is a division from the motor neurons -autonomic nervous system is mainly efferent nerve innervated

activation of SNS and PNS

-hypothalamus, part of the diencephalon, sends signals down the spinal cord to vagal nuclei or IMLCC neurons in the spinal cord to activate parasympathetic or sympathetic nervous systems, respectively

sympathetic nervous system: hindgut

-inferior mesenteric ganglion run along inferior mesenteric artery which will supply blood to hindgut -preganglionic sympathetic innervation coming from L1/2 of IMLCC--> lumbar splanchnic nerves--> heading to aortic plexus--> synapse onto postganglionic sympathetic neurons of the inferior mesenteric ganglion--> following blood supply to hindgut -hindgut consist of left 1/3 of transverse colon to rectum summary: -preganglionic sympathetic innervation to the hindgut arise from IMLCC L1/2 and exist the sympathetic chain as lumbar splanchic nerves -lumbar splanchnic nerves mainly project to the inferior mesenteric ganglion to synapse onto postganglionic sympathetic neurons -postganglionic sympathetic neurons follow blood supply (inferior mesenteric artery) to viscera -sympathetic activation causes vasoconstriction and inhibitory to GI musculature

parasympathetic nervous system: hindgut

-instead of the parasympathetic innervation coming from the cranial region, it will come from sacral region S2/4 -in the S2/4 region of spinal cord, there is a small lateral horn where parasympathetic cell bodies will be located -the neurons will extent out the pelvic splanchnic nerves -only parasympathetic splanchnic nerves with parasympathetic innervation is *pelvic splanchnic nerves* -pelvic splanchnics coming from S2/4 going into inferior hypogastric plexus--> into rectal plexus summary: -preganglionic parasympathetic innervation to the hindgut arise from IMLCC of S2-S4 -preganglionic parasympathetic neurons will use the pelvic splanchnics to enter into the inferior hypogastric plexus, followed by the rectal plexus and follow the viscera to the postganglionic parasympathetic neurons -parasympathetic activation causes vasodilation, secretomotor to the GI mucosa and motor to the GI musculature

sympathetic nervous system: kidneys

-least splanchnic nerve innervation from T12 -least splanchnic nerve pierce diaphragm and go to two main ganglion: aorticorenal ganglion or renal ganglion where pregnaglionic neurons will synapse into postsynaptic sympathetic neuron that will then follow blood supply to kidney via renal plexus -renal plexus surround the renal artery which brings blood into kidney summary: -preganglionic sympathetic innervation to the kidney arise from IMLCC T12 to form the least splanchnic nerve in the thorax (will also receive contributions from the lesser splanchnic nerve) -the least splanchnic nerve projects mainly to the aorticorenal and renal ganglion to synapse onto postganglionic sympathetic neurons -postganglionic sympatehtic neurons follow blood supply (renal artery) to viscera -sympathetic activation causes vasoconstriction and decreased urine production -NOTE: the kidney mainly receives sympathetic innervation

sympathetic nervous system: midgut

-lesser splanchnic nerve will originate from T10-T11 IMLCC -NOTE: splanchnic nerves have NO function in thorax -they originate in the thorax and pierce diaphragm and enter the abdomen region -division between foregut and midgut is 1.5 of duodenum -duodenum has 4 parts: 1st, 2nd, 3rd, and 4th -midgut, starting at 1.5 of duodenum goes all the way to the left 1/3 of transverse colon -lesser splanchnic nerve--> superior mesenteric ganglion (another one of the collateral ganglion) -superior mesenteric ganglion will have postganglionic sympathetic neurons that will follow the blood vessels to viscera summary: -preganglionic sympathetic innervation to the midgut arise from IMLCC T10-T11 to form the lesser splanchnic nerve in the thorax -the lesser splancnic nerve projects mainly to the superior mesenteric ganglion to synapse onto postganglionic sympathetic neurons -postganglionic sympathetic neurons follow blood supply (superior mesenteric artery) to viscera -sympathetic activation causes vasoconstriction and inhibitory to GI musculature

parasympathetic nervous system

-long pre-ganglionic neuron -short post-ganglionic neuron -release ACh at both synpases -origin of pre-ganglionic neurons: craniosacral brainstem & spinal cord while the post-ganglionic neurons are located at the organ -vagus nerve running everywhere (thorax, abdomen, left 1/3 of transverse colon) -the only thing we talk about that doesn't receive vagus innervation is the hind gut -vagus nerve--> esophageal plexus--> anterior/posterior vagal trunk

sympathetic nervous system: thorax

-mainly neurons originate from T1-T4 -preganglionic neurons hop on to sympathetic chain and synapse in sympathetic ganglion and extend medially to go to cardiac plexus or pulmonary plexus

