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Pharmacology FoM > Pharmacology of ANS 2 > Flashcards

Pharmacology of ANS 2 Flashcards

1
Q

How is Acetylcholine synthesised and released?

A
  • When neuron stimulates, granules containing ACh fuse with membrane and ACh diffuses into synaptic cleft
  • ACh interacts with muscarinic or nicotinic receptors producing response in post-synaptic cell
  • Choline taken into neuron and acetylated
  • Synthesised in pre-synaptic nerve terminal
  • Acetyl coenzyme A
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2
Q

What toxin triggers the release of acetylcholine?

A
  • Black widow spider bite
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3
Q

How is acetylcholine broken down?

A
  • Rapidly broken down by membrane-bound enzyme acetylcholinesterase (AChE)
  • Choline reabsorbed at pre-synaptic terminal
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4
Q

What actions would drugs do that mimic ACh at muscarinic receptors?

A
  • Constriction of pupil and reduction in ocular pressure
  • Increased salivation
  • Reduced heart rate
  • Increased GI motility
  • Contraction of bladder
  • Sweating
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5
Q

What drugs mimic ACh at muscarinic receptors?

A
  • Pilocarpine- may be used as eye drops to treat glaucoma
  • Bethanechol- simulates muscle contraction and occasionally used in urinary retention or to stimulate return of normal GI function after anaesthesia
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6
Q

What happens when drugs block ACh muscirinic receptors?

A
  • Pupil dilation (mydriasis)
  • Reduced secretions
  • Increased heart rate
  • GI motility decreased
  • Urinary tract smooth muscle relaxed
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7
Q

What drugs block ACh muscarinic receptors?

A
  • Atropine- reduces secretions
  • Ipatropium- bronchodilator
  • Hyoscine- motion sickness or to facilitate endoscopy
  • Tropicamide- as eye drops to induce mydriasis
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8
Q

What occurs at the neuromuscular junction?

A
  • Somatic system utilises ACh but there are nicotinic 2 receptors on post-synaptic membrane
  • ACh broken down by acetylcholinesterase
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9
Q

How do drugs affect transmission at the neuromuscular junction

A
  • Those that act directly on muscarinic receptors do not affect NMJ
  • Drugs that affect synthesis, packaging, release or metabolism of ACh will affect both sympathetic and somatic
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10
Q

What drug prevents ACh release?

A
  • Botulinum toxin is poison isolated from clostridium botulinum
  • Inhibits ACh release and used to treat dystonia caused by stroke/cerebral palsy
  • Injected directly into affected muscle (so won’t cause general paralysis or affect ANS)
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11
Q

Give an example and use of a short acting anticholinesterase

A
  • Edrophonium

- Diagnosis of myasthenia gravis

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12
Q

Give an example and use of a medium duration anticholinesterase

A
  • Neostigmine

- Treatment of myasthenia gravis

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13
Q

Give an example and use of irreversible anticholinesterases

A
  • Organophosphates and poison gases like dyflos and Sarin

- Pesticides

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14
Q

What types of drugs are used to in the early stages of Alzheimer’s disease?

A
  • Drugs that inhibit AChE in the CNS

- Donepezil

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15
Q

Describe the synthesis and release of noradrenaline

A
  • When pre-synaptic neuron is stimulates, NA is released into synaptic cleft
  • NA interacts with adrenergic receptors on target tissue
  • Tyrosine taken up by pre-synaptic neuron and converted to NA and packaged into vesicles
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16
Q

What receptors are acetylcholine nicotinic?

A
  • Post-ganglionic parasympathetic

- Post-ganglionic sympathetic for sweat glands

17
Q

Which synapses have noradrenaline as the neurotransmitter?

A
  • Pre-ganglionic parasympathetic (cranial)

- Pre-ganglionic sympathetic (thoracic and lumbar)

18
Q

How is noradrenaline removed?

A
  • Free NA in cytosol of pre-synaptic cell is metabolised by monamine oxidase (MAO)
  • In ANS, most of NA in synapse is returned to pre-synaptic cell by specific transport mechanisms
  • Free NA in the synapse is also taken up by neighbouring cells and metabolised by catechol-O-methyl transferase (COMT)
19
Q

What drugs modify noradrenaline synthesis or reuptake?

A
  • Reserpine- blocks packaging of NA into the granules
  • Amphetamine- displaces NA from granules
  • Cocaine and some antidepressants- blocks reuptake of NA from synapse
20
Q

Which drugs block NA metabolism?

A
  • MAO inhibitors- first drug family used as antidepressants. Side effects- atropine-like effects- dry mouth, blurred vision
  • COMT inhibitors- may be used in Parkinson’s to prevent dopamine breakdown
21
Q

What drug actions would mimic NA actions on SNS- sympathomimetics?

A
  • Relaxation of smooth muscle
  • Tachycardia- increased heart rate and force
  • Decreased blood flow to skin and GI tract
  • Increased blood flow to muscles
22
Q

Which drugs mimic the actions of NA on the SNS?

A
  • Salbutamol- bronchodilator used in asthma and prevents premature labour
  • Adrenaline- added to local anaesthetics to reduce diffusion, also used in cardiac arrest
  • Dobutamine- stimulates the heart
23
Q

What would happen if a drug blocked NA actions on sympathetic nervous system (sympatholytics)?

A
  • Bradycardia- slowing of heart rate
  • Hypotension- reduced cardiac output
  • Increased blood flow to skin and GI tract
24
Q

Which drugs block the actions of NA on the sympathetic nervous system?

A
  • Propanolol- angina, hypertension and anxiety

- Prazosin- resistant hypertension and benign prostate hypertrophy

25
Q

What does activation of the sympathetic ns lead to?

A
  • Stimulation leads to release of noradrenaline from most sympathetic nerve endings
  • Also triggers release of adrenaline and noradrenaline from adrenal medulla
26
Q

What are the subdivisions of peripheral adrenoreceptors?

A
  • Peripheral adrenoreceptors are divided into alpha and beta subtypes
  • Further divided into alpha 1 and 2 and beta 1 and 2 subtypes
  • NA and A have distinct effects on these subtypes
27
Q

What stimulates alpha receptors but is less effective on beta receptors?

A

Noradrenaline

28
Q

What stimulates both alpha and beta receptors?

A

Adrenaline

29
Q

Where are alpha 1 adrenoreceptors found?

A

Blood vessels and smooth muscle

30
Q

Where are alpha 2 adrenoreceptors found?

A

Pre-synaptic cells and inhibit release of neurotransmitters

31
Q

Where are beta 2 adrenoreceptors found?

A

Bronchial and uterine smooth muscle

32
Q

Where are beta 1 adrenoreceptors found?

A

Heart where they increase rate AND force of contraction

Pharmacology FoM (12 decks)

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