L5 - Autonomic Nervous System 1

Question 1

Breifly describe the structure of the ANS?

Answer 1

There’s 2 divisions: parasympathetic (PNS) and sympathetic (SNS).
PNS - pre-ganglionic nerves come from cranial or sacral nerves… post-ganglionic nerves release acetylcholine onto muscarinic receptors.
SNS - pre-ganglionic nerves come from thoracic or lumbar nerves…post-ganglionic nerve release noradrenaline onto adrenergic receptors (α and β)

Question 2

How do postganglionic nerves of the ANS release neurotransmitters onto effector organs?

Answer 2

They enter the effector organs and form varcosities which contain neurotransmitters. These are released upon nerve action potential, which then activates receptors on the effector organs, inducing a response.

Question 3

Where are M2 and M3 (muscarinic receptors) located, and when activated, what do they do?

Answer 3

M2 - heart, decreases heart rate

M3 - smooth muscle & glands, contract and secrete fluids

Question 4

Where can we find α1 adrenoceptors, and what do they do when activated?

Answer 4

In vascular smooth muscle. When they’re activated they contract

Question 5

Where are the 3 β-adrenoceptors located, and when activated what to they do?

Answer 5

β1 - Heart, increases heart rate and force of contraction
β2 - Smooth muscle, relaxation
β3 - Fat

Question 6

What are some of the mechanisms by which drugs modulate ANS function?

Answer 6

Drugs can affect the ANS by:

1. increasing or decreasing the levels of neurotransmitter
2. activating neurotransmitter receptors
3. blocking neurotransmitter receptors

Question 7

What are adrenoceptor agonists?

Answer 7

They bind to and activate adrenoceptors, e.g. adrenaline, phenylephrine, salbutamol

• Other names: sympathomimetics or adrenomimetics (note the word “mime” = to copy)
• Can target one or more of the 5 subtypes

Question 8

What do the direct effects of a given adrenoceptor agonist depend on?

Answer 8

1. receptor selectivity of the drug
2. adrenoceptor profile of the cell
3. cellular response to receptor activation

Question 9

Name a selective α1 adrenoceptor agonist and describe its effect.

Answer 9

Phenylephrine - primary effect = vasoconstriction.

used to decongest nasal passage by constricting blood flow

Question 10

Name a selective β2 adrenoceptor agonist and describe its effect.

Answer 10

Salbutamol (known as ‘Ventolin’) - causes relaxation of smooth muscle of airways. (it relieves bronchoconstriction)

Question 11

Name a selective α1 adrenoceptor antagonist and describe its effect.

Answer 11

Prazosin - reverses α1-mediated contraction of vascular smooth muscle causing vasodilation and lowers blood pressure.

Question 12

Name a non-selective β adrenoceptor antagonist and describe its effect.

Answer 12

Propranolol - binds to and inhibits both β1 and 2.
β1 - decreases heart rate and contractility, reducing cardiac output and blood pressure.
β2 - exacerbate bronchoconstriction

Question 13

Name a selective β1 adrenoceptor antagonist and describe its effect.

Answer 13

Metoprolol - decreases heart rate and contractility, reducing cardiac output and reduce blood pressure

Question 14

What are some desirable pharmacodynamic actions of β-blockers?

Answer 14

β blockers are not all the same - there are vasodilatation effects, antioxidant activity, K+-channel blockade, partial agonist activity, and membrane stabilising activity.

Question 15

Are Beta-1 receptors activated by noradrenaline, or adrenaline?

Answer 15

Noradrenaline. Beta-2 are activated by adrenaline