Sympathetic nervous system

-motor neuron cell bodies originate from the ventral horn of the spinal cord -ventral horn--> ventral root--> spinal nerve--> out ventral/dorsal rami -autonomic nervous system has two different neurons: pre-ganglionic neuron and post-ganglionic neuron -the length of the neurons and the neurotransmitters released differ for sympathetic and parasympathetic nervous systems -sympathetics have a short pre-ganglionic neuron and synapse on to post-ganglionic neuron using ACh -the post-ganglionic neuron release NE to activate adrenergic receptors -one exception to the two neuron rule is the adrenal medulla -adrenal medulla only going to have a preganglionic neuron extending to adrenal medulla and it is going to synapse on to chromaffin cells--> release NE and epinephrine into bloodstream--> these neurotransmitters can activate viscera directly -sympathetic nervous system pre-ganglionic neuron cell bodies originate in the thorcolumbar spinal cord -all sympathetics are coming from T1-L2 neurons -they originate from the intermediolateral cell column -lateral horn of the spinal cord is only present in the thoracolumbar region of the spinal cord -sympathetic neurons uses the *sympathetic chain* to ascend or descend

sympathetic nervous system: abdomen

-originate in IMLCC coming from T5-L2 -IMLCC--> ventral horn--> ventral root--> spinal nerve--> white rami communicans--> by-pass sympathetic chain--> splanchnic nerve--> synapse at collateral ganglion (preaortic ganglion)--> postganglionic sympathetic neurons going into GI tract -the splanchnic nerve originate in thoracic region but have no function there -the splanchnic nerves come from thoracic region and pierce diaphragm and innervate abdomen

pancreas

-pancreas has an exocrine and endocrine portion -endocrine--> insulin release into blood -exocrine--> more active during parasympathetic activation summary: -preganglionic sympathetic innervation to the foregut, liver, gall bladder and pancreas arise from IMLCC T5-9 to from the greater splanchnic nerve in the thorax -the greater splanchnic nerve projects mainly to the celiac ganglion to synapse onto postganglionic sympathetic neurons -postganglionic sympathetic neurons follow blood supply (celiac trunk) to viscera -sympathetic activation causes vasoconstriction of blood vessels, inhibitory to gastric musculature and secretions, decrease in bile production, increase in gluconeogenesis, decreased insulin and pancreatic secretions

parasympathetic nervous system: heart

-preganglionic parasympathetic innervation to the heart arises from vagal nuclei in brainstem -preganglionic parasympathetic neurons will use parasympathetic cardiac branches of vagus nerve to enter the cardiac plexus and heart to enter the cardiac plexus and heart tissue (synapse in cardiac plexus or heart tissue) -parasympathetic activation decreases rate and force of contraction by decreasing the activity of SA and AV nodes and vasoconstriction of coronary vessels

sympathetic nervous system: heart

-preganglionic sympathetic innervation to the heart arises from IMLCC T1-T4 -preganglionic sympathetic neurons will either ascend to higher levels (cervical) or stay at the same level of the sympathetic chain to synapse -preganglionic neurons will exist the sympathetic chain medially as cervical or thoracic sympathetic (cardiac) nerves to mix in the cardiac plexus before entering the heart tissue -sympathetic activation increases rate and force of contraction by increasing activity of SA and AV nodes and *vasodilation* of coronary arteries -NOTE: sympathetic innervation in peripheral blood vessels cause vasoconstriction

sympathetic nervous system: lungs & bronchi

-preganglionic sympathetic innervation to the lungs & bronchi arise from IMLCC T1-T4/5 -preganglionic sympathetic neurons will either ascend to higher levels (cervical) or stay at the same level of the sympathetic chain to synpase -postganglionic neurons will exist the sympathetic chain medially as cervical or thoracic sympathetic nerves and mix in the pulmonary plexus before following bronchi into lung tissue -sympathetic activation causes bronchodilation, vasoconstriction (shunting of blood to well ventilated areas) and inhibition of glandular secretion

Sympathetic nervous system cont.

