While doing sigmoidoscopy, if the rectum is inflated with gas increased peristalsis is seen in :

C i.e. Distal colonThere are two types of defecation reflex.Intrinsic reflex mediated by local enteric nervous systemParasympathetic defecation reflex mediated by sacral segment of the spinal cord.In both these types, the reflex is initiated by distention of the rectum by the feces and causes increased peristalsis in the descending colon, sigmoid colon and rectum. This forces the feces toward the anus.In a similar way, when the rectum is inflated with gas (CO2) in sigmoidoscopy, nerves are stimulated and causes increased peristalsis in the descending colon, sigmoid (distal colon)Q and rectum.