4. AUTONOMIC NERVOUS SYSTEM
The autonomic nervous system (ANS) is a
division of the peripheral nervous system that
influences the function of internal organs.
It is a control system that acts largely unconsciously
and regulates bodily functions such as the heart
rate, digestion, respiratory rate, pupillary
response, urination, and sexual arousal.
This system is the primary mechanism in control of
the fight-or-flight response and the freeze-and-
dissociate response.
5. Fig : Schematic diagram comparing some anatomic and
neurotransmitter features of autonomic and somatic motor nerves.
Anatomy of autonomic nervous system
6. Anatomy of autonomic nervous system
The autonomic nervous system is devided into two major portions:
the sympathetic (thoracolumbar) division and the parasympathetic
(craniosacral) division
The sympathetic preganglionic fibers leave the
central nervous system through the thoracic and lumbar spinal nerves.
The parasympathetic preganglionic fibers
leave the central nervous system through the cranial nerves
(especially the third, seventh, ninth, and tenth) and
the third and fourth sacral spinal roots
7.
8. CHOLINERGICS
Parasympathomimetics or cholinomimetics
Stimulate parasympathetic nervous system in same
manner as does acetylcholine
May stimulate cholinergic receptors directly or slow
acetylcholine metabolism at synapses (affect the
enzyme acetylcholinesterase)
11. ORGAN SYSTEM EFFECTS
Eye
Miosis
Enhance drainage of aqueous humor from the
anterior chamber
Cardiovascular system
Bradycardia(This is due to receptor activation)
Decreased inotropic and chronotropic effects
Vasodilation(This is due to M3 receptor
activation)
12. CONT…
Respiratory tract
Bronchoconstriction
Stimulation of bronchial secretions.
GIT
Increase in muscle tone
Increase in peristaltic contractions
Stimulation of gastric secretions
Genitourinary tract
Relax the trigone and sphincter muscle of the bladder,
thus promote voiding.
13. CLINICAL USE OF CHOLINERGIC AGONISTS
1. Treatment of glaucoma :
Carbachol and Pilocarpine are the direct agents chosen.
Physostigmine is an anticholinesterase used.
2. Treatment of atony of GIT:
Bethanechol is the most widely used direct agent and
Neostigmine is the most widely used anticholinesterase
for this purpose.
3. Treatment of xerostomia:
Bethanechol and pilocarpine are used to increase
salivary secretion to treat xerostomia (dry mouth).
14. CLINICAL USE OF CHOLINERGIC AGONISTS
CONT…
1. Myasthenia gravis:
Neostigmine, pyridostigmine and ambenonium are
most widely used. Edrophonium is used as the
diagnostic agent.
2. Alzheimer’s disease:
Anticholinesterase such as tacrine (no longer used
widely), galantamine, rivastigmine, donezepil are
used in alzheimer’s disease.
15. ANTICHOLINERGICS
Anticholinergics are the class of drugs that block
the actions of acetylcholine in the PSNS.
Anticholinergics are competitive antagonists that
compete with acetylcholine for binding at the
muscarinic receptors of the PSNS, inhibiting nerve
transmission.
This effect occurs at the neuroeffector junctions of
smooth muscle, cardiac muscle, and exocrine
glands.
16. Muscarinic Receptor Subtypes
M1 M2 M3 M4 M5
Location • CNS
• Stomach
• Heart
• CNS
• Airway
Smooth
Muscle
• CNS
• Salivary
glands
• Airway
smooth
muscle
• Vascular
endothelial
cells
• CNS
• Heart
• CNS
Clinical
Effects
• Hydrogen
Ion Secretion
• Bradycardi
a
• Salivation
• Bronchodilat
ion
• Vasodilation
? ?
Clinically
selective
drugs
available
Yes No No No No
18. ORGAN SYSTEM EFFECTS
Eye
Cyclopegia
Mydriasis
Photophobia (due to mydriasis)
CVS
Bradycardia at lower dose
Tachycardia at higher dose(Blocking of M2 receptor of heart)
Respiratory tract
Broncodilation
Inhibition of bronchial, nasal secretion.
