Cholinergic System:
Acetylcholine – Neurotransmitter for ganglionic synapse between preganglionic
and postganglionic fibers of both the sympathetic and parasympathetic NS’s.
Neurotransmitter at the junction between the parasympathetic postganglionic fiber
and the effecter cells
Adrenergic system:
Norepinephrine – Neurotransmitter between the sympathetic postganglionic fiber
and the effector cell.

Fibers that release norepinephrine and called adrenergic fibers.

Stimulation of sympathetic and parasympathetic fibers stimulate certain
organs and inhibit others.
Divisions of ANS
A. Parasympathetic
a. Concerned with vegetative functions
i. Less kinetic
ii. Concerned with conservation and restoration of function
b. Cholinergic nervous systems
i. Acetylcholine is chemical mediator
ii. Cholinergic nerves
1. Nerves releasing acetylcholine at their receptor
terminal
c. Acetylcholinesterase
i. After chemical mediator transmits stimulus to receptor it is
then broken down (metabolized) by enzyme
ii. Acetylcholine – acetylcholinesterase
d. Epinephrine and norepinephrine (sympathetic NS)
i. Metabolized in liver or bowel
ii. Amine oxidase
e. Vagus nerve is primary mode of parasympathetic transmission
i. 80%
f. stimulation
i. Slower cardiac rate
ii. Decrease stroke volume
iii. Decrease cardiac output (HR X SV = CO)
iv. Decrease blood pressure
v. Increase peristalsis and digestion
KEYPOINT: adverse effects of vagus nerve is decreased HR, SV, and CO.
g. Dominant nervous system of cardiac muscle
h. Two portions or receptors
i. Muscarinic – involved with organs innervated by 10th cranial
nerve
1. Stimulation lower HR and BP
ii. Nicotinic
1. Motor nerves to skeletal muscles
2. Muscle relaxants act on these receptors
B. Sympathetic
a. Fight or flight syndrome
i. Protect integrity
ii. Maintains safety of organism
b. Prepares body to respond to stress
c. Adrenergic nervous system
i. Nerves whose impulses act through release of catecholamine
ii. Chemical mediators
1. Epinephrine
2. Norepinephrine
3. Produced by medulla of adrenal glands
iii. Stimulation
1. Increase cardiac rate
2. Increase stroke volume
3. Increase cardiac output
4. Aids O2 demands of tissues
C. Response
a. Sympathetic and parasympathetic are antagonist to each other
b. Action maintains a constant tone
D. Medications can act in four ways upon ANS
a. Stimulate sympathetic nervous system
i. Sympathomimetic
b. Inhibit sympathetic nervous system
i. Sympatholytic
c. Stimulate parasympathetic
i. Parasympathomimetic
d. Inhibit parasympathetic
i. Parasympatholytic
E. Receptors sites of sympathetic nervous system
a. Alpha adrenergic receptors
i. Alpha 1 and 2 receptors
ii. Located in vascular smooth muscle and skeletal muscle
iii. Stimulation
1. Contraction of vascular smooth muscle
2. Vasoconstriction
3. Increase SVR
4. Increase BP
5. Little or no bronchoconstriction
Alpha 1 primary neurotransmitter is norepinephrine (Levifed)
6. Alpha 2 inhibits the release of norepinephrine from
adrenal gland
b. Beta adrenergic receptors
i. Beta 1
1. Located in myocardial muscle and electrical cells
2. Increase cardiac rate; increase stroke volume or
contraction
3. Increase automaticity
4. Increase conductivity
5. Increase cardiac output
6. Increase myocardial O2 requirements
7. Main drug = Epinephrine
ii. Beta 2
1. Located bronchial smooth muscle
2. Located skeletal vascular muscle
3. Relaxes bronchial smooth muscle resulting in
bronchodilation
4. Relaxes vascular smooth muscle; decreases PVR
5. Mechanism of bronchodilation
a. Smooth muscle cells of tracheobronchial tree
contain intracellular enzyme C-AMP
b. Increase levels of C-AMP cause chemical reaction
relaxing bronchial musculative
c. Bronchodilation results
d. Decrease levels of C-AMP result
bronchoconstriction
e. Bronchodilators cause increase in C-AMP
i. Increased production – catecholamines –
bronchodilation
ii. Decreased breakdown – methylronthines
– bronchodilation
iii. Cyclic 3,5 AMP bronchodilation mecanism
1. Cathecholimines
(sympathminetrics) stimulate Beta
2 receptors
2. Beta 2 receptors releases
adenylcyclase
3. ATP to C3,5 AMP = bronchodilation
4. Phosphodiesterase breaks down
C3,5 AMP
c. Dopaminergic
i. Located coronary blood vessels
ii. Located in renal and mesenteric blood vessels
iii. Stimulation causes dilation
iv. Dopamine
F. Alpha and beta drug agents
a. Knowledge of whether a sympathetic drug is an alpha or beta agent
one can predict its physiological affects
i. Cardiac effects
ii. Arterial effects
iii. Lung effects
b. Medication examples
i. Isoproterenol
1. Pure beta agent
2. Stimulates hearts
3. Dilates bronchi
4. Dilates arteries
ii. Phenylephrine (Neo-Synephrine)
1. Pure alpha
2. No cardiac stimulation
3. Little or no bronchoconstriction
4. Vasoconstriction
iii. Epinephrine
1. Combination alpha and beta
2. Predominately beta
3. High dose alpha effects
iv. Norepinephrine
1. Predominantly alpha
v. Dopamine (Intropin)
1. Low dose dopaminergic
2. Middle beta
3. High alpha
vi. Metaraminol (anamine)
1. Pedominately alpha
vii. Metaprotarenol (alupent)
1. Beta
c. Sympathetic blockers
i. Block sympathetic agents by beating them and occupying
receptor sites
1. Inderal
a. Sympathetic beta blocker (sympatholytic)
b. Opposes beta effects
c. Slow heartrate
d. Prevents vasodilation and bronchodilation
2. Atropine
a. Parasympathetic blocker (parasympatholytic)
b. Accelerates heart rate
ii. Indication of stimulating or blocking agents
1. Epinephrine
2. Norepinephrine
3. Isuprel
4. Dopamine
Thanks to Michael Vance for this document!