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Basic Pharmacology > 11. Peripheral Nervous System > Flashcards

11. Peripheral Nervous System Flashcards

1
Q

2 systems in the PNS

A
  • afferent
  • efferent
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2
Q

Afferent systems contain …

A

sensory nervous systems

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3
Q

Efferent systems contain …

A
  • autonomic nervous system (controls smooth muscle/outside the influence of voluntary control)
  • somatic nervous system (voluntary motor control of skeletal muscle)
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4
Q

Functions in the sympathetic autonomic nervous system

A
  • pupils dilate
  • lens of eye adjusts for far vision
  • airways in lungs dilate
  • heart rate increases
  • respiratory rate increases
  • salivary secretions reduced
  • blood vessels to limb muscles dilate and those to visceral organs constrict
  • brain activity alertness
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5
Q

Functions of parasym autonomic nervous system

A
  • pupils constrict
  • lens of eye readjust for closer
  • airways in lungs constrict
  • resp rate decreases
  • heart rate decrease
  • blood vessels to limb muscles constrict and blood vessels to visceral organs more dilated
  • salivary secretions normalise and brain activity normalise
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6
Q

Main transmitters for preganglionic fibres in PNS for
- parasym
- sym
- somatic

A
  • acetylcholine
  • acetylcholine
  • none
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7
Q

Main transmitters for postganglionic fibres in PNS for
- parasym
- sym
- somatic

A
  • acetlycholine
  • noradrenaline
  • none
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8
Q

Main transmitters for NMJ fibres in PNS for
- parasym
- sym
- somatic

A

none
none
acetylcholine

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9
Q

What do we need to know about acetylcholine neurotransmission?

A
  • fundamentals of neurotransmission
  • synthesis, storage, release, receptor interaction, termination
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10
Q

ACh synthesises what?
Stored in …
Released by …
Receptor interactions?
Termination?

A
  • choline/choline acetyl transferase
  • vesicles
  • exocytosis
  • muscarinic/nicotinic
  • in synapse by acetylcholine esterase
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11
Q

2 main classes of ACh receptors

A
  • muscarinic
  • nicotinic
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12
Q

There are at least … main mACh receptor subtypes

A

3
M1,2,3

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13
Q

Muscarinic receptors are located where …

A

postganglionic parasympathetic synapses

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14
Q

Muscarinic receptors are … receptors

A
  • G-protein coupled or metabotropic
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15
Q

There are … main subtypes of nicotinic receptors

A

2
- neuronal type - brain and autonomic ganglia (excitatory)
- muscle-type - neuromuscular junction (excitatory)

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16
Q

What type of receptors are nicotinic receptors?

A
  • ligand gated ion channels or ionotropic
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17
Q

How does ACh act in sympathetic system?

A
  • acts on nicotinic receptor on preganglionic fibre
  • goes along postganglionic to heart
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18
Q

How does ACh react in parasym system?

A
  • long preganglionic fibre
  • acts on nicotinic receptor at ganglion then postganglionic fibre
  • acts on muscarinic receptor in heart
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19
Q

How does ACh work in somatic system?

A
  • acts on nicotinic receptors at target
20
Q

Muscarinic receptors mainly mediate …

A

parasympathetic effects

21
Q

Parasympathetic activation

A
  • pupils constrict
  • lens of eye adjusts to closer vision
  • airways in lungs constrict
  • heart rate decreases
  • blood vessels to limb muscles constrict
  • blood vessels to visceral organs more dilated
  • salivary secretions normalise
22
Q

Effects of muscarinic agonists

A
  • increased pupil constriction - contraction of constrictor pupillary muscles
  • decreased focal length of lens (contraction of ciliary muscles)
  • bronchoconstriction
  • decreases cardiac output (rate and force)
  • increased GI motility
  • increased exocrine gland secretion (sweating, salivation, bronciol secretion)
23
Q

Muscarinic agonsists are also known as …

A

parasympathomimetics

24
Q

Effect of muscarinic antagonists

A
  • pupils dilate (relaxation of constrictor pupillary muscle - blurred vision)
  • increased focal length of lens (relaxation of ciliary muscle)
  • bronchodilation
  • increased cardiac output (rate and force)
  • decreased GI motility
  • decreased exocrine gland secretion (dry mouth, decreased sweating)
25
Q

