ANS Flashcards
What are the functions of the ANS?
Maintain homeostasis
Respond to changing physiologic conditions
Increase or decrease effector activity
What are the 2 division of the ANS?
Sympathetic NS
Parasympathetic
Where on the spinal cord does the SNS originate?
Thoraco-lumbar
T1-L2
Where on the spinal cord does the PSNS originate from?
Cranio-sacral
Cranial nerves and S2-S4
What cranial nerves have PSNS fibers?
III
VII
IX
X
Where are the sympathetic ganglia?
Near the spinal cord
Where are the parasympathetic ganglia?
Near the target organ
Describe preganglionic efferent fibers:
+/- myelin
Fiber type
Short or long
Preganglionic efferent SNS fibers are
Myelinated
Type B
Short
Describe preganglionic efferent PSNS fibers:
+/- myelin
Fiber type
Short or long
Preganglionic efferent PSNS fibers are:
Myelinated
Type B
Long
Describe postganglionic efferent SNS fibers:
+/- myelin
Fiber type
Short or long
Postganglionic efferent SNS fibers are:
Unmyelinated
Type C
Long
Describe postganglionic efferent PSNS fibers:
+/- myelin
Fiber type
Short or long
Postganglionic efferent PSNS fibers are:
Unmyelinated
Type C
Short
What is the sympathetic chain, and what is another name for it?
The sympathetic chain is a bundle of nerves that runs from the base of the skull to the coccyx just lateral to the vertebral bodies
Paravertebral ganglia
What supplies the sympathetic chain?
Rami communicates
What are the 2 branches of the rami communicates?
White ramus (myelinated) Grey ramus (unmyelinated)
Where is the preganglioic cell body in the SNS?
The lateral horn of the spinal cord
What spinal root do the SNS fibers pass through?
The ventral root and into the corresponding spinal nerve
What is the first ramus SNS fibers pass through after leading the spinal canal, and where to the continue to?
The White ramus and into the sympathetic chain
What are the 3 paths a preganglionic SNS fiber can take after reaching the sympathetic chain?
- Synapse at the same level
- Travel up or down the chain to synapse
- Exit to synapse at a ganglion outside the sympathetic chain
What is the place where SNS preganglioic fibers travel to synapse if they just pass through the sympathetic chain?
Prevertebral ganglion
AKA
Contralateral ganglia
If the SNS synapse occurs in the sympathetic chain what are the 2 things that can happen next with the postganglionic fiber?
- Travel to the target organ
- Enter the grey ramus leading back to the spinal nerve and follow the skeletal nerve to blood vessels of skeletal muscle, piloerector muscle, or sweat glands
What is the most significant prevertebral ganglia to anesthesia?
Stellate ganglion
What is the stellate ganglion? How does blockage manifest?
Provides sympathetic inner action to the IPSP lateral upper extremity and a portion of the head and neck.
Blockade manifests as Horner’s syndrome: ptosis, anhydrous is, miosis, and enophthalmos
What activity is the majority of PSNS activity?
Vagus
75% (3/4)
Responses in which ANS division are energy conserving and which are energy expending?
Responses in the SNS are generally energy expending
Responses in the PSNS are generally energy conserving
Do all organs have SNS and PSNS innervation?
No, some have both and some only have one
Give an example of something that is only innervated by one ANS division
Blood vessels are only innervated by the SNS.
SNS causes vasoconstriction
Vasodilation is caused by just less SNS activity
What is the neurotransmitter utilized by preganglionic fibers in the SNS? PSNS?
All preganglionic fibers are cholinergic and use acetylcholine
What neurotransmitter is utilized by postganglionic fibers in the SNS? PSNS
SNS: are adrenergic and use norepinephrine (expect for sweat glands)
PSNS: are cholinergic and use acetylcholine
What neurotransmitter do cholinergic synapses respond to?
Acetylcholine
Where are cholinergic synapses located (3)?
ANS ganglia
PNS end organ
Neuromuscular junction
What are the receptors types at cholinergic synapses?
Nicotinic
Muscarinic
What are the subtypes of Nicotinic cholinergic receptors? Where are each located?
Nn: SNS ganglionic synapse and PSNS ganglionic synapse
Nm: Neuromuscular junction
Where are muscarinic receptors located?
At the PSNS end organs
Also found at SNS end organ sweat glands
What muscarinic receptor subtype is specifically important to Taylor and why?
M2: stimulation by PSNS at M2 causes bradycardia
What do adrenergic synapses respond to?
Endogenous catecholamines:
Norepinephrine
Epinephrine
Dopamine
What are the 2 types of adrenergic receptors?
Alpha
Beta
What adrenergic receptor(s) does norepinephrine stimulate?
Alpha
What adrenergic receptor(s) does epinephrine stimulate?
Both alpha and beta
Where are most alpha 1 receptors located? What stimulates them? What is the response?
Most are located in vascular smooth muscle
Stimulated by norepinephrine
Causes vasoconstriction
(Phenylephrine, levophed)
What happens if alpha 1 antagonists are given?
Vasodilation
Prazosin
Where are beta 1 receptors mostly located? What stimulates them? What is the response?
Most beta 1 receptors are located in the heart.
Stimulated by epinephrine and norepinephrine.
Response is increased HR, contractility, automaticity and conduction
(Dobutamine, dopamine, isoproterenol-mixed)
What happens if beta 1 antagonists are given?
Cardiac depression
Metoprolol etc., propranolol-mixed
Where are beta 2 receptors located? What stimulates them? What is the response?
Beta 2 receptors are located in some blood vessels (skeletal and coronaries), bronchioles, uterus, kidney, liver, pancreas.
Stimulated by epinephrine and norepinephrine.
Responses: vasodilation, bronchodilation, smooth muscle relaxation, improved glucose metabolism
Where are dopamine receptors located? What stimulates them? What is the response?
In the kidneys and splanchnic vasculature.
Stimulated by dopamine.
Response: relaxation, increased blood flow to kidneys and abdominal viscera
If the dopamine receptor is not considered adrenergic, why is dopamine considered an adrenergic agonist?
Because at higher doses dopamine does agonize other adrenergic receptors
Where are alpha 2 receptors located? What stimulates them? What is the response?
Found presynaptically and in the CNS.
Stimulated by norepinephrine.
Engaged alpha 2 receptor acts to inhibit neurotransmitter release by that neuron resulting in decreased SNS activity
Most blood vessels are pure have what receptor?
Alpha 1 - stimulation causes vasoconstriction and less stimulation causes dilation
Skeletal muscle vessels have what receptor?
Beta 2 - stimulation causes vasodilation
Besides beta 2, what other receptor do skeletal muscle vessels also have?
Sympathetic cholinergic (muscarinic) - stimulation causes vasodilation
What is dysautonomia?
ANS dysfunction
What s/sx are seen with ANS dysfunction?
Orthostatic hypotension - baroreceptor would be impaired Urinary retention Bowel dysfunction Impotence Parkinsonism - Parkinson-like symptoms
What can cause ANS dysfunction?
Degeneration - Shy Drager
Neuropathy - like from DM
Inherited
Idiopathic
What are the anesthesia implication of ANS dysfunction?
Hypotension - to with volume, direct acting pressors
