Introduction to ANS Flashcards
Enteric Nervous System divisions:
Myenteric plexus (Auerbach’s)
Submucosal plexus (Meissner’s)
Additional functions of enteric neurons?
Mechanoreceptors
Chemoreceptors
Substances released by excitatory enteric neurons?
Ach and Substance P
Serotonin, Nitric Oxide, and Neuropeptide Y
Enkephalins, dopamine, ATP
Substances released by inhibitory enteric neurons?
Dynorphin and VIP
Activity in the ENS is largely modulated by the?
Sympathetic NS
Ratio of pre-ganglionic to post-ganglionic fibers in ENS?
1:1000
Norepi containing ENS neurons ____?
Inhibit intestinal motility
Norepi + Neuropeptide Y containing ENS neurons ____?
Regulate blood flow
Norepi + Somatostatin containing ENS neurons ____?
Control intestinal secretion
PSNS
Craniosacral Longer preganglionic fiber 1:1 or 1:2 ratio Localized/Discrete response Maintains Homeostasis Ach, Nicotinic & Muscarinic receptors
SNS
Thoracolumbar Shorter preganglionic fiber 1:20 ratio Generalized response Emergency situations NE, N & M, a&b receptors
Drugs that block Na channels:
Saxitoxin (red tide toxin)
Tetrodotoxin (puffer fish toxin)
Local anesthetics
Toxin that inhibits neurotransmitter release?
Botulinum toxin
What follows generalized permeability change?
Depolarization followed by excitatory post-synaptic potential
What follows selective (small ion) permeability change?
Hyperpolarization (K efflux) followed by Inhibitory post synaptic potential
Ach is degraded by?
Acetycholinesterase (major)
Plasma/butyryl pseudocholinesterase (non-specific)
NE is degraded by?
catechol O' methyl transferase (COMT) monoamine oxidase (MAO)
COMT is found where?
Liver and muscle
Where is MAO found?
Mitochondria, cytoplasm, nerve terminal, liver, intestine
Major pathway for termination of NE action?
Neuronal uptake (uptake 1)
What is diffusion of transmitter into perisynaptic glia and the muscle?
Extra-neuronal uptake (uptake 2)
Acetyl CoA and choline rx in the cytoplasm is catalyzed by?
ChAT (choline acetyl transferase)
The rate limiting step in Acetylcholine synthesis?
Entry of choline in to the nerve ending
Maximum Ach molecules after nerve firing?
How long do they remain in the nerve terminal?
3 Million
1 ms
Rate limiting step in NE synthesis?
Conversion of tyrosine to DOPA by tyrosine hydroxylase
2 pools of norepinephrine:
Vesicular pool
Cytoplasmic pool
The only local anesthetic that causes vasoconstriction?
Cocaine (prevents reuptake of NE)
Indirectly acting sympathomimetics:
Tyramine and Amphetamine
Cocaine and tri-cyclic antidepressants
Heteroreceptor a2:
Parasympathetic terminal, inhibits Ach
Heteroreceptor M2/M4:
Sympathetic terminal, inhibits NE