cursor in a procedure & transaction

Hello everyone!
I have a doubt about the use of the cursor.
I had a procedure by which, according to a parameter, decide whether to retrieve the data from Table A or from Table B, and in both cases, processes the data in the same way, so I decided to use two cursor. I did a test and saw that the cursor query returned to the procedure some records that were inserted after the execute of the procedure. Hence, my question: when I open a cursor within a procedure, I will open a new transaction or it's used the same transaction of the procedure?

My procedure is something like this:

CREATE PROCEDURE myprocedure
AS
declare variable v_1 integer;
declare variable v_2 integer;

DECLARE cursor1 CURSOR FOR (
  SELECT field1, field2
  FROM tableA
  WHERE...
  );
DECLARE cursor2 CURSOR FOR (
  SELECT field1, field2
  FROM tableB
  WHERE...
  );
BEGIN

  ...SOME instruction...

  IF (v_param IS NULL) THEN
    OPEN cursor1;
  ELSE
    OPEN cursor2;

  WHILE (0=0) DO
    BEGIN
      IF (v_param IS NULL) THEN
        FETCH cursor1 INTO :v_1, :v_2;
      ELSE
        FETCH cursor2 INTO :v_1, :v_2;

      IF (ROW_COUNT = 0) THEN
        BEGIN
          IF (v_param IS NULL) THEN
            CLOSE cursor1;
          ELSE
            CLOSE cursor2;

          LEAVE;
        END
      ELSE
        BEGIN
          ...SOME instruction...
        END
    END
  ...SOME instruction...
END


something  wrong?
Thanks!