GIT
Decrease muscle tone in the GIT
Decrease peristaltic contraction.
Decrease gastric secretions.
Decrease salivary secretions (dry mouth).
19. CONT…
CNS
Restlessness
Irritability
Hallucination
CNS depression (when dose of atropine is above 2mg)
Paralysis of respiratory muscle, cardiac reflex etc.
Genitourinary tract
Relaxes smooth muscle of the ureters and bladder wall and
slows voiding.
Sweat gland
Suppresses thermoregulatory sweating.
20. CLINICAL USE
CNS disorders:
Parkinson’s disease: Benztropine, benzhexol etc. are used.
Motion sickness: Scopolamine has been used.
Ophthalmic disorders: Usually atropine, tropicamide and
cyclopentolate are used.
Respiratory disorders: Anti-muscarinic agents such as
ipratropium bromide and tiotropium therefore are very effective
bronchodilators.
Gastrointestinal disorders:
Anti-muscarinic agents can be used in the treatment of peptic
ulcer (e.g. pirenzepine, dicyclomine).
They can also be used for diarrhea.
They are used to shut down GIT before surgery.
21. CONT…
Urinary disorders:
Oxybutynin is used to relieve post-operative urinary bladder spasm.
Oxybutynin and some new drugs (Darifenacin, solifenacin) are used
to treat urinary incontinence in geriatric patients.
Cholinergic poisoning: Atropine is used as antidote in the poisoning by
cholinergic agonists .Pralidoxime is also used.
22. ADRENOCEPTOR ACTIVATING DRUGS
Drugs that mimic the action of epinephrine or
norepinephrine are called adrenoceptor activating or
sympathomimetic drugs.
Available Drugs
𝜶 𝟏
Selective
𝜶 𝟐
Selective
β 𝟏
Selective
β 𝟐
selective
Non-selective
Tetrahydrozoline Clonidine Dobutamine Terbutaline Isoprenaline
Naphazoline α-methyldopa Albuterol Epinephrine
26. Clinical Use & Side Effect
adrenoceptor activating drugs
Anaphylactic shock:
In cardiac arrest and bradycardia
During surgery.
In bronchial asthma.
Side Effect:
Arrhythmia
Hypertension
Tremor
Headache
Urinary retension
27. ADRENERGIC BLOCKER
Bind to adrenergic receptors, but inhibit or block
stimulation of the sympathetic nervous system (SNS)
Have the opposite effect of adrenergic agents
Also known as
-adrenergic antagonists or sympatholytics
28.
29. Clinical pharmacology the alpha receptor
blocking drugs
Pheochromocytoma: The major clinical use of
phenoxybenzamine is in the management of
pheochromocytoma. Pheochromocytoma is a tumor of the
adrenal medulla or sympathetic ganglion cells.
Chronic Hypertension;Members of the prazosin family of
α1-selective antagonists are efficacious drugs in the
treatment of mild to moderate systemic hypertension.
Urinary Obstruction:Prazosin, doxazosin, and terazosin
are all efficacious in patients with Benign prostatic
hyperplasia.
30. Clinical pharmacology the beta-
receptor blocking drugs
Hypertension:The β-adrenoceptor–blocking drugs have proved to be
effective and well tolerated in hypertension.
Ischemic Heart Disease:Beta-adrenoceptor blockers reduce the
frequency of anginal episodes and improve exercise tolerance in many
patients with angina.Timolol,propranolol, or metoprolol are used in
patients who have myocardial infarction.
Cardiac Arrhythmias:Beta antagonists are often effective in the treatment
of both supraventricular and ventricular arrhythmias.
Glaucoma:Systemic administration of β-blocking drugs for other
indications was found serendipitously to reduce intraocular pressure in
patients with glaucoma.