1. Introduction to Autonomic nervous system

2. Neurotransmitter
Chemical substance released from nerve ending, carries impulses across synapses
Combines and stimulates receptors
Main neurotransmitters in ANS are:
Acetylcholine
Noradrenaline, dopamine
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3. Autonomic drugs
Autonomic drugs: mimic or block actions of neurotransmitters
Modify functions of the ANS by stimulation or blockade
Have useful effects
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4. The nervous system CNS: Peripheral NS: Brain Spinal cord
Somatic nerves
Autonomic nervous system (ANS)
Parasympathetic system
Sympathetic system
Enteric nervous system
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7. Autonomic nervous system
Autonomous
Not under conscious control
Controls visceral involuntary functions:
Heart, smooth muscle
Digestion
Exocrine gland functions
Bladder and bowel action
Necessary to maintain life
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8. The ANS Consists of: Sympathetic system (Thoraco-lumbar)
Parasympathetic system (Cranio-sacral)
Enteric nervous system
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9. Anatomy of ANS ANS consists of: Medullary centers
Pregangiolinic fibers
Ganglia
Postganglionic fibers
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12. Parasympathetic system
Preganglionic fibers leave with cranial nerves (3rd oculomotor, 7th facial, 10th vagus nerves) & 3rd – 4th sacral spinal nerves
Ganglia in wall of end organs
From ganglia post-ganglionic fibers run to innervated tissues
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13. Sympathetic system
Preganglionic fibers leave CNS through thoracic and lumbar spinal nerves
Ganglia in the paravertebral chains
From ganglia, post-ganglionic fibers run to innervated tissues
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14. Functions of ANS Regulates involuntary visceral functions:
Heart, SM, digestion, exocrine glands
Sympathetic stimulation:
Stress (physical or emotional), trauma, hypoglycaemia
Lead to fight or flight response:
Increase heart rate, ABP, Blood flow
PS opposes sympathetic function
PS regulates digestion, bladder, bowel function
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15. Functional divisions within the nervous system

20. Enteric Nervous System (ENS)
Collections of neurons in wall of the GIT
3rd division of the ANS
Includes:
Myenteric Auerbach plexus
Submucosal Meissner plexus
Regulates motor & secretory functions of GIT
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21. ENS ENS contains: Cholinergic fibers Adrenergic fibers
Nonadrenergic noncholinergic (NANC) neurons
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22. NANC neurons
Motor & sensory neurons in autonomic target organs (gut, bronchi & bladder)
Neurotransmitters:
Neuropeptides
Substance P
VIP (vasoactive intestinal Plypeptide)
Capsaicin (of chilli peppers) releases neurotransmitters from these neurons
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23. Neurotransmitters of the ANS
Acetylcholine: on cholinergic receptors
Noradrenaline: on adrenergic receptors
Dopamine: on dopaminergic receptors
Other neurotransmitters as:
Neuropeptides
Substance P
VIP
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24. Cholinergic Transmission
Acetylcholine is the neurotransmitter
Acts on cholinoceptors present in:
Autonomic ganglia (sympathetic & parasympathetic)
Postsynaptic fibers of parasympathetic system
Adrenal medulla
NMJ endplates
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25. Pathway of Acetylcholine:
Synthesis:
Choline is transported actively into cholinergic nerve terminals CAT
Acetyl-Co A + choline Ach
Choline acetyltransferase
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28. Pathway of Acetylcholine
Storage:
Ach is transported from cytoplasm into storage vesicles
Protected from degradation
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29. Pathway of Acetylcholine
Release:
Action potential:
Depolarization of nerve terminal
Influx of calcium ions into nerve terminal
Increase intra-neuronal calcium
Fusion of storage vesicles with membrane
Expulsion & release of Ach (exocytosis)
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30. Pathway of Ach in the body
Binding:
Ach binds to & activates cholinoceptors
On post-synaptic & pre-synaptic membranes
Leading to various actions
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31. Pathway of Acetylcholine
Degradation
Ach esterase
Ach choline + acetate
Very rapid
Cholinesterase: in cholinergic synapses & RBC:
Specific for Ach
Pseudocholinesterase in plasma & liver:
Not specific for Ach
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32. Pathway of Acetylcholine
Recycling:
Recycling of choline back into neurons occurs to synthesis new Ach.
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33. Inhibitors of Ach Pathway
Inhibitors of release: Botulinum toxins:
Botulism food poisoning Respiratory paralysis.
Inhibitors of binding of ACh:
Anti-cholinergic drugs.
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34. Cholinoceptors Muscarinic receptors. Nicotinic receptors. 11/17/201834

