L6 - Drugs Affecting the Autonomic Nervous System (Part I)

Question 1

What is the role of the autonomic nervous system (ANS)?

Answer 1

• The ANS conveys outputs from the central nervous system (CNS) to the rest of the body, except for skeletal muscle contraction.

Question 2

Is the autonomic nervous system voluntary or involuntary?

Answer 2

• The autonomic nervous system is largely involved in involuntary control.

Question 3

What are the functions regulated by the autonomic nervous system?

Answer 3

• It regulates contraction and relaxation of smooth muscle, exocrine and endocrine secretions, heartbeat, and energy metabolism.

Question 4

What are the key components of a neuron?

Answer 4

• A neuron consists of a cell body, an axon, and a nerve terminal.

Question 5

What is the role of the nerve terminal in a neuron?

Answer 5

• The nerve terminal releases neurotransmitters that can act on other neurons, muscles, or glands.

Question 6

What is a ganglion?

Answer 6

• A ganglion is a collection of neuron cell bodies outside the CNS with innervating nerve terminals.

Question 7

How many divisions does the autonomic nervous system have, and what are they?

Answer 7

• The autonomic nervous system has three divisions: sympathetic, parasympathetic, and enteric.

Question 8

Which divisions of the autonomic nervous system are primarily focused on in the lecture?

Answer 8

• The focus is on the sympathetic and parasympathetic divisions.

Question 9

What is the general anatomical pattern of the autonomic nervous system?

Answer 9

• Both sympathetic and parasympathetic divisions follow a two-neuron pattern with preganglionic and postganglionic neurons.

Question 10

Where are the parasympathetic ganglia located?

Answer 10

• Parasympathetic ganglia usually lie close to or within the target organ.

Question 11

Where are the sympathetic ganglia located?

Answer 11

• Sympathetic ganglia are found as paravertebral chains and midline ganglia.

Question 12

What are the main activities of the sympathetic and parasympathetic systems?

Answer 12

• Sympathetic activity increases during stress, while parasympathetic activity predominates during satiation and repose (rest and digest).

Question 13

How do sympathetic and parasympathetic systems affect organs?

Answer 13

• They can produce either opposing or similar effects on organs.

Question 14

How is information relayed from the CNS to target organs?

Answer 14

• An impulse from the CNS travels down a preganglionic neuron, releasing a chemical that excites the postganglionic neuron, which in turn releases chemicals that bind to receptors on the target organ.

Question 15

How do drugs affect autonomic neurotransmission?

Answer 15

• Drugs can bind to receptors at various points in the pathway, affecting neurotransmission in the autonomic nervous system.

Question 16

What are the two main chemicals in the autonomic nervous system?

Answer 16

• The two main chemicals are acetylcholine and noradrenaline.

Question 17

What neurotransmitter is released by neurons leaving the CNS?

Answer 17

• All neurons leaving the CNS release acetylcholine, which acts on nicotinic acetylcholine receptors.

Question 18

What neurotransmitter is released by parasympathetic postganglionic neurons?

Answer 18

• Parasympathetic postganglionic neurons release acetylcholine, which acts on muscarinic acetylcholine receptors.

Question 19

What neurotransmitter is released by sympathetic postganglionic neurons?

Answer 19

• Sympathetic postganglionic neurons release noradrenaline, which may act on α- or β-adrenoceptors, with an exception for the sweat glands.

Question 20

What are nicotinic acetylcholine receptors?

Answer 20

• Nicotinic acetylcholine receptors are ligand-gated ion channels that allow increased Na+ permeability, sending action potentials and exciting cells.

Question 21

Where are muscle-type nicotinic receptors located?

Answer 21

• Muscle-type nicotinic receptors are found at the skeletal neuromuscular junction.

Question 22

What role do ganglionic nicotinic receptors play?

Answer 22

• Ganglionic nicotinic receptors are responsible for transmission in both the sympathetic and parasympathetic systems.

Question 23

What are CNS-type nicotinic receptors, and where are they found?

Answer 23

• CNS-type nicotinic receptors are widespread in the brain and are excitatory.

Question 24

What is the effect of drugs that act as agonists of ganglionic nicotinic receptors?

Answer 24

• These drugs activate nicotinic ACh receptors in ganglia, stimulating transmission in the autonomic nervous system and affecting various tissues and organs.

Question 25

Why are ganglionic nicotinic receptor agonists of limited therapeutic use?

Answer 25

* Because they affect almost all autonomic functions, leading to complex and widespread effects.

Question 26

What are some examples of ganglionic nicotinic receptor agonists?

Answer 26

* Examples include nicotine and dimethylphenylpiperazinium (DMPP).

Question 27

What are the effects of ganglionic nicotinic receptor agonists on the body?

Answer 27

* Effects include tachycardia, increased blood pressure, variable gastrointestinal motility, and increased secretions from glands such as bronchial and salivary glands.

Question 28

What are examples of ganglionic nicotinic receptor antagonists (blockers)?

Answer 28

* Examples include hexamethonium, trimetaphan, and tubocurarine.

Question 29

What are the effects of blocking ganglionic nicotinic receptors?

Answer 29

* Effects include hypotension, loss of cardiovascular reflexes, inhibition of secretions, gastrointestinal paralysis, and impaired urination.

Question 30

What is the current clinical use of ganglionic nicotinic receptor antagonists?

Answer 30

* These drugs are clinically obsolete, except for the occasional use of trimetaphan in anesthesia to produce controlled hypotension.

Question 31

What are muscarinic acetylcholine receptors (mAChRs)?

Answer 31

* Muscarinic acetylcholine receptors are G-protein-coupled receptors (GPCRs) found on tissues such as the heart, smooth muscle, and glands.

Question 32

What are the main types of muscarinic acetylcholine receptors?

Answer 32

* The two main types are M2 and M3 receptors.

Question 33

What is the role of M2 muscarinic acetylcholine receptors?

Answer 33

* M2 receptors are found on the heart and have mainly inhibitory effects, reducing cardiac rate and force of contraction.

Question 34

What is the role of M3 muscarinic acetylcholine receptors?

Answer 34

* M3 receptors are found on glands and smooth muscle, causing secretion and contraction.

Question 35

How do M2 muscarinic acetylcholine receptors inhibit the heart?

Answer 35

* They inhibit the heart by activating K+ channels, causing hyperpolarization, and inhibiting adenylate cyclase, reducing cAMP levels and Ca2+ conductance.

Question 36

How do M3 muscarinic receptors stimulate smooth muscle and glands?

Answer 36

* M3 receptors increase intracellular Ca2+ levels by activating IP3, leading to smooth muscle contraction and glandular secretion.

Question 37

What are examples of muscarinic acetylcholine receptor agonists?

Answer 37

* Examples include acetylcholine, muscarine, pilocarpine (used for glaucoma), and bethanechol (stimulates bladder and gastrointestinal smooth muscle).

Question 38

What are examples of muscarinic acetylcholine receptor antagonists?

Answer 38

* Examples include atropine (blocks all mAChRs and has various effects) and ipratropium (M3 antagonist used for asthma).

Question 39

How does botulinum toxin affect acetylcholine release?

Answer 39

* Botulinum toxin cleaves proteins involved in vesicle release, thereby preventing acetylcholine release.

Question 40

What is the role of acetylcholinesterase (AChE)?

Answer 40

* Acetylcholinesterase (AChE) breaks down acetylcholine into acetate and choline, regulating free acetylcholine levels.

Question 41

What drug inhibits acetylcholinesterase, and what is its use?

Answer 41

* Ecothiopate inhibits acetylcholinesterase and is used as eye drops to treat glaucoma.