Nerve Supply of the Rectum (large intestine) Flashcards
(16 cards)
What is the role of the parasympathetic nervous system in the rectum?
The parasympathetic nervous system, through the pelvic splanchnic nerves (S2–S4), stimulates peristalsis (muscle contractions) in the rectum and relaxes the internal anal sphincter, allowing for the movement of faeces into the anal canal.
What happens to the internal anal sphincter when the parasympathetic nerves are activated?
The parasympathetic nerves relax the internal anal sphincter, allowing faeces to pass from the rectum into the anal canal.
What is the effect of sympathetic nerve supply in the rectum?
The sympathetic nerves, coming from the lumbar splanchnic nerves, contract the internal anal sphincter and inhibit peristalsis in the rectum, which helps in the storage of faeces and prevents defecation until it is appropriate.
What role does the somatic nervous system play in the rectum?
The somatic nervous system provides voluntary control through the pudendal nerve over the external anal sphincter, allowing conscious control of defecation.
How does the rectum signal the brain that it is full?
The rectum has stretch receptors in its walls that detect when it is full. These receptors send signals to the brain, which then triggers the urge to defecate.
What is the role of the pudendal nerve in the rectum?
The pudendal nerve, which is part of the somatic nervous system, controls the external anal sphincter. It allows voluntary control over defecation, giving the ability to hold in faeces until the person is ready to defecate.
What happens when the sympathetic nerves are activated in the rectum?
When sympathetic nerves are activated, they contract the internal anal sphincter, which prevents defecation by keeping faeces inside the rectum. They also inhibit peristalsis to reduce movement in the rectum.
What happens to the external anal sphincter during defecation?
During defecation, the external anal sphincter is relaxed voluntarily through the pudendal nerve, allowing faeces to be expelled from the body.
How do parasympathetic pelvic splanchnic nerves (S2-S4) affect the rectum?
Parasympathetic pelvic splanchnic nerves (S2–S4) stimulate peristalsis in the rectum, helping move faeces toward the anal canal. They also relax the internal anal sphincter, allowing faeces to pass into the anal canal during defecation.
What role does the lumbar splanchnic nerve play in the rectum?
The lumbar splanchnic nerves, which are part of the sympathetic nervous system, inhibit peristalsis in the rectum and contract the internal anal sphincter, helping to store faeces and prevent defecation until it is appropriate.
How does the rectum’s nervous system coordinate defecation?
Parasympathetic nerves (pelvic splanchnic nerves) stimulate peristalsis and relax the internal anal sphincter.
Sympathetic nerves (lumbar splanchnic nerves) inhibit peristalsis and contract the internal anal sphincter.
Somatic nerves (pudendal nerve) control the external anal sphincter, allowing voluntary control over defecation.
What is the function of the stretch receptors in the rectum?
The stretch receptors in the rectal wall detect when the rectum is filled with faeces. They send signals to the brain, triggering the defecation reflex, which results in the relaxation of the internal anal sphincter and initiation of defecation.
What happens to the rectum during the rectoanal inhibitory reflex?
When faeces enter the rectum, the rectoanal inhibitory reflex causes the internal anal sphincter to relax involuntarily, allowing faeces to move into the anal canal. This reflex is essential for preparing the body for defecation.
What is the significance of the pudendal nerve in controlling the external anal sphincter?
The pudendal nerve allows voluntary control over the external anal sphincter. This gives the individual the ability to hold in faeces and decide when to defecate, providing control over bowel movements.
How do the sympathetic and parasympathetic nerves work together in the rectum?
The sympathetic nerves help with storage of faeces by contracting the internal anal sphincter and inhibiting peristalsis.
The parasympathetic nerves stimulate peristalsis and relax the internal anal sphincter during defecation to help expel faeces.
How does the parasympathetic nervous system help initiate defecation?
The parasympathetic nervous system (pelvic splanchnic nerves, S2–S4) triggers peristalsis in the rectum and relaxes the internal anal sphincter, allowing faeces to move into the anal canal for elimination.
