parasympathetic nervous system

Question 1

where are nictotinic receptors located, and significance

Answer 1

between pre and post ganglionic neurones in ANS (or between neurone and adrenal medulla in one SNS pathway); present throughout so can affect all aspects of ANS

Question 2

what are nicotinic receptor antagonists also called

Answer 2

ganglion blocking drugs

Question 3

what 2 things do nicotinic receptor antagonists block

Answer 3

block actual receptor, or act as ion channel blockers (e.g. preventing Na+ influx)

Question 4

2 examples of nicotinic receptor antagonists

Answer 4

hexamethonium (blocks ion channel; anti-hypertensives), trimetaphan (blocks receptor; most common)

Question 5

what is a use-dependent block and to what type of antagonist does it apply to

Answer 5

use-dependent block: blocks ion channel incompletely, not receptor; more open channels are, more effective drug is; receptor block: more agonist, less effective antagonist; ion channel block: more agonist, more effective antagonist

Question 6

antagonist vs ion channel blocker affinity

Answer 6

antagonists have affinity to block receptor, but if in channel pore just physical blockade of pore

Question 7

slide 13

Answer 7

slide 13

Question 8

outcome of nicotinic recepor antagonist use

Answer 8

could block out all ANS; depends which system is dominant in that moment in time (if SNS dominant at time, that is the effect that is lost, and vice versa)

Question 9

outcome of increased SNS activity (at rest = dominant PSNS) due to nicotinic receptor antagonist use

Answer 9

pupil, trachea and bronchiole dilation; glycogenolysis and gluconeogenesis; lipolysis; increased renin secretion; detrusor relaxation and constriction of trigone and sphincter; thick, viscous secretions; piloerection and increased sweating; increased heart rate and contractility (at rest PSNS has more effect so this effect is lost, increasing heart rate); decreased GI motility and tone with sphincter contraction; dilation of skeletal muscle blood vessels; constriction of blood vessels innervating skin, mucous membranes and splanchnic area

Question 10

why do nicotinic receptor antagonists cause hypotension

Answer 10

heart, blood vessels, kidneys: heart rate will increase (PSNS dominant at rest), but dilation of blood vessels to GIT (SNS dominant at rest; decreased TPR) and stops renin secretion to kidney (SNS dominant at rest; reduced blood volume, Ang II and TPR)

Question 11

effect of nicotinic receptor antagonists on smooth muscle at rest

Answer 11

pupil dilation, decreased GI tone, bladder dysfunction, bronchodilation

Question 12

effect of nicotinic receptor antagonists on exocrine secretions

Answer 12

decrease secretions from salivary glands, GIT, skin and trachea and bronchioles

Question 13

what nicotinic receptor antagonist was the first anti-hypertensive

Answer 13

hexamethonium

Question 14

when is trimetaphan (nicotinic receptor antagonist) used

Answer 14

during surgery as an anti-hypertensive as short acting

Question 15

how does a-bungarotoxin work

Answer 15

covalently binds to receptor and must be replaced to restore function; designed to target skeletal muscle as binds to somatic nervous system nicotinic receptor at NMJ

Question 16

nicotinic receptor antagonists vs muscarinic receptor antagonists

Answer 16

nicotinic too messy and broad to be useful as effect all of autonomic function; muscarinic is more discrete so therapeutically more useful