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YR2 LCRS Pharmacology > 1. Intro to ANS > Flashcards

1. Intro to ANS Flashcards

1
Q

what autonomic system controls pupillary constriction?

A

parasympathetic system

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2
Q

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

A

parasympathetic system via the vagus nerve

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3
Q

what autonomic system is the heart mainly controlled by?

A

parasympathetic (vagal) system

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4
Q

what happens to baroreceptor firing if BP falls?

A

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

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5
Q

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

A

sympathetic nervous system stimulating an increase in gycogenolysis and gluconeogenesis

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6
Q

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

A

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

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7
Q

where do parasympathetic pre-ganglionic fibres originate?

A

brain (cranal) and spine (sacral)

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8
Q

where do sympathetic pre-ganglionic fibres originate?

A

spinal cord (thoracolumbar)

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9
Q

describe the nature of the parasympathetic pathway

A

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

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10
Q

describe the nature of the sympathetic pathway

A

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

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11
Q

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

A

mucosal chemoreceptors and stretch receptors

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12
Q

what do mucosal chemoreceptors and stretch receptors detect?

A

chemical substances in the gut lumen

tension in the gut wall caused by food

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13
Q

where is information from the enteral nervous system relayed to?

A

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

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14
Q

what do motor neurones in the enteral nervous system release?

A

ACh or substance P to contract smooth muscle

vasoactive intestinal peptide or NO to relax smooth muscle

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15
Q

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

A

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

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16
Q

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

A

at all autonomic ganglia between pre and post ganglionic fibres

stimulated by nicotine/ACh

17
Q

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

A

ionotropic receptors that are linked to ion channels

fast

18
Q

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

A

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

stimulated by muscarine/ACh

19
Q

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

A

G-protein coupled receptors

slow

20
Q

what are the subtypes of muscarinic cholinoceptors?

A

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

21
Q

where are adrenoreceptors found and what are they stimulated by?

A

at all effector organs innervated by sympathetic post-ganglionic fibres

stimulated by NA/Adrenaline

22
Q

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

A

G-protein coupled

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

23
Q

list the steps involved in the synthesis of neurotransmitters

A
  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
24
Q

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

A

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

enzymatic conversion by choline acetyl transferase (byproduct is CoA)

25
Q

what does acetylcholinesterase break ACh into?

A

choline and acetate

26
Q

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

A

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

27
Q

How is NA formed in the pre-synaptic vesicle?

A
  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
28
Q

how is adrenaline formed from NA?

A

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

29
Q

how is adrenaline different to NA

A

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

30
Q

what are the 2 methods of NA reuptake?

A
  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
31
Q

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

A

tyrosine hydroxylase which generates DOPA from tyrosine

32
Q

what increases the production of PNMT?

A

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

33
Q

where is adrenaline released into?

A

the extracellular space where it eventually enters the bloodstream

YR2 LCRS Pharmacology (32 decks)

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