ANS Flashcards
what are the 3 major divisions of the ANS?
1- sympathetic- fight or flight
thoracic cord
2- parasympathetic - rest and digest
cranial sacral
3- enteric- digestion and motility
gut
ANS is primarily an:
efferent effector system
ANS is controlled by the __ and __
hypothalamus and the solitary nucleus in BS
vagus nerve innervates everything except
lower GI and bladder
characteristics of the sympathetic NS?
preganglionic fibers originate from T1-L1 from Beta cells located within the lateral horn (intermediolateralis-lamina 7)
preganglionic fibers diverge onto postganglionic neurons
preganglionic fibers project in 1 of 4 ways
ratio of preganglionic fibers to postganglionic fibers = 1:10
GVA fibers comprises less than 20% of the total visceral fibers
–GVA are more noxious in function
preganglionic fibers release ACh while postganglionic fibers release NE
preganglionic fibers are short while postganglionic fibers are long
sympathetic chain ganglion lies outside the vertebral column (fiber splits from spinal nerve to enter ganglion through white ramus communicans)
what are the 4 ways preganglionic fibers can project?
1- directly to chain (paravertebral ganglion) and synapse on post ganglionic neurons (C unmyelinated fibers innervates periphery- smooth muscle, erector pillar, BVs)
2- enter chain and ascend to another level before synapsing onto postganglionic neurons (T1-5 ascend to supply the head; superior cervical, middle cervical & cervicothoracic ganglia)
3-enter chain and descend to another level before synapsing onto postganglionic neurons
4- go through paravertebral chain (no synapse) and join splanchnic nerves to synapse on prevertebral ganglia
what are the 4 ways preganglionic fibers can project?
myelinated preganglionic fibers leave the SC with the motor fibers of ventral roots T1-L2. the axons then separate from the spinal nerves to form the white rami communicantes which enter the chain ganglion of the sympathetic trunks. the trunks consist of paired, ganglionated chains of nerve fibers that extend along either side of the vertebral column from the base of the skull to the coccyx
1- some of the fibers of the white rami synapse with postganglionic neurons in the chain ganglion (paravertebral ganglion) nearest their point of entrance
2&3- other preganglionic fibers pass UP OR DOWN the chain to end in paravertebral ganglia at higher or lower levels than the point of entrance
4- preganglionic fibers pass through the paravertebral ganglion into the splanchnic nerves and terminate in the prevertebral ganglia of the abdomen and pelvis
sympathetic preganglionic fibers originate from:
T1-L1 from Beta cells located within the lateral horn (intermediolateralis -lamina VII)
what is the ratio of sympathetic preganglionic fibers to postganglionic fibers?
1:10
sympathetic GVA fibers comprise less than ____ of the total visceral fibers?
less than 20%
GVA are more noxious in function
sympathetic preganglionic fibers release ____, postganglionic fibers release ____
pre= ACh
post= NE
sympathetic preganglionic fibers are ____ while postganglionic fibers are _____
pre= short (in the viscera)
post= long
the parasympathetic NS is located in:
BS and sacral spinal cord
CNs 3 (eye),7 (glands), 9(throat), 10 (VAGUS) SNs S2-S4
parasympathetic postganglionic neurons are located in:
the structure that they innervate
PSNS preganglionic fibers are ___ while their postganglionic fibers are ____
pre=long
post=short
PSNS GVA fibers are:
more abundant and are more innocuous in function
more sensory involved- pressure and touch
primarily an efferent system
PSNS preganglionic fibers release ___ and postganglionic fibers release ____?
both release ACh as a transmitter
what is the ratio of PSNS preganglionic fibers vs postganglionic fibers?
1:3
most post
what is the PSNS also called?
cranial sacral NS
lower GI, bladder, sexual function all innervated at S2-4
control centers in the medulla
pre ganglionic fibers are:
B fibers
post ganglionic fibers are:
C fibers
what does the enteric NS innervate?
the GI tract, pancreas and gall bladder
can function autonomously
enteric NS plexuses are complex meshworks of ganglia and interconnecting nerve fibers located:
between the various layers of ms and endothelium
what are the 2 plexus from the enteric NS?
1- myenteric plexus
2-submucosal plexus
the myenteric plexus lies:
between the external longitudinal and circular smooth muscle layers
the submucosal plexus lies:
within the CT of the submucosa between the circular muscles and the mucosa
the enteric NS is regulated by:
the parasympathetic and sympathetic NS (an overriding system) (self regulating)
PNS makes it go faster
SNS makes it go slower
player before championship game collapses; no pulse; BP 60/45; breathing imperceptible; dilated pupils; pale face. unconscious for 15 seconds then returns to normal. reports feeling fine but weak.
what happened?
syncope
vasodepressor syncope or neurogenic shock
what is syncope?
fainting
brief loss of consciousness due to inadequate BF to the brain
what is vasodepressor syncope?
aka Neurogenic block
syncope caused by powerful emotions
strong emotions causes facilitation of SNS
vasodilation to muscles-increase blood to muscle, not enough to brain- causes a fall in BP
what is micturation?
urination
the micturation center is in the:
pons
part of reticular formation
PAG (periaqueductal grey) talks to pons
how the bladder works:
3 innervations to bladder
slide 12 and pg 37
3 bladder pathologies
1- reflexive: uninhibited reflex neurogenic bladder
2- automatic bladder
3- non reflexive bladder
what the major symptoms of uninhibited reflex neurogenic bladder?
voluntary control of filling and emptying bladder is completely lost
bladder fills and empties completely by reflex at pontine levels
therefore, normal emptying and filling, just no sensation (won’t be able to inhibit it if you have to pee bad)
what is the cause and location of uninhibited reflex neurogenic bladder?
UMN type
loss of all conscious perception of bladder filling or emptying
location: bilateral front lobe lesion (above the pons- lose the cerebrum- pons takes over)
keep diet the same and stay on a voiding schedule
what are the major symptoms of automatic bladder
bladder is incontinent- miturition control is lost
bladder empties incompletely- bc the spinal reflex pathways that trigger the pontine micturition center are gone
increased risk of bladder infection bc bladder retains urine
what is the cause and location of automatic bladder?
bilateral SC lesion about sacral levels
loss of pons control
what are the major symptoms of non-reflexive bladder?
bladder wall is flaccid and its capacity is greatly increased
bladder fills to capacity and overflows; continual dribbling is the result
prone to infection
pt doesn’t perceive bladder distention
keeps filling until it can’t stretch anymore- then urine dribbles out- VERY prone to infection
cathetorization needed
what is the cause and location of non-reflexive bladder?
LMN syndrome
sacral reflex arc are involved
location: bilateral lesion to sacral cord or pelvic nerves
