🌟 AUTONOMIC NERVOUS SYSTEM (ANS) – EXAM NOTES (RANG & DALE +
TRIPATHI)
✅ 1. INTRODUCTION TO ANS
The ANS controls involuntary functions: cardiac output,
blood pressure, digestion, body temperature, glandular secretions.
Divisions:
- Sympathetic Nervous
System (SNS) – “Fight, Flight, Fear”
- Parasympathetic Nervous
System (PNS) – “Rest, Relax, Digest”
- Enteric Nervous System
(ENS) – intrinsic GI system
Neurotransmitters:
- ACh
– all preganglionic neurons (SNS & PNS), postganglionic PNS, sweat
glands (SNS)
- NA (Norepinephrine)
– most postganglionic SNS
- Epinephrine
– released by adrenal medulla
✅ 2. ANATOMICAL ORGANIZATION (VERY IMP)
|
Feature |
Sympathetic |
Parasympathetic |
|
Origin |
Thoracolumbar (T1–L5) |
Craniosacral (III, VII, IX, X;
S2–S4) |
|
Ganglion |
Near spinal cord |
Near or inside target organ |
|
Fiber length |
Short preganglionic, long
postganglionic |
Long preganglionic, short
postganglionic |
|
NT at ganglion |
ACh on Nn |
ACh on Nn |
|
NT at effector |
Mostly NA |
ACh
on M receptors |
✅ 3. RECEPTORS OF ANS (VERY HIGH YIELD)
Cholinergic receptors
Muscarinic (GPCR)
- M1
– CNS, gastric parietal cells → ↑cognition, ↑HCl
- M2
– Heart → ↓HR, ↓AV conduction
- M3
– Smooth muscle & glands → bronchoconstriction, ↑secretions,
↑motility, miosis
- M4/M5
– CNS (less important)
Nicotinic (Ligand-gated ion channels)
- Nm
– skeletal muscle (NMJ)
- Nn
– autonomic ganglia, adrenal medulla
Adrenergic receptors (SNS)
Alpha receptors
- α1
(Gq): Vasoconstriction, ↑BP, mydriasis, urinary retention
- α2
(Gi): ↓NE release (autoreceptor), ↓insulin
Beta receptors
- β1
(Gs): ↑HR, ↑Contractility, ↑Renin
- β2
(Gs): Bronchodilation, vasodilation, uterine relaxation, ↑glucose
- β3
(Gs): Lipolysis, bladder relaxation
📌 Mnemonics
M1 – Mind,
M2 – Muscle of heart,
M3 – Movement of smooth muscle, secretions
β1 – 1 heart,
β2 – 2 lungs,
α1 – constricts 1 vessel
✅ 4. ANS NEUROTRANSMISSION (Rang & Dale Core Concept)
Steps:
1.
Synthesis
- ACh
from choline + acetyl-CoA
- NA
from tyrosine → DOPA → dopamine → NA
2.
Storage in vesicles
3.
Release (Ca²⁺ dependent)
4.
Receptor activation
5.
Inactivation
- ACh
→ broken by AChE
- NA
→ reuptake (NET), MAO, COMT
Drugs acting on each step
|
Step |
Drug |
|
Choline uptake block |
Hemicholinium |
|
Vesicle block |
Vesamicol |
|
Release block |
Botulinum
toxin |
|
NA release ↑ |
Amphetamine,
Tyramine, Ephedrine |
|
NA reuptake block |
Cocaine,
TCAs |
|
MAO inhibition |
Selegiline,
Phenelzine |
✅ 5. EFFECTS OF ANS ON ORGANS (Tripathi Table)
|
Organ |
Sympathetic |
Parasympathetic |
|
Eye |
Mydriasis (α1) |
Miosis (M3) |
|
Heart |
↑HR, ↑Contractility (β1) |
↓HR (M2) |
|
Lungs |
Bronchodilation (β2) |
Bronchoconstriction |
|
GIT |
↓Motility (α2, β2) |
↑Motility, ↑secretions (M3) |
|
Bladder |
Urinary retention (α1, β2) |
Urination (M3) |
|
Blood vessels |
Vasoconstriction (α1),
vasodilation (β2) |
No major effect |
✅ 6. CHOLINERGIC DRUGS (Summary)
Direct-acting agonists
- ACh, Bethanechol
(urinary retention), Pilocarpine (glaucoma), Carbachol
Indirect-acting (AChE inhibitors)
- Reversible:
Neostigmine, Physostigmine, Pyridostigmine, Rivastigmine
- Irreversible:
Organophosphates (malathion, parathion)
Uses
- Myasthenia
gravis (pyridostigmine)
- Glaucoma
(pilocarpine)
- Alzheimer’s
(rivastigmine)
Toxicity
- SLUDGE:
Salivation, Lacrimation, Urination, Diarrhea, GI upset, Emesis
- Treatment:
Atropine + Pralidoxime
✅ 7. ANTICHOLINERGICS
Atropine, Ipratropium, Glycopyrrolate, Tropicamide, Dicyclomine
Uses:
- Asthma/COPD
(ipratropium)
- Preanaesthetic
(glycopyrrolate)
- Eye
dilation (tropicamide)
- IBS
(dicyclomine)
- Bradycardia,
organophosphate poisoning (atropine)
✅ 8. ADRENERGIC DRUGS
Sympathomimetics
- α1 agonists:
Phenylephrine (nasal decongestant)
- β2 agonists:
Salbutamol, Terbutaline (asthma)
- β1 agonists:
Dobutamine (CHF)
- Mixed:
Epinephrine, Noradrenaline
Adrenergic blockers
- α-blockers:
Prazosin (HTN), Tamsulosin (BPH)
- β-blockers:
- Non-selective:
Propranolol
- β1-selective:
Metoprolol, Atenolol
- Mixed:
Carvedilol
🔥 Most Important Exam MCQs (Predictable)
- All preganglionic fibers
release? → ACh
- Bronchodilation mediated
by? → β2
- Drug blocking vesicular
storage of ACh? → Vesamicol
- Organophosphate
poisoning antidote? → Atropine + Pralidoxime
- Sweat gland innervation?
