Autonomic Nervous System

Question 1

Drugs that target the ANS mimic or block the actions of what class of molecules?

Answer 1

neurotransmitters

Question 2

Which part of the nervous system do most drugs influence (regardless of whether that system is targeted or not)?

Answer 2

ANS

Question 3

How many steps if the process of signaling the effector organs through the ANS?

Answer 3

2 steps (pre and post ganglionic)

Question 4

What are the two major divisions of the ANS and where are they located? Where do they originate from?

Answer 4

Sympathetic (thoracolumbar) and parasympathetic (craniosacral). Originate in nuclei in the CNS

Question 5

Where do the sympathetic preganglionic fibers terminate and where do the post ganglionic fibers run to?

Answer 5

terminate in ganglia of the paravertebral chains and run to tissues

Question 6

Where do the parasympathetic preganglionic fibers terminate and where do the post ganglionic fibers run to?

Answer 6

terminate in walls of innervated organs and run to more specific location within the organ

Question 7

What neurotransmitter is used by the somatic nervous system and to which receptor does it bind?

Answer 7

Acetylcholine binds to Nm-type nicotinic receptor (Nm=nicotinic muscle)

Question 8

Which neurotransmitter is released by both the sympathetic and parasympathetic preganglionic neurotransmitters and to what receptor does it bind?

Answer 8

acetylcholine binds to Nn-type nicotinic receptor on postganglionic neurons (nicotinic neuronal)

Question 9

What neurotransmitter is used by postganglionic parasympathetic neuron and to which receptor does it bind?

Answer 9

Acetylcholine binds to a muscarinic receptor (G-protein linked)

Question 10

What neurotransmitter is used by postganglionic sympathetic neuron and to which receptor does it bind?

Answer 10

Norepinephrine binds to adrenergic receptor of type a or b (G protein linked)

Question 11

Name 3 exceptions where sympathetic post ganglionic fibers do not release norepinephrine.

Answer 11

1. Sweat glands-ACH
2. Renal Vascular Smooth Muscle-Dopamine
3. Chromaffin cells are specialized post-ganglionic neurons that release epi and NE from the adrenal medulla

Question 12

Which division of the ANS tends to have a more widespread output and which tends to be more discrete?

Answer 12

Sympathetic-more widespread (pre:post is 1:20)

Parasympathetic-more discrete (Pre:post is 1:1)

Question 13

Where is the enteric nervous system located?

Answer 13

in the walls of the GI system

Question 14

Where does the enteric nervous system get input from?

Answer 14

preganglionic parasympathetic fibers, postganglionic sympathetic fibers, and sensory input from the wall of the gut

Question 15

What does the enteric nervous system control?

Answer 15

smooth muscle of the gut, and secretory cells (motility and secretion)

Question 16

Explain the synthesis of Ach.

Answer 16

From acetyl coA and choline by choline acetyltransferase, then packaged into vesicles for storage

Question 17

Explain the degradation of Ach.

Answer 17

acetylcholinesterase-mediated cleavage of ACH into acetate and choline which are then recycled

Question 18

Why are drugs that block the synthesis, storage and release of ACH not particularly useful?

Answer 18

effects are not selective

Question 19

What is the mechanism of action of Botulinum toxin A

Answer 19

blocks local Ach release to inhibit muscle contraction

Question 20

Explain the synthesis of NE.

Answer 20

1. tyrosine hydroxylated to DOPA
2. DOPA decarboxylated to dopamine
3. within vesicles dopamine is hydroxylated to NE

Question 21

Explain the termination of NE signaling.

Answer 21

within the cleft diffusion and reuptake; outside the cleft NE is metabolized and excreted

Question 22

What are drugs that block NE synthesis, storage and release used to treat?

Answer 22

hypertension

Question 23

To which G protein are M2 and M4 receptors coupled and what is it’s effect intracellularly?

Answer 23

they are coupled to Gi and inhibit adenylate cyclase (decreases cAMP) and activate K+ channels causing hyperpolarization

Question 24

To which G protein are M1, M3 and M5 receptors coupled and what is it’s effect intracellularly?

Answer 24

they are coupled to Gq which activates phospholipase C causing increase in DAG and IP3 leading to increased Ca2+ levels

Question 25

Where are alpha 1 and 2 adrenergic receptors located?

Answer 25

vascular smooth muscle, presynaptic nerve terminals, and platelets in the brain

Question 26

Where are beta adrenergic receptors located?

Answer 26

on most types of smooth muscle, cardiac muscle, some presynaptic nerve terminals and the brain

Question 27

What is the main effect of alpha 1 adrenergic receptor activation?

Answer 27

increase in PLC leading to increase in IP3 and DAG leading to smooth muscle contraction

Question 28

What is the main effect of alpha 2 adrenergic receptor activation?

Answer 28

inhibition of Adenylate Cyclase leading to decrease in cAMP, and activation of K+ channel (hyperpolarization); inhibition of NT release

Question 29

What is the main effect of beta 1 adrenergic receptor activation?

Answer 29

Increase in adenylate cyclase causing increase in cAMP leading to increase in force and rate of contraction of heart

Question 30

What is the main effect of beta 2 adrenergic receptor activation?

Answer 30

Increase in adenylate cyclase causing Increase in cAMP leading to smooth muscle relaxation

Question 31

What is the main effect of beta 3 adrenergic receptor activation?

Answer 31

Increase in adenylate cyclase causing Increase in cAMP leading to lipolysis

Question 32

What are presynaptic receptors that respond to the transmitter substances released called?

Answer 32

autoreceptors

Question 33

Are autoreceptors usually inhibitory or excitatory?

Answer 33

inhibitory

Question 34

Name 5 major targets for drugs to modulate the ANS.

Answer 34

transmitter synthesis, storage, release and termination and NT receptors.

Question 35

How to nicotinic neuronal and nicotinic muscular receptors differ from each other?

Answer 35

subunit composition, each is made up of 5 subunits but the subunits differ

Question 36

Action and receptor for sympathetic nervous system on SA node?

Answer 36

accelerates; Beta 1 and 2 receptors

Question 37

Action and receptor for parasympathetic nervous system on SA node?

Answer 37

decelerates; M2 receptor

Question 38

Action and receptor for sympathetic nervous system on Bronchiolar Smooth muscle?

Answer 38

relaxes; Beta 2 receptor

Question 39

Action and receptor for parasympathetic nervous system on bronchiolar smooth muscle?

Answer 39

contracts; M3 receptor

Question 40

Action and receptor for sympathetic nervous system on Bladder wall?

Answer 40

relaxes; Beta 2

Question 41

Action and receptor for parasympathetic nervous system on Bladder wall?

Answer 41

contracts; M3