ANS Part 1 Flashcards
What are the sympathetic and parasympathetic effects of stimulation on pupils?
sympathetic: dilate
parasympathetic: constrict
What are the sympathetic and parasympathetic effects of stimulation on salivation?
sympathetic: decreases saliva production
parasympathetic: increases saliva production
What are the sympathetic and parasympathetic effects of simulation on heart rate?
sympathetic: increase
parasympathetic: decrease
What are the sympathetic and parasympathetic effects of simulation on contractility (strength of heart contraction)?
sympathetic: increase
parasympathetic: decrease
What are the sympathetic and parasympathetic effects of simulation on the bronchi?
sympathetic: bronchiole dilation
parasympathetic: bronchiole constriction
What are the sympathetic and parasympathetic effects of simulation on the GI tract?
sympathetic: decreases activity
parasympathetic: increases activity
What are the sympathetic and parasympathetic effects of simulation on the adrenal medulla?
sympathetic: increases epinephrine (and some norepinephrine) release
parasympathetic: N/A
What are the sympathetic and parasympathetic effects of simulation on urination?
sympathetic: decreases urination (relaxes urinary bladder, constricts sphincter)
parasympathetic: increases urination (constricts urinary bladder, relaxes sphincter)
What are the sympathetic and parasympathetic effects of simulation on vasculature?
Sympathetic: general vascular tone. Increased sympathetic response leads to vasoconstriction.
Parasympathetic: N/A
Which branch of the ANS innervates sweat glands?
SNS
Which branch of ANS innervates blood vessels?
SNS only, but muscarinic receptors are present
What branch of ANS innervates ciliary muscle of the eye?
PNS only
What branch of the ANS innervates bronchial smooth muscle?
PNS only but B2 receptors are present
What is the somatic nervous system?
nerve impulses that are under voluntary control as well as reflexes
List a few endogenous neurotransmitters of the ANS
epinephrine
norepinephrine
dopamine
acetylcholine
What is a synapse?
The endpoint of a nerve where it releases its neurotransmitter for cell to cell communication.
The recipient cell can be another nerve cell or of the target organ.
Steps in NT synthesis & release
- NT is synthesized in presynaptic nerve terminal
- NT is stored in vesicles
- AP arrives at nerve terminal, depolarizes the cell –> vesicular fusion & release of NT
- NT reversibly binds to receptor on postsynaptic cell (neuron, adrenal medulla, effector organ)
- NT dissociates from receptor and is removed from synaptic cleft
Methods for NT removal from synaptic cleft
enzyme degradation, reabsorption, diffuses away
What neurotransmitter is released by the somatic nervous system? What receptor binds this neurotransmitter here?
Acetylcholine
Nicotinic (type 1) Receptor (Or Nm receptor)
What neurotransmitter is released into the synapse at all autonomic ganglion? What receptor binds this neurotransmitter here?
Acetylcholine
Nicotinic (type 2) Receptor (Or Nn receptor)
What neurotransmitter is released onto target organs from the parasympathetic nervous system? What receptor binds this neurotransmitter here?
Acetylcholine
Muscarinic (M) Receptor
What neurotransmitter is released onto target organs from the sympathetic nervous system? What receptors bind this neurotransmitter here?
Norepinephrine
Adrenergic Receptors (alpha1, alpha 2, Beta 1, Beta 2)
What neurotransmitter is released by the adrenal medulla? Where does this neurotransmitter go?
Primarily epinephrine - 80% (some norepinephrine - 20%)
It goes into the vascular circulation (hormones)
What type of receptor is located at the NMJ of the somatic NS?
Nm (N1)
What type of receptor is located at all autonomic ganglion?
Nn (N2)
What receptor is at all PNS effector organs?
M receptors
What type of receptors are at all SNS effector organs?
alpha & beta
How is acetylcholine metabolized?
Acetylcholinesterase (AChE)
How are epinephrine and norepinephrine metabolized?
COMT (catechol-o-methyltransferase) and
MAO (monoamine oxidase)
Where is Ach metabolized?
synaptic cleft
Where is Epi metabolized
liver, presynaptic terminal
Where is NE metabolized?
presynaptic terminal
How does the baroreceptor reflex respond to low blood pressure?
results in vasoconstriction & increased heart rate and/or contractility (increased cardiac output)
How does the baroreceptor reflex respond to high blood pressure?
results in vasodilation & decreased heart rate and/or contractility (decreased cardiac output)
How do drugs alter physiologic processes of the nervous system?
- alter axonal conduction (not common, local anesthetics)
- impact synaptic transmission (increase or decrease it)
Is alpha 1 located pre or post synaptic
POST
Location of a1 receptors
- most vascular smooth muscle
- arterioles in skin, viscera, mucous membranes, veins, sphincters, & bronchi
- iris (radial muscle)
- pilomotor smooth muscle
- prostate, trigone of bladder, uterus
- penis erectile tissue
List the main effects of alpha1 stimulation.
**vasoconstriction
pupillary dilation
bladder sphincter contraction
uterine contraction
**prostate contraction –> ejaculation
Is a2 located pre or post synaptically?
Pre and post
Where are a2 receptors located?
