parasympathetic nervous system Flashcards
whats the sympathetic nervous system
fight or flight
whats the parasympathetic nervous system
rest and digest
somatic nervous system target organs
skeletal muscle
parasympathetic and sympathetic nervous systems target organs
- smooth muscle
- glands
- cardiac muscle
nicotinic ACh receptors at neuromuscular junction, are they affected by curare
yes
nicotinic ACh receptors in nervous system, are they affected by curare
no
muscarinic ACh receptors, what kind of cascade do they activate
G protein cascade
where do M1 and M3 have their effects
stomach, glands and bronchial smooth muscle, eye ciliary muscle, vascular endothelium
M1 and M3 effect on stomach, glands, bronchial smooth muscle, eye ciliary muscle
excitation
M1 and M3 effects on vascular endothelium
inhibition
M2 where does it have its effects
heart
M2 effect on heart
inhibition
antagonist of muscarinic ACh receptors
atropine
M2 effects bc of inhibition on heart
- bradycardia
- bronchoconstriction
- myosis
- salivation
- vomiting
- diarrhoea
- urination
two types of drugs acting on parasympathetic nervous system
- parasympathomimetics
- parasympatholytics
parasympathomimetics effects what parts of the eye
- iris spincter
- lacrimal glands
- intraocular pressure
parasympathomimetics effects on cardiovascular system
- negative chronotropic effects
- level of contraction not influenced
- vasodilation -> NO
parasympathomimetics effects on GI tract
- smooth muscle contraction
- glandular hyperfunction
- vomiting, diarrhoea
parasympathomimetics effects on resp tract
bronchoconstriction and increased bronchial secretion
parasympathomimetics effects on urinary tract
- bladder contraction
- sphincter-relaxation
where do direct parasympathomimetics bind
ACh receptors
where do indirect parasympathomimetics bind
ACh-esterase enzyme inhibition -> ACh-degradation is reduced
direct parasympathomimetics
- acetylcholine
- carbachol
- bethanechol
- methacholine
- pilocarpine
acetylcholine features
- non specific
- non selective - muscarinic and nicotinic
- very short half life
- not used therapeutically
carbachol features
- non specific to M-ACh receptors
- excellent activity
- pig emetic, laxative in the past
how is carbachol used nowadays
- exclusively locally
- in the uterus in the case of metritis
- in therapy of glaucoma as an eye drop
which direct parasympathomimetics are mainly used in human practise
- bethanechol
- methacholine
bethanechol features
- M-ACh specific
- induction of intestinal peristalsis after operations
- urinary bladder atony
methacholine features
- M-ACh specific
- cardiovascular system - atrial fibrillation
- pronounced peripheral vasodilation -> ergot toxicosis
whats pilocarpine
natural alkaloid of pilocarpus jaborandi
how was pilocarpine used earlier
had an important role in opthalmology
uses for pilocarpine in opthalmology
- glaucoma therapy - myosis after 15min
- KCS - effect ambigious
pilocarpine side effects
mild after local administration
indirect parasympathomimetics mechanism of action
inhibitors of ACh-esterase enzyme -> ACh levels are incr in the synapses-> various N-ACh and M-ACh effects and side effects
indirect parasympathoimetics side effects
- primarily on nicotinic ACh receptors
- furthermore on muscarinic ACh receptors
- on ACh receptors in CNS
duration of inhibition of AChE
1-6hrs
list of indirect parasympathomimetics
-physostigmine
-neostigmine
-pyridostigmine
-edrophonium
-organophosphates
-
physostigmine features
- contains tertiary nitrogen -> lipophilic -> kinetics
- very small therapeutic index systematically
- eye drop -glaucoma treatment
neostigmine features
- quaternary nitrogen -> less lipophilic -> kinetics
- eye drop, treatment of glaucoma
- given systemically is safer
neostigmine given systemically, IV, IM effects
- mysathema gravis treatment
- suspending the action of non-depolarising muscle relaxants
- incr intestinal motility
- induce emesis
edrophonium features
- competitive inhibition in neuromuscular junction -> action suspended by diffusion
- short effect - 5-15mins
test used to diagnose myasthenia gravis diagnosis
tensilon-test
organophosphates features
- irreversible inhibitors of AChE
- ectoparasiticides
- in humans treatment of glaucoma
organophosphates antidotes
- atropine
- pralidoxime
what is atropine
a tropane alkaloid, a parasympatholytic drug
0.5mg/kg atropine dose symptoms
mouth dryness, decr perspiration
1mg/kg atropine dose symptoms
tachycardia, mydriasis
2mg/kg atropine dose symptoms
accomodation, disturbances
5mg/kg atropine dose symptoms
constipation
10mg/kg atropine dose symptoms
ataxia, excitation, hallucination, delirium, coma
atropine effects on eye
- cycloplegia
- mydriasis
cycloplegia caused by atropine
m. ciliaris paralysis and lack of accomodation -> decr pain in keratitis, uveitis
mydriasis caused by atropine
m. constrictor pupillae inhibition, m dilator pupillae dilates the pupil -> diagnostic examination fo the eye, in uveitis the prevention of synechiae
atropine effects on cardiovascular system
lifting the cholinergic blockade of the heart
-tachycardia
what was atropine used for in the past
premedication
atropine effects on GI tract
- hyposalivation - important in premedication
- transit time incr
- constipation
- stomach acid secretion decr in higher doses
atropine effects on bronchi
bronchodilation and decr mucus secretion -> premedication
atropine therapeutic indications
- premedication before surgery
- eye treatment
- bronchodilation
- antidote
- antidiarrhoeals
- antispasmodics
- treatment of parkinsons in humans
atropine use as premedication before surgery, why is it dangerous before alpha2 agonist administration
it antagonises bradycardia, but does not affect blood vessels
atropine use as premedication before surgery features
- decr saliva production
- decr bronchial secretion, dilating bronchi
- earlier inhalational anaesthetics - new compounds
atropine use for short acting eye treatment
antagonists for diagnostic purposes eg homatropine, tropicamide
atropine use for long acting eye treatment
antagonists for prevention of synechiae eg atropine
atropine use for bronchodilation
-horse RAO =COPD and human/feline asthma -> ipratropium
atropine use as antidote
- organophosphate toxicosis - AChE irreversible inhibitors
- endogenous ACh toxicosis - muscarinic, nicotinic signs alleviated
atropine use as antidiarrhoeal
- relatively obsolete
- not only the peristalsis but also segmental contractions inhibited
- benzethimide - decr secretion and motility, used in ruminants
atropine used as antispasmodic
-decr smooth muscle function - antispasmodic effect on intestine - very effective in horse colic
atropine toxicity
- small therapeutic index
- rabbit relatively resistant - liver atropinase
atropine toxicity symptoms
dry mouth, tachycardia, mydriasis, constipation, convulsions, coma, death
atropine active substances
- atropine
- glycopyrrolate
- homatropine
- tropicamide
- ipratropium
- benzethimid
- butyl-scopalamine
glycopyrrolate features
- not in hungary, very low BBB penetration
- premedication
homatropine use
diagnostic eye examination
tropicamide use
diagnostic eye examination
ipratropium features
- safe, very low BBB penetration
- COPD, asthma
benzethmid use
antidiarrhoeal
butyl-scopolamine use
antispasmodic
active substances for diagnostic eye examination
- homatropine
- tropicamide
