Flashcards in Intro to ANS Deck (65):
portion of the central and peripheral NS that is responsible for unconscious control of the visceral function
CONSTANT control of visceral function
i.e. decreased heart rate, shunting of blood toward the gut away from the skeletal muscle
cranial part of the parasympathetic division
sacral part of parasympathetic division
lateral horn (intermediolateral cell column)
responsible for control of visceral reaction response to IMMEDIATE STRESS (fight or flight)
thoracolumbar portion of sympathetic division
IMLCC lateral horn of spinal cord levels T1-L2
collection of neurons within the CNS?
visceral efferent fibers of the ANS are accompanied by visceral afferent fibers
visceral afferents PARALLEL the course of the sympathetic division, generally carrying visceral pain
visceral afferents (mostly vagal) can be FOUND WITHIN branches of cranial nerves VII, IX and X . These are responsible for the modailty of distention (feeling full)
where are the presynaptic neuron cells bodies of the sympathetic nervous system found?
in the CNS--> intermediolateral cell column
the intermediolateral cell column is found from T1-L2
where do the cell bodies of postsynaptic neuron of the sympathetic NS reside?
sympathetic trunk/chain ganliga
extend the length of the spinal column
attached to spinal nerve trunks (rami) which conduct specific nerve fibers (white and gray ramus communicans)
white ramus communicans
conduct MYELIN preganglionic sympathetic fibers from a spinal nerve to a paravertebral ganglion
Gray ramus communicans
conduct unmyelinated post-ganglionic sympathetic fibers from a paravertebral ganglion to a spinal nerve
pre-vertebral ganglia (collateral)
located ANTERIOR to the vertebral column (anterior to the aorta)
superior and inferior mesenteric ganglia
preganglionic fiber of ANS
efferent fiber from the preganglionic neuron (cell bodies located within CNS)
postganglionic fiber of ANS
fiber from the second neuron (cell bodies located within peripheral ganglion)
for the parasympathetic nervous system where does the postganglionic fiber reside typically?
within the walls of organs that it innervates
EXCEPT in the head specifically where parasympathetic ganglia exist near organs (salivary glands and eyes)
what is the vagus nerve and what does it innervate
innervates thoracic and abdominal viscera (most of the GI tract)
sympathetic division of ANS innervates
all visceral organs AND visceral organs of the periphery
pass out INTO SPINAL NERVES
Head, salivary glands
T1-3,4 (head AND neck)
stomach, liver, gallbladder, pancreas
T5/6-L1 or L2
the sympathetic chain is attached to....
every single spinal nerve
why is the gray ramus ONLY postganglionic
there are no other ganglia peripherally other than the sympathetic chain
so everything that leaves by the gray ramus must be postganglionic
3 different pathways of preganglionic sympathetic fibers after passing through white rami communicants to sympathetic chain ganglia...
1- Synapase on a postganglionic neuron at the same LEVEL OF ENTRY (so T1-L2)
2- ascend or descend a few segments
-ascend --> head, neck and upper limb
-descend --> lower limb
3- pass through the sympathetic chain and ganglion without synapsing to pass via splanchnic nerve to a prevertebral ganglion
sympathetic chain ...
parallells ALL SPINAL NERVES
sweat glands and erector pilae muscles
a sympathetic PREGANGLIONIC fiber that does not synapse in a paravertebral ganglion, but rather synapses distally in a PREVERTEBRAL ganglion closer to the organs which they innervate
takes information to the gut
there are no preganglionic sympathetic fibers above T1 or below L2
so the only way you get preganglionic information into area that is opposite spinal nerves where there is no intermediolateral cell column is via sympathetic chain
what is found larger quantities?postsynaptic sympathetic fibers or presynaptic
each presympathetic fiber synapses with 30 or more postsympathetic fibers
function of postsynaptic sympathetic fibers
stimulate contraction of blood vessels and arrector muscles associated with hairs
and cause sweating
sympathetic innervation to the heart and lungs
cardiopulmonary splanchnic nerve
the postganglionic cell body for these is and EXCEPTION!!! b/c it actually synapses in the sympathetic chain and not out in prevertebral ganglia
presynaptic parasympathetic nerve fibers exit via this nerve and synapse in plexuses on the surface of organs or arteries (unnamed ganglionics)
these arise at spinal cord levels S2-S4
part of the sacral outflow of parasympathetic system
Exception to the rule that parasympathetic fibers are characteristically not found in spinal nerves!!!
