For the next few questions, use these answer choices: a) Agonist b) Antagonist c) Up-regulation d...

For the next few questions, use these answer choices: a) Agonist b) Antagonist c) Up-regulation d) Down-regulation e) Desensitization 51) This kind of molecule binds to a receptor and blocks 52) A cell can become more responsive to a signal 53) One explanation for drug tolerance includes a loss of its activity. molecule by initiating a(n) of receptors. receptor affinity for its signal molecule, also known as 54) If levels of a signal molecule are abnormally low, a patient might be given a(n) for that signal molecule to return him or her to homeostasis.