Muscarinic antagonists are also known as …

A

parasympatholytic

26
Q

Give 2 muscarinic receptor agonists

A
  • pilocarpine
  • carbachol
27
Q

Clinical uses of pilocarpine

A
  • treat glaucoma
  • local application causes ciliary muscle contraction - focus on near vision and increase drainage of aqueous humour
  • contraction of sphincter muscle causes pupil constriction
    OR
  • treat xerostomia
  • dry mouth/reduced saliva secretion can happen due to radiation, antineoplastic drugs, side effect of other drugs
  • take it to stimulate saliva secretions systemically - side effects of muscarinic-sweating, nausea, miminal cardiovascular side effect due to low dose
28
Q

Explain clinical use of muscarinic receptor antagonist

A
  • pupils dilation in eye surgery - causes pupil dilation (tropicamide 2-6 hrs compared to 6 days of atropine)
  • decrease oral/respiratory secretions before oral procedures and adjunct to anaesthesia (atropine/belladonna, deadly nightshade or glycopyrronium)
  • resuscitation in bradycardia to increase heart rate (atropine)
  • asthma to cause bronchodilation - ipratropium by inhalation
  • motion sickness - orally to decrease gastric motility - hyoscine
29
Q

Use of deadly nightshade - atropa belladonna

A
  • cosmetics over 2000 years ago
  • pupils dilate and make you more fit
30
Q

Neuronal nicotinic receptors are located where?

A
  • sympathetic and parasympathetic ganglia
31
Q

Agonists on neuronal nicotinic receptors activate what?

A
  • both sympathetic (vasoconstriction, tachycardia, hypertension) and parasympathetic (bradycardia, hypotension, increases GIT motility and secretion) systems
32
Q

Effect of agonists of neuronal nicotinic receptors

A
  • autonomic confusion
  • no clinically useful - ganglionic /neuronal nicotinic agonists
33
Q

Antagonists of neuronal nicotinic receptors do what? Example?

A
  • hexamethonium
  • loss of sym and parasym reflexes especially cardiac
  • not of great therapeutic use
34
Q

Muscle type nicotinic receptors are located where?

A

NMJ

35
Q

Stimulation of nicotinic receptors by ACh does what?

A
  • depolarisation
  • in muscle fibre known as end plate potential and contraction of skeletal muscle fibre
36
Q

Agonist and antagonist of muscle type nicotinic receptors

A
  • suxemethonium
  • tubocurarine
37
Q

Effects of nicotinic agonists at NMJ

A
  • initial depolarisation/EPP and muscle fibre contraction (muscle twitch)
  • because synthetic agonist is not metabolised rapidly by acetylcholinesterase, the fibre is persistently depolarised resulting in loss of further electrical excitability - known as depolarising block
  • paralysis/muscle relaxation for surgery (depolarising block)
38
Q

Effect of nicotinic antagonists at NMJ

A
  • hyperpolarisation
  • inhibition of EPPs
  • muscle fibre relaxation
  • paralysis for surgery
  • non-depolarising surgery
39
Q

ACh release is inhibited by …
Result?

A
  • botulinum toxin and bungarotoxin
  • causes autonomic and motor paralysis if injected
40
Q

Role of botulinum toxin

A
  • injected locally to treat muscle spasm
  • and in plastic surgery/botox
41
Q

What enzyme metabolises ACh?

A

acetylcholinesterase

42
Q

How to inhibit ACh metabolism?

A
  • anticholinesterases
  • increases ACh transmission
43
Q

Give 2 anticholinesterases

A
  • neostigmine
  • organophosphates
44
Q

Effects of anticholinesterases on autonomic nervous system

A
  • reflect increased transmission at parasympathetic postganglionic synapses
  • increases secretions, bradycardia, hypotension, pupil constriction
45
Q

Effects of anticholinesterases on NMJ

A
  • increased muscle tension and twitching
  • large doses cause depolarising block
  • neostigmine can treat myasthenia gravis (autoimmune disease, circulating antibodies against nicotinic receptors)

Basic Pharmacology (16 decks)

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