sit in front of aorta
this is where splanchnic nerves come to synapse
greater splanchnic nerve
goes through diaphragm--> synapse on celiac ganglion
liver, stomach, spleen, pancreas, duodenum
lesser splanchnic nerve
T10-11 goes through diaphragm
kidney and gonad
least splanchnic nerve
lumbar splanchnic nerve
what are autonomic plexuses?
sympathetic and parasympathetic fibers travel together as plexuses on the surface of arterial blood vessels
only the postganglionic parasympathetic fiber does not exist within these plexuses as it can only be found within the walls of the organs they are destined to innervate
although parasympathetic fibers may travel on the surface of arteries....
THEY DO NOT INNERVATE THEM
in which division of the ANS is the ratio of postganglionic to preganglionic fibers much greater?
the sympathetic division and this is because of the more "global" effect of the sympathetic NS versus the more "local" effect of the parasympathetic NS
what is the neurotransmitter for the synapse of the preganglionic fiber with the postganglionic neuron in para and sympathetic NS?
what is the neurotransmitter for the synapse of postganglionic fibers on the effector organs for parasympathetic vs sympathetic
parasympathetic --> Ach
sympathetic --> norepinephrine (NE)
two types of visceral pain
dull or nauseous
what causes dull nauseous pain
distention of a hollow organ
parasympathetic nervous system
not very well localized due to their cranio-sacral innervation
what causes acute or sharp pain?
registered by visceral afferent fibers which return to the spinal cord along routes which parallel the sympathetic system
why is acute pain well localized?
since preganglionic sympathetic fibers arise from specific segments of the spinal cord and travel within all spinal nerves, pain fibers which parallel them enter the spinal cord at the exact same spinal levels as the origin of sympathetic EFFERENT fibers
viscera and dermatomes?
viscera are segmentally innervated by branches of spinal nerves that correlate to the dermatomes
AND Afferent fibers for pain travel with the sympathetic visceral motor system. THEREFORE dermatomes which are implicated in referred pain syndromes are limited to levels T1-L2
what happens when disease or infection occur internally over a protracted period of time?
stimulate ascending tract neurons to the point that their stimulation is perceived
the brain incorrectly thinks this pain is coming from the surface of the body at the same spinal level as the incoming visceral afferents
THIS IS THE BASIS OF REFERRED PAIN
what can visceral afferent fibers entering the spinal cord synapse on? and what will be the outcome of this synapse
basis for viscerosomatic reflex
can synapse on interneurons that synapse on cells of the lateral and ventral horns
LOTS OF NEUROTRANSMITTER bathing these nerves so they are excitable and fire automatically
these interneurons can then stimulate two things:
1. preganglionic sympathetic nerve fibers causing vascular smooth muscle contraction
2. ventral motor horn cell stimulation causing contraction of paraspinal musculature
visceral afferent stimulation resulting in somatic responses
can include change in the character of the connective tissue due to reduced vascular flow (increased sympathetic tone)
or can include tightness due to increased somatic muscular tone and referred pain
important note about visceral afferents and splanchnics...
visceral afferents that parallel sympathetic splanchnic nerves return to the identical spinal cord levels of visceral efferent innervation
a segment of spinal cord that has facilitated somatic changes due to visceral input
areas of SD those that display the effects of vescerosoatic reflexes can lead to the identification and localization of visceral disease