→ Sympathetic but cholinergic
- Drug inhibiting NA
reuptake? → Cocaine
- Mydriasis without
cycloplegia? → α1 agonists (phenylephrine)
📌 FLOWCHART (SUPER QUICK REVISION)
ANS│├── Sympathetic (NA)│ ├── α1 = vessels constrict│ ├── α2 = ↓NE release│ ├── β1 = ↑HR, ↑renin│ ├── β2 = bronchodilation, vasodilation│ └── β3 = lipolysis│└── Parasympathetic (ACh) ├── M1 = CNS + gastric acid ├── M2 = heart ↓HR └── M3 = smooth muscle + glands + eye miosis
✅ 1. DIRECT-ACTING CHOLINERGIC AGONISTS – QUICK TABLE
|
Drug |
Type |
Key Features |
Indications |
Memory Trick |
|
Choline ester |
Non-selective, rapid hydrolysis |
All Channels Open (non-selective) |
||
|
Choline ester |
β-methyl → M-selective |
Metha – M for Muscarinic |
||
|
Carbachol |
Choline ester |
Resistant to AChE |
Carb = hard (hard to breakdown) |
|
|
Choline ester |
M-selective + resistant |
Urinary retention, atonic bladder |
Betha-nech-oL = Bladder + cOLon |
|
|
Alkaloid |
Tertiary amine |
Glaucoma, xerostomia |
Pilo – Pillow → saliva drools on pillow |
✅ 2. INDIRECT-ACTING CHOLINERGIC DRUGS – REVERSIBLE
|
Drug |
Type |
CNS? |
Indications |
Mnemonic |
|
Carbamate |
No (quaternary) |
Neo = No CNS |
||
|
Carbamate |
No |
MG (long acting) |
Pyrido – Period long |
|
|
Carbamate |
Yes (tertiary) |
Physo = Physically crosses BBB |
||
|
Alcohol |
No |
Tensilon test |
E-dro = short like "drop" |
✅ 3. IRREVERSIBLE AChE INHIBITORS
|
Drug |
Key Feature |
Indication |
Mnemonic |
|
Echothiophate |
Stable AChE complex |
Glaucoma |
Echo sticks forever |
|
Parathion / Malathion |
Insecticides |
Poisoning |
Para – Pesticide |
✅ 4. CHOLINERGIC ADRs – SUPER MNEMONICS
🔹 Muscarinic Excess = SLUDGE-BBB
- Salivation
- Lacrimation
- Urination
- Diarrhea
- GI cramps
- Emesis
- Bronchoconstriction
- Bradicardia
- Blurred vision
**Mnemonic:
👉 “SLUDGE + 3B”**
✅ 5. SAR OF CHOLINERGIC DRUGS – TABLE
|
SAR Point |
Effect |
Easy Mnemonic |
|
Quat. ammonium |
Required for activity |
N⁺ = Needs positive |
|
Ester chain = 2 carbons |
Optimal activity |
ACh = Ace = perfect 2 |
|
β-methyl group |
↑ Muscarinic selectivity |
β = B = Bias to M receptors |
|
Carbamate |
Resistant to AChE |
Carb = cannot be cut |
|
Tertiary amine |
CNS entry |
3° = 3 letters → BBB |
|
Quaternary amine |
No CNS entry |
4° = 4 walls block BBB |
✅ 6. HETEROCYCLIC CORE – REVISION TABLE
|
Drug |
Heterocyclic Ring |
Memory Aid |
|
Pilocarpine |
Imidazole |
Pilo = Puzzle = Imidazole |
|
Physostigmine |
Indole |
Physo → "In" CNS → Indole |
|
Pyridostigmine |
Pyridine |
Pyrido = Pyridine |
|
Galantamine |
Tetracyclic |
Galant = grand (big rings) |
|
Donepezil |
Indanone + Piperidine |
Done = Dual rings |
✅ 7. INDICATIONS – ULTRA FAST MNEMONIC
“B P N P D – Bladder, Pupil, NMJ, Poisoning, Dementia”
|
Category |
Drugs |
Memory |
|
Bladder |
Bethanechol |
B for Bladder |
|
Pupil (glaucoma) |
Pilocarpine, Carbachol |
P for Pupil |
|
NMJ (Myasthenia) |
Neo, Pyri |
N for NMJ |
|
Poisoning |
Physostigmine |
P for Poison |
|
Dementia |
Donepezil, Rivastigmine |
D for Dementia |
⚡ QUICK MASTER MNEMONICS (EXAM HITS)
1️⃣ “BeCaMe ACh” → Direct agonists
- Bethanechol
- Carbachol
- Methacholine
- ACh
2️⃣ “NEO-PHY-E” → MG drugs
- Neostigmine
- Physostigmine
- Edrophonium (diagnosis)
3️⃣ For organophosphate poisoning treatment
👉 “A.P.” = Atropine + Pralidoxime
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