1. Intro to ANS

Question 1

what autonomic system controls pupillary constriction?

Answer 1

parasympathetic system

Question 2

what autonomic system controls cephalic (secretions) and gastric (motility/secretions) phases of gastric secretion and via which nerve?

Answer 2

parasympathetic system via the vagus nerve

Question 3

what autonomic system is the heart mainly controlled by?

Answer 3

parasympathetic (vagal) system

Question 4

what happens to baroreceptor firing if BP falls?

Answer 4

baroreceptor firing goes down, decreasing the stimulation of the parasympathetic system and decreasing the inhibition of the sympathetic system so BP rises

Question 5

which autonomic system is involved in the liver and which processes occur as a result of stimulation?

Answer 5

sympathetic nervous system stimulating an increase in gycogenolysis and gluconeogenesis

Question 6

in the parasympathetic system which ganglionic fibre is shorter and which is longer?

Answer 6

pre-ganglionic fibre is longer and post-ganglionic fibre is shorter

Question 7

where do parasympathetic pre-ganglionic fibres originate?

Answer 7

brain (cranal) and spine (sacral)

Question 8

where do sympathetic pre-ganglionic fibres originate?

Answer 8

spinal cord (thoracolumbar)

Question 9

describe the nature of the parasympathetic pathway

Answer 9

discrete/localised with little divergence (1:1 pre vs post ganglionic fibres)

Question 10

describe the nature of the sympathetic pathway

Answer 10

coordinated response that is very divergent (up to 1:20 pre vs post ganglionic fibres)

Question 11

what are sensory neurones in the enteral nervous system connected to?

Answer 11

mucosal chemoreceptors and stretch receptors

Question 12

what do mucosal chemoreceptors and stretch receptors detect?

Answer 12

chemical substances in the gut lumen

tension in the gut wall caused by food

Question 13

where is information from the enteral nervous system relayed to?

Answer 13

submucosal (Meissner’s) and myenteric (Auerbach’s) plexuses via interneurons

Question 14

what do motor neurones in the enteral nervous system release?

Answer 14

ACh or substance P to contract smooth muscle

vasoactive intestinal peptide or NO to relax smooth muscle

Question 15

how is the somatic nervous system different from the autonomic nervous system?

Answer 15

it involves one motor neurone projecting from the spinal cord to skeletal muscle where ACh is released which stimulates skeletal muscle contraction

Question 16

where are nicotinic receptors found and what are they stimulated by?

Answer 16

at all autonomic ganglia between pre and post ganglionic fibres

stimulated by nicotine/ACh

Question 17

what type of receptors are nicotinic receptors and what is their speed?

Answer 17

ionotropic receptors that are linked to ion channels

fast

Question 18

where are muscarinic receptors found and what are they stimulated by?

Answer 18

at all effector organs innervated by parasympathetic post-ganglionic fibres or when the effector organ is a sweat gland

stimulated by muscarine/ACh

Question 19

what type of receptors are muscarinic receptors and what is their speed?

Answer 19

G-protein coupled receptors

slow

Question 20

what are the subtypes of muscarinic cholinoceptors?

Answer 20

*M1 - neural
*M2 - cardiac
*M3 - exocrine and smooth muscle
M4 - periphery
M5 - striatal dopamine release

Question 21

where are adrenoreceptors found and what are they stimulated by?

Answer 21

at all effector organs innervated by sympathetic post-ganglionic fibres

stimulated by NA/Adrenaline

Question 22

what type of receptors are adrenoreceptors and how do these receptors work?

Answer 22

G-protein coupled

an agonist binds to the receptor causing G-protein activation. A 2nd messenger is generated which activates cell signalling

Question 23

list the steps involved in the synthesis of neurotransmitters

Answer 23

1. NT produced by precursor via enzymatic conversion
2. NT packaged into vesicles
3. an action potential causes calcium influx that promotes the exocytosis of the NT
4. vesicle fusion - NT is released into the synapse
5. the NT reacts with the receptor
6. the receptor transduces the response
7. degradation of NT
8. reuptake

Question 24

what are the precursors of ACh and what enzyme converts them to ACh?

Answer 24

Acetyl-CoA (from glucose metabolism) and choline (from diet)

enzymatic conversion by choline acetyl transferase (byproduct is CoA)

Question 25

what does acetylcholinesterase break ACh into?

Answer 25

choline and acetate

Question 26

what would happen if acetylcholinesterase was blocked? Give an example of a substance that blocks it

Answer 26

build up of ACh in the synaptic cleft causing a prolonged effect on the post-ganglionic neuron, eventually leading to decreased responsiveness of the receptors at neuromuscular junctions and paralysis

e.g. botulinum toxin interferes with ACh exocytosis

Question 27

How is NA formed in the pre-synaptic vesicle?

Answer 27

1. tyrosine is converted to DOPA by tyrosine hydroxylase
2. DOPA is converted to dopamine by DOPA decarboxylase
3. dopamine is packaged into vesicles with dopamine b hydroxylase to form NA

Question 28

how is adrenaline formed from NA?

Answer 28

NA is converted to adrenaline by phenylethanolamine methyl transferase (PNMT) (methylation)

Question 29

how is adrenaline different to NA

Answer 29

NA is produced by neurones whereas adrenaline is produced in chromaffin cells (stimulated by ACh)

Question 30

what are the 2 methods of NA reuptake?

Answer 30

1. uptake into the pre-synaptic nerve terminal and metabolised by Monoamine Oxidase A (MAO-A)
2. uptake by the extraneuronal tissue and degraded by COMT

Question 31

what is the rate limiting enzyme in the production of NA?

Answer 31

tyrosine hydroxylase which generates DOPA from tyrosine

Question 32

what increases the production of PNMT?

Answer 32

cortisol upregulates the medulla’s ability to produce adrenaline as the corticosteroids pass through the adrenal medulla

Question 33

where is adrenaline released into?

Answer 33

the extracellular space where it eventually enters the bloodstream