Module 4d: vasoactive drugs

Question 1

What are the divisions of peripheral nervous system?

Answer 1

somatic: motor and sensory

Autonomic: sympathetic + parasympathetic

Question 2

What is the autonomic ns responsible for?

Answer 2

involuntary control of automatic body functions

Question 3

Describe the sympathetic division of ANS

Answer 3

Thoracolumbar outflow
Postganglionic postganglionic neurotransmitter is noradrenaline
Alpha + beta receptors

Question 4

Describe the parasympathetic division of ANS?

Answer 4

Craniosacral outflow
postganglionic neurotransmitter= Ach
Nicotinic and muscarinic receptors

Question 5

What is the first stage in the stress response?

Answer 5

Humoral activatiion with release of hormones:
- Defence of blood volume
- Increase aldosterone and ADH
- Mobilisation of glucose stores
- inhibits insulin

Question 6

What is the second stage of stress response?

Answer 6

Neural activation: haemodynamics:
- increased sympathetic outflow
- Blood flow increased to heart, lungs, brain and muscle
- Blood flow decreased to GIT, kidney, liver and skin

Question 7

What is the last response in stress response?

Answer 7

series of neurohumoral responses

Question 8

Which organs are supplied by ANS

Answer 8

Eye
Glands: Sweat &
Salivary
Heart
Lung
Stomach & GIT
Liver & Gallbladder
Bladder
Uterus
External genitalia

Question 9

What is the adrenal medulla made of?

Answer 9

specialised sympathetic ganglion with NO post ganglionic fibres

Post ganglionic fibres are secretory cells

Medulla secretes:
- noradrenaline(70%)
- adrenaline
- dopamine ( small amounts)

Question 10

What are the 2 neurotransmitters in ANS?

Answer 10

Ach- parasympathetic division
Noradrenaline- sympathetic division

Question 11

What are the 2 types of receptors in ANS?

Answer 11

Cholinergic- binds Ach
Noradrenergic: binds noradrenaline

Question 12

What is the distribution of cholinergic receptors in body?

Answer 12

all autonomic ganglia including adrenal medulla

all parasympathetic postganglionic nerve terminals

Sympathetic postganglionic nerve terminals in SWEAT GLANDS ONLY

Somatic NS- NMJ

Question 13

What cholinergic receptor subtypes do you get?

Answer 13

Nicotinic:
- skeletal NMJ + all autonomic ganglia
- Stimulated by nicotine and Ach
- Inhibited by neuromuscular blocking agents

Muscarinic:
- at parasympathetic postganglionic fibres
- stimulated by muscarine and Ach
- Inhibited by atropine and glycopyrrolate

Question 14

What are the signs of parasympathetic excess?

Answer 14

Blindness (ptosis)
Bronchial secretions
Bronchospasm
Bradycardias
“B”eristalsis (peristalsis) → diarrhoea, vomiting
Bile secretion
Bladder contraction

Question 15

What are the distribution and subtypes of adrenergic receptors?

Answer 15

Distribution: only found on sympathetic postganglionic nerve terminals

Subtypes:
Alpha:
- a1: post-synaptic: smooth muscle vasoconstriction
- a2: pre-synaptic: inhibits further NA release

Beta:
- B1: increased contractility, HR, AV node conduction
- B2: Increased skeletal muscle dilatation, bronchial relaxation, uterine relaxation

Question 16

How does neostigmine works

Answer 16

It stimulates the PNS by blocking AchE. Increases Ach and will displace neuromuscular blocking agents= facilitating reversal of drugs.

Question 17

How does neostigmine cause side effects?

Answer 17

Build up of Ach (parasympathetic stimulator) leads to parasympathetic effects

Question 18

How does muscarinic blockade of PNS work?

Answer 18

postganglionic PNS receptors are muscarinic and blocked-> blocks muscarinic effects (e.g. atropine, glycopyrrolate)

Question 19

What are B1 agonists named and what do they do?

Answer 19

They are called inotropes and increases force of contraction

Question 20

What are a1 agonists named and what do they do?

Answer 20

They are called vasopressers and raises BP

Question 21

Which 2 neurotransmitters are inotropes and vasopressors?

Answer 21

Adrenaline(all a +b) and NA(a1,a2,B1)

Question 22

What neurotransmitter is a vasopressor but not an inotrope?

Answer 22

phenylephrine (a1 only)

Question 23

What other neurotransmitter is also an inotrope

Answer 23

dobutamine

Question 24

Which neurotransmitter releases NA from the sympathetic terminals as well as directing a +B effects

Answer 24

Ephedrine

Question 25

What will be given to get a1 agonist only?

Answer 25

Phenylephrine

Question 26

What will be given to get only a2 agonist?

Answer 26

Clonidine
Dexmedetomidine

Question 27

What will be given for both B1+ B2 effects

Answer 27

Isoprenaline

Question 28

What will be given for B2 effects?

Answer 28

Salbutamol

Question 29

What are alpha receptor antagonists/blockers do and give 3 examples?

Answer 29

antihypertensives

Examples:
- Phentolamine-a1 + a2
- Phenoxybenzamine- a1 non-competitive
- Prazosin + doxazosin-a1

Question 30

What does all B-blockers do?

Answer 30

competetive with varying B1 + B2 effects
Bradycardia, antiarrythmics, sedative, lower BP
Decrease cardiac mortality
Bronchospasm in asthmatics
Inhibit gluconeogenesis in liver and lipolysis

Question 31

What is an example of alpha + beta blocker?

Answer 31

Labetalol-predominantly B blocker

Question 32

What are the vasopressors used and when do you use them?

Answer 32

1. Ephedrine: management of hypotension, raises BP + gives tachycardia(Beta effects dominate)
2. Phenylephrine: vasopressor in obstetric spinal anaesthesia. Extremely potent a1 agonist. MUST BE DILUTED

Question 33

When are inotropes used?

Answer 33

critically ill patients who need inotropic support(sepsis/ccf)

Given via central line