Autonomic Nervous System (Cholinergic) Flashcards
What are the cholinergic receptors?
Muscarinic (M1-M5) -Nicotinic (Nn or Nm)
Think acetylcholine binding to these receptors, can be either sympathetic or parasympathetic. But parasympathetic is the postganglionic receptor at the target site so it will have more of a response.
What do heteroreceptor on the presynaptic neuron do?
Hetero = different
Heteroreceptors respond to neurotransmitters, neuromodulators, or neurohormones released from adjacent neurons or cells; they are opposite to autoreceptors, which are sensitive only to neurotransmitters or hormones released by the cell in whose wall they areembedded.
What are the function of autoreceptors?
An autoreceptor is a type of receptor located in the membranes of presynaptic nerve cells. It serves as part of a negative feedback loop in signal transduction. It is only sensitive to the neurotransmitters or hormones released by the neuron on which the autoreceptor sits.
Blood vessels are mainly controlled by what receptors?
Sympathetic control
a1, a2 - Constriction
B2 - Dilation
Location: systemic veins, smooth muscles, arterioles in: skin, splanchnic nerves, skeletal muscle
The eye is mainly controlled by what receptors and systems?
Sympathetic control
a1 - Contraction (mydriasis)
B2 - Relaxation to far vision
Parasympathetic control
M3 - Contraction (miosis)/near vision
M - Tear secretion
Receptors in the genitourinary smooth muscle?
Sympathetic control
B2/B3 - Relaxation of bladder wall
a1 - Contraction trigone and sphincter/ uterus, pregnant
Parasympathetic control
M3 - Contraction of bladder/Relaxation of sphincter
M - Erection of penis
Receptors in the heart?
Sympathetic control
B1 - Increase heart rate at SA node/Increase conduction at AV node/purkinje
B1/B2 - Increase in contractility in atria and ventricles
Parasympathetic control
M2 - Decreae heart rate in SA node/Decrease conduction at AV node/purkinje/Decrease atrial contractility
Receptors in the stomach and intestines?
Sympathetic control
a2/B2 - Decrease motility and tone
a1 - Contraction of sphincter
Parasympathetic control
M3 - Increase motility/tone, relax sphincter, stimulate secretion
Receptors in lungs?
Sympathetic control
B2 - Relaxation
a1 - Decreased secretion
B2 - Increased secretion
Parasympathetic control
M3 - Contraction/stimulation
Receptors in the skin?
Sympathetic control
a1 - Contraction pilomotor smooth muscle
M - Increase sweat secretion (Ach)
Receptors in the liver?
Sympathetic control
a1/B2 - glycogenolysis and gluconeogenesis
What are the effects of muscarinic agonists?
- effects may be blocked by a muscarinic receptor antagonist
- Alkaloids
- Mimic Ach at muscarinic/nicotinic receptors to generate parasympathetic responses
Direct acting cholinergic/muscarinic agonists?
Acetylcholine (cholinergic) -> Very susceptible to AchE and nictotinic receptors
Methacholine (muscarinic) -> less susceptible to AchE and more cardiac effects than Ach. Does not affect skeletal muscle. Used for diagnosis of asthma.
Bethanechol (muscarinic) -> not susceptible to AchE, more GI effects (urination) and eye effects. Does not affect skeletal muscle. Stimulates urination.
Nicotinic receptor agonists?
Nicotine -> tobacco use or smoking cesation/dose related effect
Succinylcholine -> Depolarizing muscular blocker that causes depolarization and eventually blocks the nicotinic receptor becoming an antagonist
Indirect acting cholinergic agonists?
Endrophonium (Reversible) -> has alcohol group, and is short lived (2-10 min), very fast acting and can be used to reverse MR quickly
Neostigmine/Prostigmine (Reversible) -> carbamic acid ester, longer duration of action (30min to 6hrs) used to reverse MR
Physostigmine (Reversible) -> tertiary NH, can cross BBbarrier so is used as atropine overdose reversal where CNS was affected
