Denis Hurley 1 Try
Gerhard van den Heever 2 Tries
Ronan O'Mahony 1 Try
Plymouth Albion remain top of the group after their 39-3 win over Stirling at Brickfields and Munster A now need to beat Stirling away next week to qualify for the last eight.
Both sides traded early penalties with Johnny Holland kicking Munster A into an early lead before his Nottingham counterpart Matt Jarvis made it 3-3 with both penalties coming from infringements in the scrum.
The impressive Ivan Dineen set up the first try after 16 minutes as he burst through a gap in midfield before popping it back inside to Denis Hurley who touched down under the posts with Holland adding the conversion.
Dineen was replaced by Cian Bohane after he picked up an ankle injury not long afterwards.
Van den Heever opened his try-scoring account with Munster A on 23 minutes as he pounced on a loose Nottingham pass on their left touchline well inside his own half and he raced away to touch down in the corner.
Holland was unsuccessful with the difficult conversion but Munster A were in complete control and leading 15-3.
Then slowly but surely that lead began to slip as Jarvis, who had clearly brought his kicking boots, took advantage of Munster indiscipline to kick three penalties before half-time to make it 15-12 at the break.
Another Jarvis penalty on 43 minutes brought the sides level but an injury to Tom Price halted proccedings for ten minutes as the medical staff took all the precautions and Price was stretchered off to warm applause from the crowd.
With the pressure on, Munster A knew they needed to produce and Holland edged them back in front with a penalty before Ronan O'Mahony was on the spot to extend the lead when he dived on Holland's perfect chip through the Nottingham defence to touch down.
Holland added the extras to O'Mahony's fifth try in five B&I Cup games this season to make it 25-15.
As the game drifted past the 80 minute mark it looked like four points would be the reward for their efforts but the exceptional Barry O'Mahony, who captained the side, broke down the right wing in the last play of the game and fed van den Heever who streaked into the corner for the fourth try.
Holland was off target with the conversion but the bonus point was secured to set up a grandstand finish to the pool next Saturday.
Munster A: Ronan O'Mahony; Gerhard van den Heever, Ivan Dineen (Cian Bohane 24), Denis Hurley, Darren Sweetnam; Johnny Holland, Gerry Hurley (Brian Haugh 70); Alan Cotter, Ger Slattery, John Ryan; Ian Nagle, Darren O'Shea; Dave O'Callaghan (Shane Buckley 70), Barry O'Mahony (Capt), Paddy Butler. Replacements: Max Abbott, Brian Scott, Shane Buckley, Jack O'Donoghue, Brian Haugh, Rory Scannell, Cian Bohane.
Nottingham: Andrew Savage; Olly Woodburn, George Catchpole, Joe Munro, Ryan Hough; Matthew Jarvis, Sean Romans; Ryan Bower, Alun Walker, Harry Williams; Tom Price, Dan Montagu; Kiefer Laxton, Brent Wilson (Capt), Tom Calladine. Replacements: Campese Ma'afu, Harry Thacker, Michael Holford, Neilus Keogh, Finlay Barnham, Rory Lynn, Jacob Knight.