Final answer:
Buprenorphine acts as a partial agonist and antagonist at the mu opioid receptor, providing pain relief and withdrawal symptom reduction while blocking other opioids' effects.
Step-by-step explanation:
The terms that best describe buprenorphine's action at the mu opioid receptor are partial agonist and antagonist. As a partial agonist, buprenorphine binds to the receptor and elicits a response but it is not as strong as that prompted by full agonists, such as morphine or heroin. This partial activation can reduce pain and withdrawal symptoms without producing the same level of euphoria or respiratory depression, which is why it is useful in opioid addiction treatment. As an antagonist, buprenorphine also has the ability to block other opioids by occupying the mu opioid receptors, preventing them from producing their effects and this characteristic is beneficial for preventing relapse in addicted individuals.