Really helpful mneumonic for the brachial plexus.
3 MUSketeers Assasinated 5 Mice, 5 RAts, and 2 Unicorns
(musculocutaneous comes off C5, C6, and C7. Axillary comes of C5 and C6. Median comes off all 5. Radial comes off all 5, and Ulnar comes of C8 and T1.)
Watch the video. This will make more sense.