Pharmacology of the ANS

Question 1

Describe the neuronal structure of parasympathetic stimulation and give an example

Answer 1

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

Question 2

Describe the 3 neuronal structures of sympathetic stimulation and give an example

Answer 2

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

Question 3

Describe the neuronal structure of somatic motor stimulation and give an example

Answer 3

Only on neuron, synapses on muscle. Releases ACh to act on muscarinic receptors to cause muscle contraction

Question 4

How many subtypes of muscarninc receptors are there

Answer 4

5: M1->M5

Question 5

What are the possible Galpha groups in the GPCR of a muscarinic receptor

Answer 5

Gi
Go
Gq

Question 6

Describe an M2 receptor

Answer 6

Cardiac
Galpha i/o
works to to reduce cAMP

Question 7

Describe an M3 receptor

Answer 7

Smooth muscle, gland
Galpha q
Increases IP3 and DAG (contraction causing)

Question 8

How many subunits make up a nicotinic receptor

Answer 8

5

Question 9

Describe the subunits that make up a muscle nicotinic (N1) receptor

Answer 9

(alpha1)2Beta1GammaEpilson

Non selective cation channel

Question 10

Describe the subunits that make up a ganglionic nicotinic (N2) receptor

Answer 10

(alpha3)2(Beta4)3

Non selectibe cation channel

Question 11

What are the subtypes of alpha adrenergic receptors

Answer 11

alpha1, alpha2

Question 12

What effect do alpha1 adrenergic receptors have

Answer 12

activates Gq to stimulate IP3(Ca2+) and DAG second messenger pathways to increase intracellular Ca2+

Question 13

What effect do alpha 2 adrenergic receptors have

Answer 13

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

Question 14

What affect do Beta adrenergic receptors have

Answer 14

all activate Gs to increase cAMP

Question 15

Where are B1 receptors found

Answer 15

main cardiac subtype

Question 16

Where are B2 receptors found

Answer 16

main vascular and airways subtype

Question 17

Where are B3 receptors found

Answer 17

mainly in adipose tissue and bladder

Question 18

What are some NANC substances released by neurons

Answer 18

Neuropeptide Y + ATP

NO, VIP

Question 19

What is released to produce NANC vasoconstriction

Answer 19

NA and neuropeptide Y and ATP

Question 20

What is released to produce NANC vasodilation

Answer 20

ACh and NI and VIP

Question 21

How is high blood pressure regulated by the autonomic nervous system

Answer 21

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

Question 22

What are the parasympathetic effects on the heart

Answer 22

Inhibition of SAN (decreased hr, CO, BP)

reduced conduction velocity in AV node

Question 23

What are the parasympathetic effects on blood vessels

Answer 23

Few blood vessels are directly innervated (other than things like the penis)
PNS has little effect on TPR

Question 24

What does the injection of ACh into the blood stream cause within blood vessels and why

Answer 24

Causes vasodilation because there are cholinergic muscarinic receptors in blood vessels

Even though there is not normally any ACh in the blood

Question 25

What are the parasympathetic effects on bronchioles

Answer 25

Bronchioles constrict

Question 26

What are the parasympathetic effects on the GIT

Answer 26

Increased spontaneous contraction + intestinal sphincters relaxed

Question 27

What are the parasympathetic effects on the bladder

Answer 27

Detrusor muscle contracts, external sphincter relaxes causing micturition

Question 28

What nerve controls the parasympathetic innervation of the GIT and bronchioles

Answer 28

Vagus

Question 29

What nerves controls the parasympathetic innervation of the salivary glands

Answer 29

Glossopharyngeal nerve and facial nerve

Question 30

What nerve controls the parasympathetic innervation of the tear ducts

Answer 30

The facial nerve

Question 31

What is the parasympathetic effect on mucous secretion in the bronchioles

Answer 31

increases

Question 32

What are the parasympathetic effects on the eye and by which nerve are they mediated

Answer 32

accomodation of near sight by relaxation of ciliary muscle

pupil constriction by contraction of sphincter pupillae in iris

via oculomotor nerve

Question 33

What is the mechanism of action of botulinium toxin A

Answer 33

Binds to and degrades SNAP-25 prevents exocytosis of ACh and other NTs