If you're good with physiology ask the doctor about what is actually going on. Ask him if the mechanism you learned is applicable etc. Read up some literature about his type of practice and come in prepared. One of the doctors I shadow loves to discuss the physiology behind every case and loves to ask you what is going on.
ex) Doctor: So *****wipe (you, me, any premed...just kidding), what do you think about keeping this hypertensive patient on her 1st generation beta blockers? Mind you, this is an Ob, this woman is 30+ weeks pregnant, and also has had a history of preterm labor
You: Well, I believe the older beta blockers are non selective, so while yes this would help lower her BP, wouldn't this also block the adrenergic receptors on her uterus? I would think we would want to keep her uterus relax? At this point ramble about beta 1 vs beta 2 receptors, newer beta blockers, calcium channel blockers etc.
Every doctor might not want to talk, some might love it. Try to be smart, gauge their reaction. Obviously they know you're not a doctor yet or hell even a resident. If you show some interest though they may take you more seriously or provide you with more opportunities