Study Set Content:
Effects of Alpha 1-Receptor Activation
• Alpha 1 receptors are widely expressed in vascular beds,
Increased BP
A relatively pure a agonist such as phenylephrine increases peripheral arterial resistance and decreases venous capacitance.
• Mydriasis
• Increased closure of internal sphincter of the bladder. B. Effects of Alpha 2-Receptor Activation
Effects of Alpha 2-Receptor Activation
• Alpha 2 adrenoceptors are present in the vasculature, and their activation leads to
vasoconstriction.
This effect is observed only when a 2 agonists are given locally, by rapid intravenous injection or in
very high oral doses.
these vascular effects are obscured by the central effects of a 2 receptors, which lead to inhibition of sympathetic tone and blood pressure.
When given systemically
are used as sympatholytics in the treatment of hypertension.
A 2 agonists
In patients with pure autonomic failure, characterized by neural degeneration of postganglionic noradrenergic fibers,____ may increase blood pressure because the central sympatholytic effects of clonidine become irrelevant, whereas the peripheral vasoconstriction remains intact.
clonidine
Effects of Beta-Receptor Activation
• The blood pressure response to a ß-adrenoceptor agonist depends on its contrasting effects on the
heart and the vasculature
increases cardiac output by increasing. contractility and by direct activation of the sinus node to increase heart rate.
Stimulation of Bẞ receptors in the heart
Beta agonists also decrease peripheral resistance by activating (blank), leading to vasodilation in certain vascular beds
ẞ 2 receptors
is a nonselective ß agonist; it activates both B 1 and 32 receptors.
Isoproterenol
The net effect is to() systolic pressure and to () diastolic pressure, so that mean blood pressure is decreased
maintain or slightly increase, lower
Effects of Dopamine-Receptor Activation
• Intravenous administration of ____ promotes vasodilation of renal, splanchnic, coronary, cerebral, and perhaps other resistance vessels, via activation of D. receptors.
dopamine
Activation of the D, receptors in the renal vasculature may also induce
natriuresis.
The renal effects of dopamine have been used clinically to improve perfusion to the kidney in situations of ____(abnormally low urinary output).
oliguria
The activation of ____, receptors suppresses norepinephrine release, but it is unclear if this contributes to cardiovascular effects of dopamine. Noncardiac Effects of Sympathomimetics
presynaptic D
NONCARDIAC EFFECTS OF SYMPATHOMIMETICS
• Adrenoceptors are distributed in virtually all
organ systems.
Activation of B 2 receptors in bronchial smooth muscle leads
bronchodilation
B, agonists are important in the treatment of
asthma.
In the eye, the radial pupillary dilator muscle of the iris contains a receptors; activation by drugs such as phenylephrine causes
mydriasis.
In genitourinary organs, the bladder base, urethral sphincter, prostate contain a receptors that mediate contraction and therefore promote
urinary continence.
