Drugs affecting autonomic nervous system Flashcards
The nervous system consists of:
Central part (brain and spinal cord)
Peripheral part:
- somatic: conscious control of movement
- autonomic (vegetative): unconscious control
Characterize the autonomic nervous system (ANS):
- Control system: visceral functions, heart rate, digestion, respiration rate, salivation, perspiration, pupillary dilation, urination
- Involuntary
- Medulla oblongata in lower brainstem
The ANS is divided into two subsystems:
- Parasympathetic nervous system (slow down) - rest, digest, restore
- Sympathetic nervous system (speed up) - fight, fright, flight
Drugs acting on the ANS are divided into:
- Parasympathotropic agents
- Parasympathomimetics (cholinergic agonists)
- Parasympatholytics (cholinergic antagonists) - Sympathotropic agents
- Sympathomimetics (adrenergic agonists)
- Sympatholytics (adrenergic antagonists)
How does cholinergic and adrenergic drugs act?
Stimulating (mimetic activity) or blocking (lytic activity) receptors of the autonomic nervous system
On which receptord does parasympathotropic agents act?
cholinergic receptors
- acetylcholine is the neuroreceptor in this
part of CNS
Name two classes of cholinergic receptors:
- Muscarinic
- Nicotinic
Where are muscarinic receptors found and what do they do?
- smooth muscles of exocrine glands & in lungs –> hypersecretion
Where are nicotinic receptors found and what do they do?
- neuromuscular junctions of somatic muscles –> muscular contraction
Division of drugs with parasympathomimetic activity:
- Directly acting - bind to cholinergic receptors and act like acetylcholine
- Indirectly acting - inhibit degradation of acetylcholine by inhibiting enzyme acetylcholine esterase
Name directly acting drugs with parasympathomimetic activity:
acetylcholine
pilocarpine
muscarine
carbachol
metacholine
Name indirectly acting drugs with parasympathomimetic activity:
physostigmine
neostigmine
pyridostigmine
organophosphates
Function and examples of drugs with parasympatholytic activity:
inhibit function of the parasympathetic nervous system by acting as competitive antagonist of acetylcholine on muscarinic receptor
- atropine, scopolamine, homatropine, propanteline
What is atropine?
Competitive antagonist for muscarinic acetylcholine receptors.
Anticholinergic drug.
Uses of atropine:
- Cycloplegic in ophtalmogy (paralyze accomodation reflex)
- Mydriatic in ophtalmology (dilate pupils)
- Resuscitation (bradycardia)
- Premedication (inhibit secretion)
- Organophosphate poisoning
- Drug overdose
What is SLUDGE syndrome?
Drug overdose
- Salivation
- Lacrimation
- Urination
- Diaphoresis (sweating)
- Gastrointestinal motility
- Emesis
What is the effect of parasympathotropics on pupils?
Parasympatholytics - contraction of radial muscle fibres, mydriasis
Parasympathomimetics - contraction of circular muscle fibres, miosis
Explain the effect of parasympathotropic substances on smooth muscle of the iris:
Radial and circular muscle fibres enables increase or decrease of pupil.
Increase tonus of sympathetic NS after application of parasympatholytic drugs –> contraction of radial fibres - mydriasis.
Parasympathomimetic drugs –> contraction of circular muscle fibres - miosis.
Function of sympathotropic agents:
bind to adrenergic receptors
- adrenaline and noradrenaline are neurotransmitters
Division of sympathotropic agents:
Directly acting - act directly on adrenoreceptors
Indirectly acting - affect production, kinetics and degradation of mediators (noradrenalin and adrenalin)
Name sympatomimetic agents:
adrenaline
noradrenaline
dopamine
ephedrine
amphetamine
Name sympatholytic agents:
ergotamine
prazosine
propranolol
bisoprolol
esmolol
methyldopa
