Pharmacology of the ANS Flashcards
Describe the neuronal structure of parasympathetic stimulation and give an example
Preganglionic neuron synapses with postganglionic neuron at effector tissue releasing ACh to act on a nicotinic receptor. The postganglionic neuron releases ACh to work on a muscarinic receptor for example on a salivary gland
Describe the 3 neuronal structures of sympathetic stimulation and give an example
1: Preganglionic neuron synapses with postganglionic neuron at ganglion not in the effector tissue releasing ACh to act on a nicotinic receptor. The postganglionic neuron releases NA to act on alpha or beta adrenergic receptors on the effector (e.g blood vessels)
2: Preganglionic neuron synapses with postganglionic neuron at ganglion not in the effector tissue releasing ACh to act on a nicotinic receptor. The postganglionic neuron releases ACh to act on muscarinic receptors on the effector (e.g blood vessels)
3: There is only one neuron, synapsing directly on the surface of the adrenal medulla which in turn secretes NA and adrenaline to act on alpha and beta receptors on the effector
Describe the neuronal structure of somatic motor stimulation and give an example
Only on neuron, synapses on muscle. Releases ACh to act on muscarinic receptors to cause muscle contraction
How many subtypes of muscarninc receptors are there
5: M1->M5
What are the possible Galpha groups in the GPCR of a muscarinic receptor
Gi
Go
Gq
Describe an M2 receptor
Cardiac
Galpha i/o
works to to reduce cAMP
Describe an M3 receptor
Smooth muscle, gland
Galpha q
Increases IP3 and DAG (contraction causing)
How many subunits make up a nicotinic receptor
5
Describe the subunits that make up a muscle nicotinic (N1) receptor
(alpha1)2Beta1GammaEpilson
Non selective cation channel
Describe the subunits that make up a ganglionic nicotinic (N2) receptor
(alpha3)2(Beta4)3
Non selectibe cation channel
What are the subtypes of alpha adrenergic receptors
alpha1, alpha2
What effect do alpha1 adrenergic receptors have
activates Gq to stimulate IP3(Ca2+) and DAG second messenger pathways to increase intracellular Ca2+
What effect do alpha 2 adrenergic receptors have
activates Gi to inhibit adenylyl cyclase (decreases cAMP production). Often presynaptic, it sits on the presynaptic membrane and some NA will diffuse back and bind to it instead of at the post-synaptic membrane reducing NA release
What affect do Beta adrenergic receptors have
all activate Gs to increase cAMP
Where are B1 receptors found
main cardiac subtype
Where are B2 receptors found
main vascular and airways subtype
Where are B3 receptors found
mainly in adipose tissue and bladder
What are some NANC substances released by neurons
Neuropeptide Y + ATP
NO, VIP
What is released to produce NANC vasoconstriction
NA and neuropeptide Y and ATP
What is released to produce NANC vasodilation
ACh and NI and VIP
How is high blood pressure regulated by the autonomic nervous system
Parasympathetic:
Increased BP distends arterial walls- stretch receptors stimulated.
Passed to NTS (nucleus tractus solitarius)
Increased parasympathetic stimulation
Decreased HR + CO
Sympathetic:
Decreased sympathetic drive to the heart
Decreased heart rate and force of contraction => lowered CO
decreased arterial and venous constriction therefore lovered TPR
BP = CO x TPR so lowered
What are the parasympathetic effects on the heart
Inhibition of SAN (decreased hr, CO, BP)
reduced conduction velocity in AV node
What are the parasympathetic effects on blood vessels
Few blood vessels are directly innervated (other than things like the penis)
PNS has little effect on TPR
What does the injection of ACh into the blood stream cause within blood vessels and why
Causes vasodilation because there are cholinergic muscarinic receptors in blood vessels
Even though there is not normally any ACh in the blood
What are the parasympathetic effects on bronchioles
Bronchioles constrict
What are the parasympathetic effects on the GIT
Increased spontaneous contraction + intestinal sphincters relaxed
What are the parasympathetic effects on the bladder
Detrusor muscle contracts, external sphincter relaxes causing micturition
What nerve controls the parasympathetic innervation of the GIT and bronchioles
Vagus
What nerves controls the parasympathetic innervation of the salivary glands
Glossopharyngeal nerve and facial nerve
What nerve controls the parasympathetic innervation of the tear ducts
The facial nerve
What is the parasympathetic effect on mucous secretion in the bronchioles
increases
What are the parasympathetic effects on the eye and by which nerve are they mediated
accomodation of near sight by relaxation of ciliary muscle
pupil constriction by contraction of sphincter pupillae in iris
via oculomotor nerve
What is the mechanism of action of botulinium toxin A
Binds to and degrades SNAP-25 prevents exocytosis of ACh and other NTs
