The answer is capillary venules. The hormones are also used to treat superficial bleeding because the resultant vasoconstriction reduces blood flow in the venules, hence reduce bleeding. The hormones are also used to increase blood pressure and treat anaphylaxis. The hormones induce constriction when bound to alpha adrenergic receptors such as the capillary venules. They cause dilation when bound to beta-adrenergic receptors such as in arteries.
<span>Systemic arterioles are the vessels that vasoconstrict in response to epinephrine and norepinephrine. Epinephrine is a hormone called adrenaline which is secreted by adrenal glands and when this secretion happens there is an increase in the hearth rate, blood pressure and metabolism and norepinephrine serves as a neurotransmitter in the central nervous system and sympathetic nervous system.</span>
