11-Drugs affecting the ANS

Question 1

What are the receptors of the somatic nervous system? Which neurotransmitter is associated with these receptors?

Answer 1

Nicotinic Cholinergic Receptors. Acetylcholine.

Question 2

Which drugs are used to block the somatic nervous? What is the effect of these drugs?

Answer 2

Neuromuscular Blocking Agents. Induce paralysis of skeletal muscle.

Question 3

When are NMBAs (Neuromuscular blocking agents) used? What is an example of an NMBA?

Answer 3

Specifically used in the context of surgery, endotracheal intubation or mechanical ventilation (to keep muscles from contracting so we can cut open).

Vecuronium (Norcuron) is an NMBA.

Question 4

What is the antagonist to Vecuronium (an NMBA)? What is its mechanism of action?

Answer 4

Acetylcholinesterase inhibitors (neostigmine). Inhibits the activity of acetylcholinesterase which metabolizes acetylcholine. Ach levels will rise and compete actively against Vecuronium.

Question 5

True or False. Neuromuscular blocking agents have an affect on the autonomic nervous system.

Answer 5

False. They bind to nicotinic-cholinergic receptors of the somatic nervous system, a different subtype than the ones found in the ANS.

Question 6

Which receptors are associated with the sympathetic division of the ANS? What neurotransmitter is associated?

Answer 6

Adrenergic receptors (alpha and beta). Norepinephrine.

Question 7

Which receptors are associated with the parasympathetic division of the ANS? What neurotransmitter is associated?

Answer 7

Muscarinic cholinergic receptors . Acetylcholine.

Question 8

True or False: Nicotinic Cholinergic receptors are only found in the parasympathetic division?

Answer 8

False. Nicotinic Cholinergic receptors are found in sympathetic and parasympathetic postganglionic neurons.

Question 9

Which organs and glands do not receive input from both branches of the ANS? Which input do they receive?

Answer 9

The arterioles. They only receive sympathetic input.

Question 10

True or False: sympathetic and parasympathetic input to organs is of equal strength.

Answer 10

False. One system will always predominate (typically the parasympathetic with bursts of sympathetic tone).

Question 11

Nicotininc cholinergic receptor antagonists (Autonomic Nervous System):

1. mechanism of action
2. outcome

Answer 11

1. inhibits both the smaller sympathetic input and the predominant parasympathetic input
2. results in a net sympathetic effect

Question 12

What would the effect of a nicotinic cholinergic receptor antagonist be on the heart?

Answer 12

The heart receives both sympathetic and parasympathetic input. The parasympathetic input predominates and slows the intrinsic rhythm. If a nicotinic cholinergic receptor antagonist is used, then the predominant parasympathetic input will be blocked, resulting in a net sympathetic effect. Therefore tachycardia will result.

Question 13

Why do we not longer use drugs that target nicotinic cholinergic receptors?

Answer 13

They result in a messy dose response curve because we are all a little different in which system predominates. The target is not as specific.

Question 14

Which receptors are found in the target tissues of the sympathetic division vs. the parasympathetic division.

Answer 14

Sympathetic - Adrenergic receptor

Parasympathetic - Muscarinic cholinergic receptor

Question 15

What are two other names for cholinergic drugs class?

Answer 15

Muscarinic agonists and parasympathomimetics.

Question 16

What effects do cholinergic drugs have?

Answer 16

stimulate smooth muscle (lungs, GI), stimulate gland secretions, decrease heart rate and force of contraction, constrict the pupil

Question 17

What are two other names for anticholinergic drug class?

Answer 17

Muscarinic antagonists and parasympatholytics.

Question 18

What effects do anticholinergic drugs have?

Answer 18

Opposite of cholinergics - Suppression of smooth muscle (lungs and GI), suppression of oral secretions, increased heart rate and force of contractions, pupil dilation.

Question 19

Direct acting cholinergic drugs vs. Indirect acting cholinergic drugs.

Answer 19

Direct acting cholinergic drugs bind to muscarinic cholinergic receptors whereas indirect acting inhibit acetylcholinesterase which causes an increase in acetylcholine. Ach levels rise systemically which means that it binds to receptors in the SNS as well as ANS.

Question 20

Clinical use of direct acting cholinergic drugs (Bethanechol).

Answer 20

• Bethanechol stimulates smooth muscle contraction via M3 receptors couple to Gq proteins.
• It is used to treat postoperative ileus and bladder atony
• drugs used in surgery can have negative effects on the gut and bladder and sometimes people require a kickstart with bethanechol

Question 21

Clinical use of indirect acting cholinergic drugs.

Answer 21

Myasthenia graivs and Alzheimer’s disease (Ach is important to memory at the level of the hippocampus) - Because these drugs affect autonomic gnaglia, muscarinic receptors, skeletal muscle and cholinergic receptors in the CNS, we only use them when we don’t have anything else.

Question 22

Which drug class are insecticides? What are the two types of insecticides and how do they differ?

Answer 22

Indirect acting cholinergic drugs.

Carbamate insecticides reversibly bind and the effects are often reverse 2-8 hours post exposure.

