Vasoconstricting Agents
Epinephrine and
norepinephrine are secreted by the adrenal
medulla when the sympathetic nervous system is stimulated. All
vascular beds of the body are affected by these vasoconstricting
agents. Another, angiotensin, is one of the most powerful
vasoconstricting agents. A decrease in arterial pressure will
cause the kidneys to secrete 
renin, which in turn acts to split
away angiotensin from its precursor, angiotensinogen.
Vasopressin
(also called anti-diuretic hormone) formed in the hypothalamus,
is a very powerful vasoconstrictor but also helps the body
regulate fluid volume by controlling water reabsorption in the
renal tubules.
Epinephrine and
norepinephrine are secreted by the adrenal
medulla when the sympathetic nervous system is stimulated. All
vascular beds of the body are affected by these vasoconstricting
agents. Another, angiotensin, is one of the most powerful
vasoconstricting agents. A decrease in arterial pressure will
cause the kidneys to secrete 
renin, which in turn acts to split
away angiotensin from its precursor, angiotensinogen.
Vasopressin
(also called anti-diuretic hormone) formed in the hypothalamus,
is a very powerful vasoconstrictor but also helps the body
regulate fluid volume by controlling water reabsorption in the
renal tubules.