36. Muscarinic receptors:
M1 CNS Excitatory
M1 Parietal cells Gastric secretion
M Myocardium Rate, contractility, CO
M2 CNS Inhibitory
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37. Cholinoceptors M3 Vascular SM Relaxation
M3 Endothelium Nitric oxide (EDRF)
M3 Circular M of iris Miosis
M3 Exocrine & GIT Increase secretions
M3 GIT & Bladder wall Contraction
M3 GIT, Bladder sphincters Relaxation
M3 Bronchi Bronchoconstriction
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38. Other muscarinic receptors
In corpora cavernosa of penis
Leading to erection through:
Release of nitric oxide causing vasodilatation
M4 & M5 in CNS (not well defined)
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39. Nicotinic receptors Nicotinic NN Autonomic ganglia (Stimulation)
Nicotinic NN Adrenal medulla (Adrenaline, NA release)
Nicotinic NM NMJ endplates
(Muscle contraction)
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40. Adrenergic Drugs Neurotransmitters in adrenergic neurons are:
NA & dopamine
Sympathomimetics:
Mimic actions of sympathetic system
Derivatives of phenylethylamine
Chemical modification results in various agents
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42. Pathway of catecholamines in the body
Binding:
Released NA binds with adrenoceptors:
post-synaptically & pre-synaptic
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43. Termination of actions of NA
Reuptake 1 into nerve terminals (Main)
Reuptake 2 into post-synaptic membrane
Diffusion of NA into circulation
Enzymatic transformation by:
MAO & COMT
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45. Enzymatic transformation
Monoamine oxidase (MAO):
In mitochondria of nerve terminals, intestinal mucosa & liver
Catechol-O-methyl transferase (COMT):
In cytoplasm of liver, lung, brain
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46. Locations & Functions of adrenoceptors in the body
Alpha-adrenoceptors (-Receptors):
Two main subtypes:
1: post-synaptic
2:
Pre-synaptic (Nerve ending)
Post-synaptic in certain sites
In platelets
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47. 1-Adrenoceptors Vascular SM Vsoconstriction
Radial M. of iris Mydriasis
Bladder sphincter Contraction
Intestine sphincter Contraction
Male sex organs Ejaculation
Inhibits K entry into cells Hyperkalemia
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48. IRIS
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49. 2-adrenoceptors Presynaptic Control NA release
- ve feedback inhibition
CNS Inhibitory
Platelets Enhance aggregation
Islet cells pancreas Inhibit insulin secretion
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50. Beta-adrenoceptors (-receptors)
3 subtypes of -adrenoceptors:
1 Heart:
Increase rate, contractility
Increase automaticity & conductivity
1 Kidneys:
Increase renin
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51. 2-adrenoceptors Bronchi Bronchodilatation Bladder wall Relaxation
Intestine wall Relaxation
Skeletal M. arterioles Vasodilatation
Glycogenolysis Increase blood glucose
Gluconeogenesis Increase blood glucose
Uterus Relaxation
Skeletal muscles Tremor
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52.  -receptors 2: Mast cells Inhibits autacoid release
K entry into cells Hypokalemia
3:
Post-synaptic in lipocytes Lipolysis
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