Anatomy of Autonomics: An Introduction Flashcards
What is the PNS divided into functionally?
sensory and motor divisions
What are sensory and motor inputs of the PNS subdivided into?
somatic (body) and visceral (guts)
general and special
What is the afferent division?
sensory
What is the efferent division?
motor
What are general somatic sensory functions?
touch, pain, pressure, vibration, temperature, and proprioception in skin, body wall, and limbs
What are special somatic sensory functions?
hearing, equilibrium, and vision
What does the somatic motor nervous system innervate?
all skeletal muscles
What does the autonomic nervous system innervate?
smooth muscle, cardiac muscle, and glands
What is the ANS divided into?
sympathetic division and parasympathetic division
What does the general visceral motor division of the PNS regulate?
heart rate, blood pressure, digestion, and urination
Is there pain when visceral organs are cut?
no
What causes pain in visceral organs?
chemical irritation or inflammation
What is visceral pain perceived as?
somatic origin, referred pain
Where are the presynaptic neurons located?
in the CNS
Where are the postsynaptic neurons located?
in the periphery
What is the function of the ANS?
regulate involuntary (unconscious) body functions and maintain internal physiological homeostasis
Which ANS division is catabolic?
sympathetic
Where is the sympathetic nervous system?
all vascularized portions of body
What is the sympathetic ANS responsible for? Exception?
vasoconstriction of vessels.
Exception: coronary arteries
Which division of ANS is anabolic?
parasympathetic conserves energy
Where is the parasympathetic ANS located?
head, neck, body cavities, genitalia
Where is the parasympathetic ANS not found?
body wall or limbs
Is glandular secretion sympthetic or parasympathetic?
parasympathetic except sweat glands
effect of sympathetic stimulation on eyes
dilates pupil
effect of sympathetic stimulation on skin
arrector muscles: causes hair to stand on end
peripheral blood vessels: vasoconstricts (blanching skin, lips, and fingertips blue)
sweat glands: promotes sweating
effect of sympathetic stimulation on other glands
lacrimal glands: slightly decreases secretion
salivary glands: salvation decreases, becomes thicker, more viscous
effect of sympathetic stimulation on heart
increases rate and strength of contraction; inhibits parasympathetic effects on coronary vessels allowing dilation
effect of sympathetic stimulation on lungs
inhibits effects of parasympathetic system, resulting in bronchodilation and reduced secretion, allowing maximum air exchange
effect of sympathetic stimulation on digestive tract
inhibits peristalsis, and constricts blood vessels to digestive tract so that blood is available to skeletal muscle; contracts internal anal sphincter to aid fecal continence
effect of sympathetic stimulation on liver and gallbladder
promotes breakdown of glycogen to glucose (for increased energy)
effect of sympathetic stimulation on urinary tract
vasoconstriction of renal vessels slows urine formation; internal sphincter of bladder contracted to maintain urinary continence
effect of sympathetic stimulation on genital system
causes ejaculation and vasoconstriction resulting in remission of erection
effect of sympathetic stimulation on supraenal medulla
release of adrenaline into blood
effect of parasympathetic stimulation on eyes
pupil: constricts
ciliary body: contracts allowing lens to thicken for near vision
effect of parasympathetic stimulation on skin
arrector muscles: none
peripheral blood vessels: none
sweat glands: none
effect of parasympathetic stimulation on other glands
lacrimal glands: promotes secretion
salivary glands: promotes abundant, watery secretion
effect of parasympathetic stimulation on heart
decreases the rate and strength of contraction (conserving energy); constricts coronary vessels in relation to reduced demand
effect of parasympathetic stimulation on lungs
constricts bronchi (conserving energy) and promote bronchial secretion
effect of parasympathetic stimulation on digestive tract
stimulates peristalsis and secretion of digestive juices
contracts rectum, inhibit internal anal sphincter to cause defecation
effect of parasympathetic stimulation on liver and gallbladder
promotes building/conservation of glycogen; increases secretion of bile
effect of parasympathetic stimulation on urinary tract
inhibits contraction of internal sphincter of bladder, contracts detrusor muscle of the bladder wall causing urination
effect of parasympathetic stimulation on genital system
produces engorgement (erection) of erectile tissues of the external genitals
effect of parasympathetic stimulation on suprarenal medulla
no effect (doesn’t innervate)
length of postsynaptic (postganglionic) fibers of sympathetic
long postsynaptic fibers
length of postsynaptic (postganglionic) fibers of parasympathetic
short postsynaptic fibers
branching of sympathetic fibers
highly branched to influence many organs at once
branching of parasympathetic fibers
few branches for localized effect
Neurotransmitter released by sympathetic postsynaptic axons
most release norepinephrine (adrenergic) except sweat glands (cholinergic)
Neurotransmitter released by parasympathetic postsynaptic axons
acetylcholine (cholinergic)
Neurotransmitter released by presynaptic neurons in sympathetic and parasympathetic
both release cholinergic neurotransmitters
Where are presynaptic (preganglionic) neurons of the sympathetic division found?
intermediolatearl (lateral) gray horn of spinal cord (between anterior and posterior horns)
Where do presynaptic fibers of the sympathetic division exit?
spinal nerves ventral roots T1 to L2/3
length of presynaptic fibers of sympathetic division
short
What are sympathetic trunk ganglia also called?
paravertebral or chain ganglia
Where are sympathetic trunk ganglia found?
both sides of the vertebral column
What does the sympathetic division supply?
entire body with sympathetic innervation
Where does the chain of ganglia extend?
uppermost cervical level to coccyx level
Where are the additional sympathetic ganglia located?
