There are different types of neurons involved in innervating the lower GI tract these include: the enteric nervous system; located within the wall of the gut, and the extrinsic nervous system; comprising sympathetic and parasympathetic innervation. The enteric nervous system directly controls the gut motility, whereas, the extrinsic nerve pathways influence gut contractility indirectly through modifying this enteric innervation. In almost all cases of<unk>  it is the extrinsic nervous supply affected and the enteric nervous supply remains intact. The only exception being Parkinson's disease, as this can affect both the enteric and extrinsic innervation. Defecation involves conscious and subconscious processes, when the extrinsic nervous system is damaged either of these can be affected. Conscious processes are controlled by the somatic nervous system, these are voluntary movements for example the contraction of the striated muscle of the external anal sphincter is instructed to do so by the brain, which sends signals along the nerves innervating this muscle. Subconscious processes are controlled by the autonomic nervous system; these are involuntary movements such as contraction of the smooth muscle of the internal anal sphincter or the colon. The autonomic nervous system also provides sensory information; this could be about the level of distension within the colon or rectum.
Neurogenic bowel dysfunction
Functional constipation
Obstructed defecation
Sphincter of Oddi dysfunction
Sphincter paralysis
Rectal foreign body
Athletic incontinence
Rectal prolapse