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PHARMACOLOGY OF ANS
part 1
General Pharmacology
M212
Dr. Laila M. Matalqah
Ph.D. Pharmacology
PNS
1. Afferent neuron
the neurons of which bring information from the
periphery to the CNS.
 Afferent neurons provide sensory input to modulate
the function of the efferent division through reflex arcs.

2. Efferent neurons
 carries nerve impulses from the CNS to the
effector organs by way of two types of efferent
neurons (the preganglionic neuron and the
postganglionic neuron
Efferent neurons divisions:
A. Somatic Nervous System:
Carries nerve impulse to skeletal muscle (voluntary control)
 No ganglia
 A single myelinated motor neuron
 Faster response

B. Autonomic Nervous System
Glands, Smooth
Muscle & Cardiac
I.
Parasympathetic Nervous System
Muscle
II. Sympathetic Nervous System
(Involuntary
III. Enteric Nervous system: GIT, pancreas, andcontrol)
gallbladder,
ANS: 1. Sympathetic NS
 Its function: adjusting in response to stressful situations, such as
trauma, fear, hypoglycemia, cold, and exercise
1.
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2.
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Effects of stimulation of the sympathetic division:
Increase heart rate and blood pressure,
To mobilize energy stores of the body,
Increase blood flow to skeletal muscles and the heart while diverting flow from
the skin and internal organs.
Dilation of the pupils and the bronchioles
Decrease GI motility
Fight or flight response
The changes experienced by the body during emergencies have been referred to
as the “fight or flight”
ANS: 2. Parasympathetic NS
 is involved with maintaining homeostasis within the body.
 it maintains essential bodily functions, such as digestive processes
and elimination of wastes
 “rest and digest” situations.
 Note:
Dual innervation: Most organs in the body are innervated by both
divisions of the ANS. PSNS acts opposite to SNS
ANS: 3. Enteric NS
 collection of nerve fibers that innervate the gastrointestinal
(GI) tract, pancreas, and gallbladder,
 This system functions independently of the CNS and controls
the motility, exocrine and endocrine secretions, and
microcirculation of the GI tract.
 It is modulated by both the sympathetic and parasympathetic
nervous systems.
Reflex arcs
CHEMICAL SIGNALING BETWEEN CELLS
 Hormones - chemicals released into the bloodstream
 physiological effects on tissues - specific hormone
receptors.
 Local mediators - Most cells in the body secrete
chemicals that act locally, and they don’t enter blood.
E.g, histamine and prostaglandins –
 Neurotransmitters: A specific chemical signals,
released from the nerve terminals.
Neurotransmitters
1.
2.
3.
4.
5.
6.
Norepinephrine and epinephrine - ANS
Acetylcholine - ANS
Dopamine - CNS
Serotonin - CNS
Histamine - CNS
γ-aminobutyric acid (GABA)- CNS
 Co-transmitters, such as adenosine, often accompany
neurotransmitter on nerve stimulation and modulate the
transmission process.
Neurotransmitters of ANS
1.
Acetylcholine (ACh) (cholinergic )
mediates the transmission of nerve impulses across:
 autonomic ganglia in both sympathetic and parasympathetic NS.
 at adrenal medulla.
 Transmission from the postganglionic nerves to the effector organs in
parasympathetic system,
 transmission at the neuromuscular junction
 A few sympathetic fibers, such as those involved in sweating, are
cholinergic
2.
Norepinephrine (NE) and epinephrine (E)
(adrenergic)
 Transmission from the postganglionic nerves to the effector organs in
sympathetic system
Neurotransmission in cholinergic neurons involves six steps:
Cholinergic receptors (CHOLINOCEPTORS)
A. Muscarinic receptors
 G protein–coupled receptors.
 Recognize muscarine, ACh, and weak affinity to nicotine NT.
 five subclasses of muscarinic receptors:
M1, M2, M3, M4, and M5.
 Found on the effector organs of parasympathetic such as the
gastric (M1) , heart and smooth muscle (M2), bladder and
exocrine glands and smooth muscle (M3)
 When M receptor activated – G-protein – IP3 and DAG intracelluar Ca2+ - cause hyperpolarization, secretion, or
contraction
Cholinergic receptors (CHOLINOCEPTORS)
Cholinergic receptors (CHOLINOCEPTORS)
B. Nicotinic receptors
 ligand-gated ion channel
 Recognize nicotine, ACh, and weak affinity to muscarine NT.
 Two types : Nm and Nn
 Located in the CNS, adrenal medulla, autonomic
ganglia (called Nn), and the neuromuscular junction (NMJ)
called Nm
A. Cholinergic agonists
(parasympathomimetics)
 ACh has both muscarinic and nicotinic activity. Its actions
include:
 Decrease in heart rate and cardiac output
 Decrease in blood pressure (VASODILATION)? HOW?
 Increases salivary secretion and intestinal secretions and motility.
 increases the tone of the detrusor urinae muscle, causing
expulsion of urine.
 constriction of the pupillae sphincter muscle, causing miosis
(marked constriction of the pupil).
1- Direct-acting Agonist Drugs
 Bethanechol: used for urinary retention
 Carbachol: as a miotic agent to treat glaucoma (decrease
the IOP)
 Pilocarpine: to treat glaucoma and lower IOP of both narrow-
angle (or closed-angle) and wide-angle (also called openangle) glaucoma.
2. Indirect-acting Cholinergic Agonists:
Acetylcholinesterase Inhibitors (Reversible)
 Drugs inhibit AChE the enzyme that cleaves ACh to acetate
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and choline and terminate ACh action this results in the
accumulation of ACh in the synaptic space–so prolong ACh
action
Examples:
Physostigmine: used to stimulate the bladder and GI tract.
Neostigmine, ambenonium and Pyridostigmine: used
to treat myasthenia gravis
Rivastigmine: to delay the progression of Alzheimer disease
3. Indirect-acting cholinergic agonists:
anticholinesterases (IRREVERSIBLE)
 Echothiophate: for the chronic treatment of open-angle
glaucoma.
 Long duration of action (1 week)
Reactivation of acetylcholinesterase (Antidote)
 Pralidoxime (PAM) can reactivate inhibited AChE.
 Look at page 57 , fig 4.11
Action of anticholinergic
mydriasis (dilation of the
pupil)
2. antispasmodic (reduce
motility of the GI tract)
3. Reduce Hypermotility
states of the urinary
bladder.
4. blocks the salivary glands
secretion (xerostomia).
1.
I. Antimuscarinic Agents
 1. Atropine:
 used as an antispasmodic to reduce activity of the GI tract
 used to reduce hypermotility states of the urinary bladder.
 Used as antidote for cholinergic agonist
 Antisecretory before surgary.
 Contraindicated on narrow angle glucoma
I. Antimuscarinic Agents
 2. Scopalamine
 used for motion sickness
 3. Ipratropium
 as bronchodilators for maintenance treatment of chronic
obstructive pulmonary disease (COPD)
 4. Benztropine
 treatment of Parkinson disease
II. Neuromuscular-blocking drugs nicotinic
receptors antagonist
1.
A. Nondepolarizing blockers
 Tubocurarine is the prototype agent in this class
 interact with the nicotinic receptors to prevent the binding of Ach
--- inhibit muscular contraction
 Therapeutic uses:
 as adjuvant drugs in anesthesia during surgery to relax skeletal
muscle and to facilitate intubation
2.
Depolarizing agents
 Succinylcholine
 rapid onset and short duration of action, useful when rapid
endotracheal intubation is required