What are they called?
outside the chain of ganglia around the vascular branches of the anterior abdominal aorta
collateral, prevertebral, or preaortic ganglia
Where are the presynaptic sympathetic neuron cell bodies located?
lateral horn
What do communicating nerves in the sympathetic trunk do? What are they called?
transmit the presynaptic axons and posynaptic axons from the spinal nerves
white rami communicans
Where do postsynaptic sympathetic axons reenter the spinal nerves?
gray rami communicans
Where are gray rami communicans found?
C1 to Co1
Where is post synaptic sympathetic innervation distributed?
body walls and extremities - arrector pilli muscles, sweat glands, blood vessels
Are sympathetic presynaptic neurons myelinated?
yes
What is the path of sympathetic neurons?
spinal cord (intermediolatearl horn) send myelinated axons through adjacent ventral root into spinal nerve, white rami communicans carry axons from spinal nerve to associated sympathetic trunk ganglia where they synapse, gray rami communicans carry postsynaptic fibers back to spinal nerve through ventral and dorsal rami to travel to peripheral structures
Can sympathetic pathway synapse at levels other than the same vertebrae?
yes, a level up or down especially in cervical and sacral levels
What is a splanchnic nerve?
term used to describe nerves transmitting axons of either sympathetic or parasympathetic neurons that supply the viscera
Where are thoracic splanchnic nerves found?
abdomen and pelvis
Where do splanchnic nerves lie?
anterior to the vertebral column
Where do splanchnic nerves synapse?
prevertebral (collateral) ganglia on the abdominal aorta, celiac, and superior and inferior mesenteric ganglia
What is the function of prevertebral ganglia?
inhibit activity of muscles and glands in visceral organs
What is the adrenal medulla?
major organ of the sympathetic nervous system
Where do sympathetic preganglionic fibers of the adrenal medulla synapse?
medullary chromaffin cells
What do chromaffin cells release?
great quantities of norepinephrine and epinephrine into the blood
What is the exception to the 2-neuron pathway for the ANS?
adrenal medulla
Which presynaptic sympathetic neuron axons pass through the sympathetic trunk without synapsing?
T8-L1
After passing though the sympathetic trunk without synapsing, what do T8-L1 presynaptic sympathetic neuron axons go?
enter abdomen as splanchnic nerves to adrenal medulla to synapse on chromaffin cells (nonneurons)
What is cranial outflow?
presynaptic parasympthetic neurons located in the brainstem exiting via cranial nerves that innervate organs of the head, neck, thorax, and abdomen
Where does sacral outflow emerge from? supply and innervate?
S2-S4
organs of the pelvis and lower abdomen
Where are presynaptic cell bodies of the sacral outflow of parasympathetic nervous system? Where do axons run?
visceral motor region of spinal gray matter (intermediolateral column)
axons run in ventral roots out via ventral rami
Where are pelvic splanchnic nerves formed?
sacral outflow, distributed via inferior hypogastric plexus to the viscera where they synapse with postsynaptic neurons within the organs
What cranial nerves do the presynaptic parasympathetic neurons leave the brainstem?
III, VII, IX, X
What cranial nerves are the post synaptic parasympathetic cranial portion neurons associated with?
III, VII, and IX
What ganglia are the postsynaptic neurons of the parasympathetic cranial portion located?
ciliary, pterygopalatine, submandibular, and otic ganglia
What do the postsynaptic fibers from ciliary, pterygopalatine, submandibular, and otic ganglia innervate?
smooth muscle in the eye, lacrimal and salivary glands, and nasal and oral mucosa
What cranial nerve do presynaptic parasympathetic fibers travel down into thorax and abdomen?
CN X vagus nerve
Where are presynaptic parasympathetic sacral portion located?
S2-S4 of sacral spinal cord
What is the path of the presynaptic fibers of parasympathetic sacral part?
pass through anterior rami and then branch off as pelvic splanchnic nerves that make their way to the pelvic viscera via hypogastric plexus and synapse with postsynaptic neurons located within the pelvic and lower GI viscera
What does the enteric nervous system consist of?
neurons in the wall of the GI tract from the esophagus to the anus. Also include postsynaptic neurons of cranial nerve X and pelvic splanchnic nerves.
What is the function of the enteric nervous system?
autonomous functions such as GI reflexes (sensory and motor)
Where are enteric neurons located?
smooth muscle layer of the stomach and intestines and in submucosa
