Emmanuel Adebayor produced a stunning early finish to pile the pressure on Newcastle boss Sam Allardyce.
To their credit, the Magpies made a fist of it and went close through skipper Geremi on five minutes and defender Steven Taylor 10 minutes before the break.
St James' erupted for the first time, Arsenal started to look edgy, and Sagna was booked for simulation after going down under Smith's challenge.
Smith flicked a header over from Geremi's 65th-minute throw-in as the home side remained on the front foot. The home side went close to snatching victory through Taylor in the dying minutes, but ultimately had to settle for a point.