Lower esophageal sphincter
Lower esophageal sphincter (LES) The resting pressure is about 20 mm Hg. Basal tone regulated by both intrinsic and extrinsic nerves, and hormones. A significant fraction of this basal tone is mediated by vagal cholinergic fibers (contraction of LES). Hence, options A & B are not correct. Stimulation of sympathetic nerves to the sphincter causes the LES to contract. Relaxation LES occurs in response to primary peristalsis in the esophagus is mediated by VIP and NO. Contraction of the diaphragm or increased intra-abdominal pressure will increase the pressure in LES. Option C is not correct.
Has no tonic activity
Has a tone which is provided by the sympathetic system
Relaxes on increasing abdominal pressure
Relaxes ahead of the peristaltic wave
Gastrointestinal System