Autonomic Nervous System Flashcards
Parasympathetic division
- Cranial nerves 3, 7, 9, 10
- Sacral nerves S2 - S4
- Long preganglionic and short postganglionic fibers
Sympathetic division
- Thoracic nerves T1 - T12
- Lumbar nerves L1 - L3
- Short preganglionic and long postganglionic fibers
- Adrenal medulla: modified sympathetic ganglion; receives preganglionic nerve and releases epinephrine (Epi; about 80%) and norepinephrine
Choline acetyltransferase
- Syntesizes acetylcholine in the cytoplasm from acetyl-CoA and choline
Vesicle-assoc. transporter (VAT)
- Transports acetylcholine into vesicles; driven by proton efflux
Muscarinic M2 cholinoreceptors locations
- Myocardium
- Smooth muscle
- Some presynaptic sites; CNS neurons
Muscarinic M2 cholinoreceptors results of ligand binding
- Opening of potassium channels
- Inhibition of adenylyl cyclase; reduces contractility and electrical conduction
- Mediates negative impacts on heart function, such as reduce heart rate, atrial contractility and conduction
Muscarinic M3 cholinoreceptors locations
- Exocrine glands
- Vessels (endothelium)
- Smooth muscle
- CNS neurons
Muscarinic M3 cholinoreceptors result of ligand binding
- Like M1 receptor-ligand binding, cause muscle contraction and gland secretion
- Vessel dilation due to EDRF
- Mediates smooth muscle contraction, such as bronchial constriction, increase exocrine gland secretion
- Mediates vasodilation by stimulating vascular endothelial nitric oxide production
Muscarinic M5 cholinoreceptors locations
- Vascular endothelium, especially cerebral vessels
- CNS neurons
- Mediates vasodilation by stimulating vascular endothelial nitric oxide production
Muscarinic M5 cholinoreceptors result of ligand binding
- Like M1 receptor-ligand binding, vessel dilation due to EDRF
Nicotinic Nn cholinoreceptors locations
- Postganglionic neurons, some presynaptic cholinergic terminals
Nicotinic Nn cholinoreceptors result of ligand binding
- Opening of Na+, K+ channels, depolarization
Metyrosine (alpha-methyltyrosine)
- Inhibits the rate limiting step (conversion of tyrosine to dopa) in norepinephrine synthesis
Inactivation of NE
- Neuronal uptake (NE transporter; about 50-80% NE) and simple diffusion: major pathway
- Metabolism by monamine oxidase (MAO) and catechol-o-methyl transferase (COMT): minor pathway
- MAO and COMT mainly metabolize the circulating catecholamines (NE and Epinephrine)
*determination of the 24-h urine excretion of their metabolites (i.e., metanephrine, normetanephrine, 3-methoxy-4-hydroxymandelic acid [VMA]) provides a measure of the total body production of catecholamines and for diagnosis of pheochromocytoma
Alpha1 adrenorectpros locations
- Smooth muscle
Alpha1 adrenoreceptors result of ligand binding
- Formation of IP3 and DAG, increased intracellular calcium
Alpha2 adrenoreceptors locations
- Presynaptic adrenergic nerve terminals
Alpha2 adrenoreceptors locations
- Inhibition of adenylyl cyclase, decreased cAMP
Beta1 adrenoreceptors locations
- Heart
- Juxtaglomerular apparatus of renal tubules
Beta2 adrenoreptros locations
- Heart
- Blood vessels (skeletal muscle)
- 9
- Beta3 adrenoreptors locations
- Lipocytes
Adrenoreptors summary slide
Botulinum toxin autonomic transmission effects
- Prevents transmitter release of cholinergic vesicles
- Tyramine, amphetamine autonomic transmission effects
- Promote transmitter release at adrenergic nerve terminals
Bretylium, Guanethidine autonomic transmission effects
- Block transmitter release at adrenergic nerve terminals
Hemicholinium autonomic transmission effects
- Blocks uptake of choline and slows synthesis at cholinergic nerve terminals: membrane
alpha-Methyltyrosine (metyrosine) autonomic transmission effects
- Blocks synthesis at adrenergic nerve terminals and adrenal medulla: cytoplasm
Vesamicol autonomic transmission effects
- Prevents transmitter storage; depletes vesicles at cholinergic terminals
Reserpine autonomic transmission effects
- Prevents storage; depletes vesicles at adrenergic terminals
Cocaine, tricyclic autonomic transmission effects
- Inhibit uptake; increase transmitter effect at adrenergic nerve
Neostigmine autonomic transmission effects
- Inhibits enzyme; prolongs and intensifies transmitter action at cholinergic synapses (acetylcholinesterase)
Tranylcypromine autonomic transmission effects
- Inhibits enzyme; increases stored transmitter pool at adrenergic nerve terminals (monamine oxidase)
Sympathetic and parasympathetic receptors and their activity on: EYE
Sympathetic
- Iris radial muscle
*receptor: alpha1
*action: constricts
- Ciliary muscle
*receptor: beta
*action: relaxes
Parasympathetic
- Iris circular muscle
*receptor: M3
*action: contracts
- Ciliary muscle
*receptor: M3
*action: contracts
Sympathetic and parasympathetic receptors and their activity on: HEART
Sympathetic
- Sinoatrial node
*receptor: beta1, beta2
*action: accelerates
- Ectopic pacemakers
*same
- Contractility
*receptor: same
*action: increases
Parasympathetic
- Sinoatrial node
*receptor: M2
*action: decelerates
- Contractility
*receptor: M2
*action: decreases
Sympathetic and parasympathetic receptors and their activity on: BLOOD VESSELS
Sympathetic
- Skin, splanchnic vessels
*receptor: alpha
*action: contracts
- Skeletal muscle vessels
*receptor: beta2
*action: relaxes