- platelets (postsynaptic)
- adrenergic & cholinergic nerve terminals (pre)
- vascular smooth muscle (pre & post)
- GI tract (pre)
- CNS (pre)
List the main effects of alpha2 stimulation
- platelet aggregation
- inhibits NT release –> decrease action of neurotransmission
- vasoconstriction & vasodilation
- GI tract relaxation
- CNS: decreased SNS outflow, sedation & analgesia
Is b1 located pre or post synaptically?
post
B1 receptor location
heart & kidneys
List the main effects of beta1 stimulation
**heart: increased contractility, rate, AV node conduction velocity
renin release from kidneys
Is b2 pre or post synaptic
post
B2 location
- smooth muscle of bronchioles, uterus, vascular (skeletal muscle, heart, lungs), GI/GU
- skeletal muscle
- liver
List the main effects of beta2 stimulation
**bronchodilation
**uterine relaxation
**vasodilation in skeletal muscle, heart, & lungs
**decreased GI/GU motility
**increased K+ uptake (–> hypokalemia)
tremor
increased speed of skeletal musc contraction
**glycogenolysis (–> hyperglycemia)
Dopamine location
postsynaptic
vascular smooth muscle (renal, mesentery, heart, CNS)
List the main effects of dopamine1 stimulation
vasodilation of coronaries & renal vasculature
Agonist
stimulates the receptor to do what it normally does
Selectivity decreases with
increasing doses –> off target effects
Direct agonists
directly interact with receptor
Indirect agonists
increases NT concentration
Antagonist
blocks the normal activated receptor activity
Affinity
strength of drug binding to the receptor
Endogenous catecholamines
epi, NE, dopamine
List the two synthetic catecholamines
dobutamine
isoproterenol
Catecholamines vs non
- 1/2 life of catecholamines is short due to rapid breakdown by MAO/COMT, cannot be given PO
- non have longer 1/2 life (no COMT, slow MAO); ok for PO
- catecholamines cannot cross BBB, non can
MAO
- monoamine oxidase
- lives in presynaptic nerve terminals
- breaks down catecholamines after reuptake
- drug - drug interactions w/ MAOI
COMT
- catechol-O-methyltransferase
- mostly liver but also presynaptic nerve terminals, some cytoplasm
- adds methyl group to catechols (can eliminate)
What can happen when giving a patient a MAO inhibitor?
Hypertension and tachycardia (this can lead to stroke, myocardial infarction, etc.)
Which receptors does epinephrine agonize?
a1, a2, B1, B2
Which receptors does norepinephrine agonize?
a1, a2, B1
Which receptor does phenylephrine agonize?
a1 > a2
Which receptor does midodrine agonize?
a1 >a2
Which receptor does clonidine agonize?
a2 > a1
Which receptor does dexmedetomidine agonize?
a2 > a1
Which receptor does dobutamine agonize?
B1 > B2
Which receptors does isoproterenol agonize?
B1 & B2
Which receptor does terbutaline & albuterol agonize?
B2 > B1
Which receptor does dopamine agonize at low doses? At medium doses? At high doses?
dopaminergic
medium dose = B1
high dose = a1
Do catecholamines or noncatecholamines have a longer duration of action?
noncatecholamines
Major adverse effect of epinephrine?
tachydysrhythmias
(tachycardia with rapid AV conduction that can lead to abnormal beats)
this can lead to myocardial infarction
Since norepinephrine doesn’t agonize ____, it produces the strongest _____.
B2; vasoconstriction
what is an indirect agonist
drug that acts via a mechanism that is NOT directly agonizing the receptor
examples:
- blocking reuptake of neurotransmitter
- blocking metabolism of a neurotransmitter
- increasing release of neurotransmitter from presynaptic nerve terminal
when giving a beta antagonist for hypertension, what are side effects of using a nonselective antagonist?
bronchoconstriction (esp risk with asthma)
hypoglycemia (esp risk with diabetes)
hyperkalemia
does receptor selectivity increase or decrease when the dose of medication increases
decrease
what are the three types of receptors in the parasympathetic nervous system?
nicotinic N (N1 or Nn)
nicotinic M (N2 or Nm)
muscarinic (5 major subtypes)
what neurotransmitter is released in the parasympathetic and somatic nervous systems
acetylcholine
Nn agonism occurs where?
all SNS & PSNS ganglia
adrenal medulla
Nm agonism occurs where?
neuromuscular junction (the synapse between a nerve and the muscle cell)
Nm agonism results in _______.
skeletal muscle contraction
agonism of muscarinic receptors result in:
- vasodilation
- **decreased heart rate
- miosis
- **bronchoconstriction
- **increased secretions
- **GI/GU motility increase (urination/defecation)
- sweating
- erection
what is an acetylcholinesterase inhibitor
medication that blocks the actions of acetylcholinesterase, which results in increased acetylcholine concentration
Sympathetic and Parasympathetic effect on reproductive system
- SNS: orgasm in genitals of men and women
- PNS: stimulates erection of genitals
Structure of ANS
preganglionic neuron –> postganglionic neuron –> effector organ
SNS pre and postganglionic neurons
pre = short, post = long; quicker transmission
PNS pre and postganglionic neurons
pre = long, post = short; slower transmission
SNS primary functions
maintain blood flow to vital organs (brain), body temperature regulation, fight or flight reaction
SNS - maintenance of blood flow
increase HR & contractility, vasoconstriction in specific vessels
SNS - body temperature regulation
sweating, piloerection, controls blood flow to skin
SNS - fight or flight reaction
pupillary dilation, decreased GI motility / less digestion, detrusor muscle relaxation (less urge to urinate), bronchodilation
PNS regulatory functions
- decreased HR
- increased gastric secretions
- emptying of bladder (detrusor & trigone muscle action)
- emptying of the bowel
- eye focusing on near vision
- pupillary constriction
- bronchoconstriction
Baseline tone
both systems exhibit at rest to maintain homeostasis; most organs are innervated by both PNS & SNS to maintain tight homeostatic control