The rectum has an intrinsic nervous mechanism represented by the enteric nervous plexus (ENP) and an extrinsic one mediated by the parasympathetic nerves. Rectal distension evokes the rectoanal inhibitory reflex, which acts through the ENP and is considered the main mechanism responsible for defecation.
Is defecation controlled by parasympathetic?
21.1 Definition. The defecation reflex is an involuntary reflex. These reflexes are controlled by the autonomic nervous system. The two major reflexes for defecation are the parasympathetic defecation reflex and the intrinsic myenteric defection reflex.
How does the nervous system help defecation?
As the rectal walls expand with filling, stretch receptors from the nervous system, located in the rectal walls, stimulate the desire to defecate. The urge passes within one to two minutes if not relieved, and the material in the rectum is then often returned to the colon where more water is absorbed.
What receptors are involved with defecation?
When enough stool moves to the rectum, the amount of stool causes the tissues in the rectum to stretch or distend. Inside these tissues are special “stretch” receptors designed to signal the brain when they are stretched. The defecation reflex triggers the two main sphincters around the anal canal.
Does the spinal cord control defecation?
In the spinal cord, control of the colorectum is relayed through the sacral spinal defecation centre [15, 16] and control of the external sphincter is relayed through Onuf’s nucleus in the sacral cord . Signals from the spinal defecation centre direct movements of the wall of the gut to cause bowel emptying (Fig.
Which spinal nerve controls bowels?
The hypogastric nerve sends out sympathetic innervation from the L1, L2, and L3 spinal segments to the lower colon, rectum, and sphincters.
What part of the spine controls bowel?
Bowel function is maintained by the nerves entering the spinal cord. It is the nerves which enter at the lower part of the spine which are responsible for the voluntary communication of the bowel.
What level of the spinal cord controls the bladder and bowel?
The lowest part of the spinal cord is the sacral spinal cord. Bladder function, bladder and bowel external sphincters, sexual functions (including erections and ejaculation in men and responsiveness in women), and some leg muscles are the domain of the sacral spinal cord.