The Lilywhites played for the best part of an hour with 10 men after Liam Lindsay was sent-off for bringing down Tom Lawrence when the Rams midfielder was through on goal.
It became a 10 v 10 clash in the 55th minute when Max Bird’s high challenge on Ben Whiteman earned the Derby man a red card.
With both a full quota of players and one less, North End were below par and it looked like a point was the most they could hope for.
As an attacking force, PNE offered very little, a couple of shots from corners the best they had to offer.
Derby weren’t great by ant stretch but always looked to have the edge in the game and will feel they were deserving of the three points.
North End started in a 4-3-3 formation, a departure from the 3-5-2 usually employed by Ryan Lowe.
Lindsay was in the centre of defence next to Patrick Bauer, with Joe Rafferty at right-back and Andrew Hughes on the left.
Ched Evans started up front with Emil Riis to his right and Cameron Archer to the left.
The visitors had a bright opening few minutes and could have been ahead inside 90 seconds when Ben Whiteman pulled a corner low into Daniel Johnson’s path in the box.
Johnson’s shot was blocked by a defender, with Johnson and Evans getting in one another’s way as they went for the rebound.
Two crosses from Hughes led to headed chances for Archer and Riis, both of which went harmlessly wide.
Derby began to find their way back into the contest, Jason Knight’s shot from 20 yards after space had opened up in front of him, pushed behind by Iversen diving to his right.
Lawrence glanced a header across goal and just wide of the far post after being found by Malcolm Ebiowei’s cross from the right.
Whiteman had a shot charged down in the box after being found by Johnson’s corner, the midfielder chasing the loose ball and lifting it back into the middle where Lindsay’s header was saved by keeper Ryan Allsop.
Lindsay’s next involvement was to end with him getting a red card.
He stumbled as he moved to meet a back header from Alan Browne, that allowing Lawrence to steal in front of him just outside the box.
Lindsay pushed Lawrence in the back as he tried to recover and the Wales international went to ground, referee Geoff Eltringham reaching for his back pocket to pull out the red card.
Lawrence curled the resulting free-kick past the far post and PNE then reorganised, bringing on Sepp van den Berg in place of the sacrificed Riis.
They switched to a 3-4-2 system, Van den Berg, Bauer and Hughes in a back three, with Rafferty and Johnson in the wing-back roles.
Just before half-time, Evans drove a shot from the left hand side of the box into the side-netting although PNE felt they should have a free-kick just before for a foul on Archer on the edge of the box.
Eight minutes into the second half, Derby broke on the counter-attack, Lee Buchanan seeing his low shot saved by Iversen with an out-stretched foot.
The numbers were evened-up in the 55th minute when Bird launched himself into a forceful challenge on Whiteman near to the centre-circle.
Bird’s leading leg was quite high and Mr Eltringham deemed the tackle out of control as he pulled out the red card for the second time.
The game became scrappy to say the least at 10 v 10. Johnson saw a shot from the edge of the box take a big deflection and fall just wide of the target.
Derby broke the deadlock in the 81st minute, winning a corner on the right after Lawrence’s shot was pushed behind by Iversen.
Lawrence’s corner was met by Curtis Davies at the far post, his header saved on the line by Iversen. The Danish keeper managed to block the follow-up attempt from Luke Plange which came out of a sea of legs.
North End failed to clear their lines properly and Morrison rifled home a shot from 10 yards.
It could have been 2-0 two minutes later but Iversen saved superbly with his feet from Morrison.
Derby: Allsop, Byrne, Davis, Chasin, Buchanan, Bird, Knight, Ebiowei (Morrison 68), Ebosele (Bielik 58), Lawrence, Plange (Stearman 85). Subs (not used): Roos, Forsyth, Sibley, Cybulski.
PNE: Iversen, Rafferty, Bauer, Lindsay, Hughes, Whiteman, Browne, Johnson, Archer (Murphy 75), Riis (Van den Berg 34), Evans (Maguire 65). Subs (not used): Ripley, McCann, Sinclair, Potts.
Referee: Geoff Eltringham (County Durham)
Attendance: 23,600 (1,500 PNE)