Preheat the oven to 400 degrees. Lightly coat the inside of muffin-pan cups with nonstick cookware spray.

Whisk together the all-purpose flour, whole-wheat flour, baking powder, baking soda, salt, cinnamon and nutmeg. Toss the blueberries with 2 teaspoons of the flour mixture and set aside.

Beat the butter in the large bowl of an electric mixer on moderate speed for 4 minutes. Add the sugar, increase the speed to moderately high and beat for 2 minutes. Beat in the egg and vanilla extract. Beat in the mashed bananas (the mixture will look slightly curdled), half the flour mixture, the buttermilk, then the balance of the flour mixture. By hand, fold in the blueberries.

Divide the batter among the muffin cups. Bake the muffins in the preheated oven for about 20 minutes, or until plump and a wooden pick inserted in the center withdraws clean.

Let the muffins stand in the pan on a cooling rack for 4 to 5 minutes, then carefully remove them to another rack.