Organophosphate insecticides irreversibly bind and recovery requires synthesis of new enzymes (1-2 weeks).

Question 23

What can insecticides induce?

Answer 23

Cholinergic crisis.

Question 24

Explain a cholinergic crisis.

Answer 24

Nicotinic effects: muscle fasiculations and fatigue

Muscarinic effects (pro-parasympathetic): salivation, lacrimation, urination, diarrhea, dyspnea, bradycardia, sweating, pin-prick pupils

This pro-parasympathetic state happens early on and very quickly.

Question 25

Effects of muscarinic antagonists.

Answer 25

Inhibition of parasympathetic input to target organs, inducing similar effects to sympathetic nervous system activation.

Question 26

What is the antidote for high levels of acetylcholine?

Answer 26

Atropine

Question 27

Atropine:

1. mechanism of action
2. solubility
3. effects
4. clinical use

Answer 27

1. inhibits Ach binding at muscarinic receptors
2. highly lipid soluble
3. increased heart rate, bronchodilation, decreased GI motility, pupil dilation, decreased gland secretion
4. mydriatic (to dilate pupils - optometrists), treatment of carbamate insecticide poisoning, increaseing HR in shock patients, suppressing gastric and oral secretions in surgery patients

Question 28

What are some clinical uses of anticholinergic drugs?

Answer 28

Motion Sickness - Scopolamine

Bronchodilation: asthma & COPD - Ipratropium

Urinary urgency & incontinence - Oxybutynin & Tolterodine

Question 29

What are some clinical uses of anticholinergic drugs?

Answer 29

Motion Sickness - Scopolamine

Bronchodilation: asthma & COPD - Ipratropium

Urinary urgency & incontinence - Oxybutynin & Tolterodine

Question 30

What is another name for adrenergic agonists?

Answer 30

Sympathomimetics

Question 31

What is another name for adrenergic antagonists?

Answer 31

Sympatholytics

Question 32

What effects do adrenergic agonists have on the following receptors?

1. Alpha 1 receptors
2. Beta 1 receptors
3. Beta 2 receptors

Answer 32

1. constrict smooth muscle (blood vessels, uterus) and dilate pupils
2. increase heart rate and force of contraction, increase release of renin
3. inhibit smooth muscle (bronchioles, uterus)

Question 33

What effects do adrenergic antagonists have on the following receptors?

1. Alpha 1 receptor
2. Beta 1 receptor
3. Beta 2 receptor

Answer 33

1. relax smooth muscle (blood vessels, uterus) and constrict pupils
2. decrease heart rate and force of contraction, inhibit release of renin
3. activate smooth muscle contraction (bronchioles, uterus)

Question 34

True or False: There are no indirect acting drugs in the sympathetic division.

Answer 34

true

Question 35

When are adrenergic drugs generally used? What are the adverse effects associated with?

Answer 35

Significant effects for cardiovascular and respiratory diseases.

Adverse effects are associated with over-stimulation of the sympathetic nervous system (tachycardia, hypertension…).

Question 36

Which drug class would be used to treat anaphylaxis, shock or heart failure? What would the therapeutic effects be? What is an example of this type of drug?

Answer 36

Beta 1 receptor agonist. This would increase heart rate, contractility and cardiac output.
E.g. epinephrine

Question 37

Which drug class would be used to treat acute asthmatic bronchoconstriction? What would the therapeutic effects be? What is an example of this type of drug?

Answer 37

Beta 2 receptor agonist. Induces relaxation of bronchial smooth muscle.
E.g. salbutamol

Question 38

Which drug class would be used to treat hypotension and nasal congestion? What would the therapeutic effects be? What is an example of this type of drug?

Answer 38

Alpha 1 receptor agonist. Induces vasoconstriction.

E.g. Phenylephrine

Question 39

Which drug class treats preterm labour? What would the therapeutic effects be? What is an example of this type of drug?

Answer 39

Beta 2 receptor agonists. Induces relaxation of uterine smooth muscle.

E.g. terbutaline, ritodrine

Question 40

When are adrenergic antagonists generally used? What adverse effects are they associated with?

Answer 40

They have significant effects for hypertension. Adverse effects are associated with inhibition of the sympathetic nervous system (bradycardia, hypotension, etc.).

Question 41

What are the most widely prescribed class of autonomic drug?

Answer 41

Adrenergic antagonists.

Question 42

How do alpha-adrenergic antagonists decrease blood pressure?

Answer 42

Relax vascular smooth muscle.

Question 43

How do beta-adrenergic antagonists decrease blood pressure.

Answer 43

Decrease the heart rate and force of contraction of the heart and reduce the production of renin.

Question 44

Why do we generally choose beta- adrenergic antagonists over alpha-adrenergic antagonist?

Answer 44

Alpha adrenergic antagonists cause so much vasodilation that people get orthostatic hypotension.

Question 45

Which Beta-adrenergic antagonists are cardio-selective. Why do we generally choose these drugs for treatment?

Answer 45

Beta 1 receptor antagonists are cardio-selective. We use these because they don’t pose the risk of bronchoconstriction (specifically in patients with history of asthma or COPD).