Autonomic Pharmacology Flashcards
What can the peripheral nervous system be broken down into?
- Afferent (sensory)
- Efferent (motor)
What can efferent nervous system be broken down into?
- Somatic (conscious)
- Autonomic (unconscious)
What are the two branches of autonomic (ANS) and what are their functions?
SNS - fight or flight
PSNS - rest and digest
What does dominant tone mean?
Either SNS or PSNS dominates in certain organs
What receptors are used in the PSNS?
- Cholinergic
- Muscarinic
What receptors are used in the SNS?
Adrenergic
Where does PSNS originate from?
cranio-sacral
Where does SNS originate from?
thoraco-lumbar
True or false (and why):
Most drugs target ganglia
False. Most drugs target the post ganglionic receptors for selective effect
Both SNS and PNS have (blank) in their preganglionic and postganglionic fibres
ganglion
This NT is released onto the ganglia in both SNS and PSNS:
Ach
What are the receptors at the ganglia
Nicotinic receptors
How Acetylcholine stored and synthesized?
Synthesized from Acetyl CoA and Choline
Stored in synaptic vesicles
What do post-ganglionic neurons of the SNS release?
Norepinephrine (NE)
What does the adrenal medulla release?(include percentages)
20% NE and 80% Epi
What do postganglionic parasympathetic nerves release?
Ach
Key NT synthesized from: (and what they are called as a group)
From tyrosine
Called Catecholamines
Receptor distribution: Cholinergic
Nicotinic
Muscarinic (5 subdivisions)
M1, M3, M5
M2, M4
Receptor distribution: Adrenergic
Alpha: a1, a2
Beta: B1, B2, B3
M1, M3, M5 receptors
PSNS: muscarinic
G-protein coupled (GQ)
Excitation - when agonist binds = increase activity
M2, M4 receptors
PSNS (muscarinic)
G-protein coupled (Gi)
Inhibitory - when bound to receptor = decrease activity
Effect of muscarinic receptors on:
1. Heart
2. lungs
3. sphincters (specifically which ones)
4. walls (specifically what walls)
- heart = M2, decreased rate/contraction (rest)
- lungs = bronchoconstriction
- sphincters = M3, relaxation of GI and bladder sphincters
- walls =M3, contraction of GI tract and bladder walls
PSNS effect on secretion (specific what secretion)?
Increased
salivary, respiratory, tears
Two main paths to stimulate M receptors?
- Direct
- Indirect
What is direct stimulation of M receptor?
Using an agonist
What is indirect stimulation of M receptor?
acetylcholinesterase inhibitors increase the concentration of acetylcholine
Reversible or Irreversible
What are the three types of chemical reaction that can occur when cholinesterase is bound?
acetylation, carbamylation, phosphorylation
What is the result of the following when cholinesterase is bound?
1. acetylation
2. carbamylation
3. phosphorylation
- acetylation = What happens normally in our body, rapidly recover the cholinesterase
- carbamylation = slower recovery but is still reversible
- phosphorylation = irreversibly bound - no recovery
Excessive cholinergic response affect which systems (5)
Secretions
lung
heart
GI mobility
Urinary tract
Excessive cholinergic response specific symptoms:
1. secretions
2. lungs
3. heart
4. GI motility
5. Urinary tract
- secretions = increased drooling, tearing, clogged airways
- lungs = Bronchoconstriction (difficulty breathing)
- heart = Reduced heart rate (decreased endurance)
- GI motility = Increased (nausea, vomiting, diarrhea)
- Urinary tract = contraction of bladder, relaxation of sphincters (urination)
Parasympatholytics (aka):
Block PSNS response
AKA: anticholinergics or antimuscarinics
Atropine
Prototypical anticholinergic
What are uses for atropine? (4)
Intubation
Opthalmology
Asthma
Antidote
How can atropine be used for the following?
1. Intubation
2. Opthalmology
3. Asthma
4. Antidote
- Intubation = Clear airways by drying up secretions
- Opthalmology = Dilate pupils to facilitate eye exams
- Asthma = Dilate bronchioles
- Antidote = Counteract poisoning by cholinesterase inhibitors
Side effects of atropine
Mouth - dry mouth
Heart - tachycardia
Gut - constipation
Bladder - Difficulty urinating
A1 receptor function
constriction of smooth muscle
Locationof A1 receptors
- Sphincters: bladder, GI tract
- Blood vessels: vasoconstriction
How do a1 receptors work?
G protein coupled
A2 receptor function
inhibition of NE release
Location of A2 receptors
presynaptic membrane
How do a2 agonists work?
binding agonist to presynaptic a2 receptors inhibits release of NE
Function of B1 receptor
- Heart stimulation (increased rate, atrioventricular conduction and contractility)
- Kidney (stimulate renin release = increase blood pressure)
What 3 parts in the body are only innervated by the SNS?
liver kidney and uterus
B2 receptor function
relaxation of smooth muscle
Location of B2 receptor
- lungs - bronchodilation
- blood vessels in skeletal muscle - vasodilation
- GI tract, bladder, uterus WALLS- relaxation
How does b2 receptor affect the liver?
beta 2 receptors mediate glucose release through:
1. gluconeogenesis
2. glycogenolysis (breakdown of glycogen to glucose)
How does SNS affect the bladder?
B2 in bladder wall relaxes - no forcing of liquid out
A1 in sphincter contracts - stops fluid from leaving
prevents peeing from occuring
Sympathomimetics
drugs that mimic the stimulation of the SNS
How do sympathomimetics work?
by directly activating adrenergic receptors
by increasing the amount of NT in the synpase
How to increase the amount of NT in synpase?
- increase NT release
- inhibit reuptake of NT
- inhibit metabolism of NT
What is the mechanism to reuptake NT?
Reuptake pumps sit pre synpatically and remove Nt to stop them from binding to receptors
What is the mechanism for metabolism of NT?
MAO (monoamine oxidase) - breaks down catecholamines like NE, serotonin, Dopamine
Sympatholytics
drugs that reduce or block the sympathetic activity
What is an example of a drug that directly blocks adrenergic receptors?
propanolol - a beta blocker/antagonist
What is an example of a drug decreases the amount of NT that is released into synpase?
clonidine - a2 agonist
What two muscles control the eye?
- Iris muscle (circular, radial muscle)
- Ciliary muscle
What receptors control the circular muscle and what happens when it contracts?
M2, M3 receptors
contraction constricts pupil
What receptors control the radial muscle and what happens when it contracts?
A1 receptor
contraction dilates pupil
What does the ciliary muscle control?
- Shape of the lens and focuses image on retina
- Production of aqueous humor (AH)
What is glaucoma caused by?
An increase in intraocular pressure (IOP)
What causes an increase in IOP?
Build up of Aq humour due to decreased drainage/increased production
PSNS treatment for glaucoma
M2 M3 receptor stimulation
contracts ciliary muscle, opens trabecular meshwork and canal of schlemm -> more drainage can occur
SNS treatment for glaucoma
- B2 agonists to reduce Aq humor secretion
- A2 agonists to facilitate drainage/reduce production
What other things in the eye does M receptor stimulation affect?
M receptor stimulation= contraction of ciliary muscle
causes lens to bulge - improves near vision but blurs far vision