-preganglionic sympathetic neurons will originate from T1-L2 and they can project in 4 different manners 1) enter through white rami communicans and synapse in sympathetic chain and follow spinal nerves to innervate *skin & blood vessels* 2) enter through white rami communicans and ascend or descend in sympathetic chain to another spinal level to then synapse at a ganglia and follow spinal nerves to innervate *skin & blood vessels* 3) enter through white rami communicans and synapse in sympathetic chain ganglia and exist medially to innervate *thorax* 4) enter through white rami communicans and exist sympathetic chain on splanchnic nerves to then synapse at collateral ganglia to innervate *abdomen*

sympathetic nervous system: skin & blood vessels

-skin and blood vessels have primarily sympathetic innervation -preganglionic sympathetic innervation to the skin and blood vessels arises from all sympathetic vertebral levels (T1-L2/3) -preganglionic sympathetic neurons will either synapse at the same level sympathetic ganglia or ascend/descend to other levels of sympathetic ganglia -postganglionic neurons will exist the sympathetic chain and use the spinal nerves to reach skin and blood vessels -sympathetic activation to the skin and blood vessels causes constriction of pilorrector muscles and vasoconstriction

Autonomic divisions

-sympathetic division AKA thoracolumbar division -parasympathetic division (around the sympathetic ) -parasympathetic division has a cranial-sacral outflow

sympathetic nervous system: adrenal gland

-the exception to the two series motor neuron -only has one motor neuron going directly to medulla -greater splanchnic nerve--> go directly to adrenal medulla and some will go to celiac ganglion and synapse and follow blood supply to cause vasoconstriction of vessels -those going directly to medulla are synapse on chromaffin cells (essentially act as postganglionic limb) -chromaffin will release epinephrine or NE into bloodstream and activate adrenergic receptors that way

Sympathetic nervous system cont.

-the sympathetic pre-ganglionic neurons originate from the IMLCC -the post-ganglionic neurons can be found in either the sympathetic chain or bypass the sympathetic chain and go to collateral ganglion (seen in abdomen)

Enteric nervous system (ENS)

-third division of autonomic nervous system -surrounds the GI tract -can function independently w/o input from CNS -can be influenced by the ANS -consists of two nerve plexuses surrounding the GI tract: 1-myenteric: controls motility 2-submucosal: blood flow and secretion sympathetic nerve influence on enteric nervous system: -IMLCC--> sympathetic chain--> by-pass sympathetic chain ganglion--> using splanchnic nerves--> synapse in collateral ganglion--> enteric nervous system/ walls of GI tract parasympathetic nerve influence on enteric nervous system: -vagus nerve--> synapse on the walls of GI tract

parasympathetic nervous system: midgut

-vagus nerve coming in as anterior/posterior vagal trunk running through the superior mesenteric ganglion, but not synapse there bc parasympathetic synapse on the wall of the organ summary: -preganglionic parasympathetic innervation to the midgut arise from vagal nuclei in brainstem -preganglionic parasympathetic neurons will use the anterior and posterior vagal trunks to enter into the abdomen and ramifies to synapse onto postganglionic parasympathetic neurons at the viscera -parasympathetic activation causes vasodilation, secretomotor to the GI mucosa and motor(peristalsis) to the GI musculature

parasympathetic nervous system: foregut, liver, gall bladder & pancreas

-vagus nerve is all preganglionic parasympathetic neurons extending from the brainstem going to the wall of the viscera the neuron will innervate. It will then synapse on to its extremely short postganglionic neuron at the wall of the viscera -vagus nerve DOES NOT follow the blood supply like the sympathetic nerve does -there are two vagal trunks: 1) anterior vagal trunk 2) posteior vagal trunk

parasympathetic nervous system: thorax

-vagus nerve--> parasympathetic branches--> anterior/posterior pulmonary plexus OR cardiac plexus -if coming from cervical region--> cervical cardiac nerves -if coming from thoracic region--> thoracic cardiac nerves -the nerves will enter cardiac plexus before innervating heart -once the neurons get into heart they then go into SA node and AV node

liver

sympathetic: -during sympathetic activation, liver has high amount of gluconeogenesis occurring -liver makes bile and stores in gallbladder -during sympathetic activation, liver doesnt make a lot of bile parasympathetic: -contract smooth muscle of gall bladder and open the gall bladder sphincter to exist gall bladder