Any knot in $S^3$ may be reduced to a slice knot by crossing changes, in other words a homootpy. Indeed, this slice knot can be taken to be the unknot. During this talk I shall ask when the same holds for knots in a homology sphere. I will prove that that a knot in a homology sphere is nullhomotopic in a smooth homology ball if and only if that knot is smoothly concordant to a knot which is homotopic to a smoothly slice knot. As a consequence, we prove that the equivalence relation on knots in homology spheres given by cobounding immersed annuli in a homology cobordism is generated by concordance in homology cobordisms together with homotopy in a homology sphere.