Epinephrine and norepinephrine that are released from the adrenal glands affect target tissue for a longer period of time than the same substances released from neurons at their peripheral receptors. Why?
A) The adrenal gland releases larger amounts of the neurotransmitters than the neurons.
B) The hormones released from the adrenal glands bind to different receptors than those released from neurons.
C) There are no enzymes to break down epinephrine and norepinephrine in the blood and very little in peripheral tissues.
D) The effectors are less sensitive to epinephrine and norepinephrine released by the adrenal glands.
E) The epinephrine and norepinephrine from the adrenal glands are released by sympathetic neurons, whereas parasympathetic neurons release these substances at the effector organs.
Answer: C