SNS Review Flashcards
8% of the spinal nerves are composed of
Sympathetic C fibers
The pre-ganglionic neurotransmitter of the SNS is
Acetylcholine
The post-ganglionic neurotransmitter of the SNS is
-With one exception
Norepinephrine
The one exception to NE being the post-ganglionic neurotransmitter in the SNS is seen in
Sweat glands (ACh)
The rate limiting step in the synthesis of dopamine occurs in the cytoplasm and is the conversion of
L-tyrosine to L-DOPA
The enzyme that catalyzes the conversion of L-Tyrosine to L-DOPA is
Tyrosine Hydroxylase (TH)
Blocks vesicular monoamine transport of dopamine to synaptic vesicles
Reserpine
Conversion of norepinephrine to epinephrine occurs ONLY in the
Adrenal medulla
What enzyme catalyze the conversion of NE to Epi?
PNMT
High concentrations of NE in the Vessicle are maintained by
VMAT and NE binding to ATP
The action potential then leads to Ca2+ influx and
NE release
NE reuptake occurs at the presynaptic terminal by
NE Transporter
Inhibit NE reuptake into presynaptic terminal
Cocaine and TCA
NE is metabolized to an inactive metabolite by
MAO (mitochondria) and COMT (liver)
What are the three main classes of adrenergic receptors?
Alpha-1, alpha-2, and Beta
Increase IP3, Dracula glycerol, and calcium channel activity
Alpha-1 agonists
Decrease cAMP and calcium channel activity and increase K+ conductance
Alpha-2 agonist
Function to increase cAMP
Beta 1,2, and 3 agonists
Alpha-1 adrenergic receptors are located on the
Post-Synaptic Membrane
Linked to Gq, and increase intracellular calcium
Alpha-1 adrenergic receptors
Alpha-1 activation cause which three main things?
Vasoconstriction (increased BP), Urinary retention, and Mydriasis
Increase smooth muscle contraction
Alpha-1 agonists
Has minimal effects on the heart
Alpha-1 stimulation
Causes increased systemic vascular resistance and increased BP
Peripheral vasoconstriction
Causes bladder outlet obstruction and increased intraocular pressure
Alpha-1 agonists
Alpha-2 adrenergic receptors are located on the
PRE-synaptic membrane
Inhibit neurotransmitter release
-Inhibits both NE and ACh
Alpha-2 receptors
Decrease aqueous humor production
Alpha-2 agonists
All three Beta receptors increase
cAMP
Beta-1 receptors are located on
Post-synaptic membrane
Cardiac Beta-1 receptors cause increased
Contractility, HR, and Conduction
Renal Beta-1 receptors cause increased
Renin
SNA stimulation increases
Inotropy
Activation of beta-1 receptors increases cAMP, which in turn activates
PKA
Sympathetic nerve stimulation opens
Na+ and L-type Ca2+ channels
Activation of Beta-2 receptors in smooth muscle results in increased
Bronchodilation, vasodilation, and Uterine relaxation
In the liver, causes glycogenolysis and gluconeogenesis, thus increasing glucose
Beta-2 receptor activation
In the muscle, beta-2 activity causes a decrease in
Potassium
Located on adipocytes where they increase lipolysis
Beta-3 receptors
Beta receptor signaling can be terminated by
Phosphorylation
