PT2: Pharmacology of Autonomic Nervous System

Question 1

what is the function of the autonomic nervous system

Answer 1

contraction and relaxation of smooth muscle in blood vessels and organs
regulation of glandular secretion (exocrine and some endocrine)
control of heart rate
metabolism

Question 2

what organs have both sympathetic and parasympathetic action

Answer 2

smooth muscle of gut and bladder
heart
airways

Question 3

what organs only have sympathetic action

Answer 3

sweat glands

blood vessels

Question 4

what organs only have parasympathetic action

Answer 4

ciliary muscles of the eye

Question 5

what are the two neuron types involved in sympathetic and parasympathetic action

Answer 5

pre- and post-ganglionic

Question 6

what are the features of a preganglionic neuron

Answer 6

cell body in the CNS, small diameter and myelinated, synapses at autonomic ganglia, preganglionic fibres release ACh which acts on nicotinic receptors in the post-synaptic neuron

Question 7

what neurotransmitter do preganglionic fibres release

Answer 7

ACh

Question 8

which receptors does ACh act on

Answer 8

nicotinic

Question 9

what are the features of a postganglionic neurone

Answer 9

cell body in autonomic ganglion, small diameter and unmyelinated, synapse close to target organ

Question 10

what are the is considered to be a specialised ganglion

Answer 10

adrenal medulla

Question 11

what are considered to be specialised post-synaptic neurons

Answer 11

chromaffin cells

Question 12

what is the primary transmitter between pre- and post-ganglionic neurons

Answer 12

ACh

Question 13

what ganglion type do most actions occur via

Answer 13

nicotinic ACh receptors

nAChR

Question 14

what are the three classes of nicotinic receptors

Answer 14

muscle, neuronal (CNS), neuronal (autonomic ganglion)

Question 15

what are nicotinic receptors

Answer 15

ligand gated ion channels that generate a fast excitory post synaptic potential
most ganglia are innervated by several preganglionic nerve fibres - simultaneous firing required to generate action potential

Question 16

what are the features of nicotinic receptors in autonomic ganglia

Answer 16

ligand gated ion channel, containing alpha3 subunit, cation channel (NA+ in, K+ out; fast EPSP)
when threshold potential is reached an action potential is generated in post-ganglionic cell

Question 17

via what receptors does primary ganglionic signalling occur

Answer 17

ACh acting on nicotinic receptors

Question 18

how do M1 muscarinic receptors on post-synaptic bodies modulate signal

Answer 18

K+ channels closing, slow excitatory PSP (epsp)

Question 19

how do M2 muscarinic receptors on post-synaptic bodies modulate signal

Answer 19

increased K+ conductance, hyperpolarisation, slow inhibitory PSP (ipsp)

Question 20

what is released from preganglionic fibres during transmission

Answer 20

neuropeptide co-transmittors

late slow EPSP

Question 21

what are the physiological consequences of nicotinic receptor stimulation (periphery)

Answer 21

stimulation of voluntary muscle (somatic system)
stimulation of autonomic ganglia (sympathetic and parasympathetic)
secretion of adrenaline from the adrenal medulla

Question 22

what neurotransmitter do most postsynaptic sympathetic fibres release

Answer 22

noreadrenaline

exceptions are sweat glands (ACh) and renal vessels (dopamine)

Question 23

what neurotransmitter do postsynaptic parasympathetic fibres release

Answer 23

ACh (to act on muscarinic receptors)

Question 24

what is the sensory nerve pathway in the airway

Answer 24

vagal sensory afferent nerve -> CNS -> vagal afferent nerve -> airway smooth muscle -> airway constriction

Question 25

what is the pathway of cholinergic signalling

Answer 25

parasympathetic nerve -> (airway) ACh -> M3, Gq and PLS receptors on airway smooth muscle, causing contraction

Question 26

what inhibits neuronal ACh release

Answer 26

M2 receptor feedback

M2 receptor on parasympathetic nerve

Question 27

what neurotransmitter do most postsynaptic fibres release

Answer 27

noreadrenaline

Question 28

what is the function of noreadrenaline

Answer 28

synthesised, stores and released from sympathetic nerves

very sparse sympathetic innervation of the airways and sympathetic control via circulating adrenaline (from adrenals)

Question 29

how selective are adrenoreceptors

Answer 29

relatively unselective (similar affinity) for two endogenous adrenergic neurotransmitters (adrenaline and noreadrenaline)

Question 30

what receptors do noreadrenaline and adrenaline activate

Answer 30

both alpha and beta adrenoreceptors
adrenaline more potent at b2 and a2
noreadrenaline more potent at a1 and b1

Question 31

what is the function of the a1 adrenoreceptor

Answer 31

constrict smooth muscle (except in GI where it relaxes)

Question 32

what is the function of the a2 adrenoreceptor

Answer 32

presynaptic inhibition of neurotransmitter release (sympathetic and parasympathetic neurones)

Question 33

what is the function of the b1 adrenoreceptor

Answer 33

increases heart rate and force of constriction

Question 34

what is the function of the b2 adrenoreceptor

Answer 34

dilates/relaxes smooth muscle

Question 35

what is the function of the b3 adrenoreceptor

Answer 35

thermogenesis in skeletal muscle

Question 36

what are co-transmitters

Answer 36

neurotransmitters released from the same neurones as ACh/NA

involved in pre- and post-synaptic modulation

Question 37

what does NANC transmitter stand for

Answer 37

non-adrenergic non-cholinergic transmitters

Question 38

what are three examples of NANC transmitters

Answer 38

ATP, neuropeptides, NO