الفهرس 
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Abstract
The autonomic nervous system may be considered as having a
dual function. The first function is to maintain the internal environ-
ment of the body in a state that encourages optimal function of the
various organ systems. The second function is to prepare the body to
undertake extra-ordinary efforts in situations that threaten the body.
Classically, two divisions of autonomic nervous system have
been described. The parasympathetic nervous system which can be
conceived as restorative system either before or after the stress&
the sympathetic nervous system which prepare the body forfight or flight.
Most of the sympathomimetic drugs in use today have mixed
cc and B stimulating properties. Only the B-agonist isoproterenal and
the cc agonist phenylephrine and methoxamine are relatively pure
drugs. The endogenous catecholamines are a perfect exam pIe. Dopamine
has ~1 - B1-, and dopamine receptor mediated effects. The dopamine
receptors are specifically activated by low doses of dopamine. Higher
doses of dopamine agonize first B-receptors and then, at higher
doses still, cc receptors. The other sympathomimetic arm nes all have
mixed actions in two respectsdoses still, a:: receptors. They
have both a direct action on the receptor as well as the affect noted
for dopamine of releasing endogenous norepinephrine. The three most commonly used synthetic sympathomimetic, mephentermine
(Wyamine), ephedrine and metaraminol (Ar ami ne) all have prominent
indirect effect, although the former two agents are also direct-acting
drugs. A major prolbem in modern cardiovascular intensive care is
the support of the failing or ischemic heart without producing either
marked tachycardia or peripheral vasodilation.