Extensor pollicis longus muscle

The video tutorial explains the extensor pollicis longus muscle, which is responsible for the thumbs up movement. It originates from the ulna and interosseous membrane, extending to the thumb's distal phalanx. The muscle extends the thumb at the metacarpophalangeal and interphalangeal joints, creating the thumbs up curve. The posterior interosseous nerve, a branch of the radial nerve, supplies motor innervation to this muscle.

Describe the movement created by the contraction of the extensor pollicis longus muscle.

Which nerve supplies motor innervation to the extensor pollicis longus muscle?