Tennessee center Mercedes Russell (21) and Northwestern State guard Chelsea Rogers (12) battle for a rebound in their NCAA women's basketball first-round tournament game, Saturday, March 22, 2014, in Knoxville.

KNOXVILLE - Isabelle Harrison scored 12 points and sparked a game-changing 12-0 run as No. 1 seed Tennessee withstood an ailing head coach and a lethargic first-half performance to beat Northwestern State 70-46 in its NCAA tournament opener Saturday.

Tennessee coach Holly Warlick missed the Lady Vols' morning shootaround with what school officials described as a case of food poisoning. Warlick rejoined her team for the game, but she had an IV port in her left hand during the first half and sat on an orange stool while assistant coach Kyra Elzy stood and shouted instructions.

Warlick stood and was much more animated in the second half as Tennessee pulled away.

Northwestern State (21-13), seeking to become only the second No. 16 seed to beat a No. 1 seed, forced a 22-22 tie early in the second half before the Lady Vols (28-5) scored 12 straight points to seize control.