Parasympathetic Nervous System and Cholinergic Receptors

Question 1

What are the primary ANS neurotransmitters?

Answer 1

Acetylcholine and Norepinephrine

Question 2

Where are Acetylcholine and Norepinephrine synthesized and stored?

Answer 2

They are both synthesized in nerve terminals and stored in synaptic or varicosity vesicles until released by nerve impulse.

Question 3

Where is acetylcholine found in the peripheral nervous system?

Answer 3

ACh is the primary neurotransmitter at 3 different sites:

1) All preganglionic synapses in both the parasympathetic and sympathetic ganglions
2) Most parasympathetic postganglionic nerve endings/neuroeffector junctions
3) All somatic motor end-plates on skeletal muscle

Question 4

All neurons/axons/fibers that release ACh are called:

Answer 4

Cholinergic

Question 5

Where is the NT norepinephrine found in the ANS?

Answer 5

1) Most sympathetic postganglionic neuroeffector junctions

2) Adrenal Medulla cells (chromatin) release both norepinephrine and epinephrine

Question 6

Neurons/axons/fibers that release NE are called:

Answer 6

Adrenergic

Question 7

Cholinergic neurons release:

Answer 7

ACh

Question 8

What are drugs that mimic the action of ACh called?

Answer 8

Cholinergic, cholinomimetic, parasympathomimetic

Question 9

What are drugs that antagonize the action of ACh called?

Answer 9

Anticholinergic, cholinergic blockers, parasympatholytic

Question 10

What are receptors on which ACh or cholinergic drugs act called?

Answer 10

Cholinergic receptors or cholinoreceptors

Question 11

Adrenergic neurons release:

Answer 11

Norepinephrine

Question 12

Drugs that mimic the action of NE are called?

Answer 12

adrenergic, adrenomimetic, sympathomimetic

Question 13

Drugs that antagonize the cation of NE are called?

Answer 13

antiandrenergic, adrenergic blockers, sympatholytic

Question 14

What are receptors on which NE or adrenergic drugs act called?

Answer 14

adrenergic receptors, adrenoceptors

Question 15

What is the primary NT of the parasympathetic nervous system?

Answer 15

ACh

Question 16

What are the steps of ACh synthesis and storage?

Answer 16

• Synthesized in the axonal cytoplasm from acetylCoA and choline via ChAT
• AcetylCoA comes from mitochondria
• Choline comes from extracellular fluid via choline transporter (CHT)
• ACh is transported into neuronal vesicles via vesicle-associated transporter (VAT)

Question 17

What can block choline transporter (CHT)?

Answer 17

hemicholiniums

Question 18

What can block vesicle-associated transporter (VAT)?

Answer 18

vesamicol

Question 19

How is ACh released?

Answer 19

1) Vesicle-associated membrane proteins (VAMPs) - align vesicle with release sites on inner nerve terminal membrane
2) Synaptosomal nerve-associated proteins (SNAPS) - located on the inner nerve terminal and interact with VAMPs
3) Action potential reaches nerve terminal that triggers Ca++ influx via calcium channels
4) Ca++ interacts with VAMPs synaptotagmin (Ca++ sensor), triggering fusion of vesicle membrane with terminal membrane
5) ACh is then released via exocytosis into the synaptic cleft

Question 20

What can block ACh release into the synaptic cleft?

Answer 20

botulinum toxin

Question 21

What happens the ACh in the synaptic cleft?

Answer 21

It can bind to ACh receptors to result in effector response

All ACh molecules are rapidly metabolized by acetylcholinesterase (AChE)

AChE rapidly hydrolyzes ACh into acetate and choline, which terminates the action of ACh

Question 22

What is critical to the fine control of neurotransmission?

Answer 22

Rapid removal of the NT

Question 23

What are the ACh receptor subtypes?

Answer 23

Muscarinic receptors and Nicotinic receptors

Question 24

Where are Muscarinic receptors located?

Answer 24

Smooth muscle, cardiac muscle, exocrine glands

Question 25

What type of receptors are muscarinic receptors and what kind of responses do they exhibit?

Answer 25

GPCR – they have slower responses and may be either inhibitory or excitatory

Question 26

Where are Nicotinic receptors located?

Answer 26

Three places:

1) Postganglionic neurons in both sympathetic and parasympathetic
2) Adrenal medulla
3) Skeletal muscle

Question 27

What type of receptors are nicotinic receptors and what kind of responses do they exhibit?

Answer 27

Ligand-gated ion channels – they always cause a rapid increase in permeability to Na+ and K+, depolarization and excitation

Question 28

What is the function of Gs in GPCRs?

Answer 28

Increase in adenylyl cyclase activity, then increase in Ca++ currents

Question 29

What is the function of Gi in GPCRs?

Answer 29

Decrease in adenylyl cyclase activity, then increase in K+ currents

Question 30

What is the function of Go in GPCRs?

Answer 30

Decrease in Ca++ currents

Question 31

What is the function of Gq in GPCRs?

Answer 31

Increase in phospholipase C activity