Ureteric peristalsis is due to

Ureteric peristaltic contractions occur 1 to 5 times per minute. There are specialized smooth muscle pacemaker cells in region of renal pelvis; the contractions arise here. Ureters are innervated by sympathetic and parasympathetic nerves. Peristaltic waves may be modified by the action of splanchnic nerves (upper poion of ureter) and by hypogastric plexus (lower poion). Ureteral smooth muscle acts as a functional syncytium, it is an example of unitary smooth muscle. Mechanical stimuli (stretch) or chemical stimuli may trigger APs which are of "plateau" type.