Physiology- Motility Flashcards
Peristalsis: What is it a reflex response to? Is it dependent on extrinsic innervation? What 2 neurotransmitters stimulate muscle contraction? What 3 things cause muscle relaxation?
Stretch.
No!
Substance P and Ach (Muscarinic-R) contract muscle.
NO, VIP, ATP cause relaxation ahead stimulus.
Segmentation: How is it different from peristalsis? Is it dependent on central input?
Antero and retrograde movement (unlike peristalsis)-for efficient mixing.
No!
The BER is present in all segments except?
Esophagus and proximal stomach
What is the MMC? What initiates it? What 3 secretions increase during it? What does eating do to it?
Clears the stomach and intestine of luminal contents for next meal at regular intervals during fasting states.
Motilin.
Gastric, pancreatic and bile secretions.
Eating stops MMC, inhibits motilin, resumes peristalsis and BER.
What reflex is is a somatic motor reflex involving the CNS, but producing esophageal peristalsis.
Vagal Reflex Control of Peristalsis in Striated Muscle of the Esophagus.
What are the 3 features of esophageal motility?
- Swallowing
- Propulsion via peristalsis
- Relaxation of LES
What controls contraction and relaxation of the LES?
Contraction (LES is tonically contracted): Vagal cholinergic nerves (nicotinic, i.e. atropine insensitive) and Sympathetic nerves (alpha-adrenergic).
Relaxation: primary peristalsis –> inhibitory vagal nerve input to circular muscles of LES (neurotransmitters (VIP and NO) and reduced activity of vagal excitatory fibers (cholinergic, nicotinic).
What triggers primary peristalsis in the esophagus? Secondary?
Primary = swallowing reflex Secondary = distention
What is the functional motility of the proximal stomach?
(cardia, fundus, proximal body)
Serves as reservoir and moving the gastric contents. Tonic contractions in gastric emptying
What is the functional motility of the distal stomach?
(distal body, antrum)
Serves as grinding and triturating the meal.
Pylorus controls food exit
Pylorus relaxes during MMCs
What do the slow waves (BER) do?
- Slow waves only produce contraction when the threshold is achieved.
- Slow waves determine maximal rhythm of phasic contractions.
What is receptive relaxation (accommodation)? What happens if you have a vagotmoy or resect the proximal stomach?
Receptive relaxation increases compliance so that luminal pressure changes very little between the empty state (50 mL volume) and filled state (1500 mL volume).
You lose accommodation.
What regulates the force of contraction in the stomach?
Increased by gastric distension, via short reflexes and gastrin.
Inhibited by 1) duodenal distension, 2) appearance of fat, protein, acid or hypertonic chyme in the duodenum 3) increased sympathetic tone.
What does the pyloric valve regulate?
emptying and prevents regurgitation
What inhibits gastric emptying?
- Entry of chyme into duodenum
- Fat, protein digests in duodenum → ↑ CCK
- Acidity (pH < 3.5) in duodenum → ↑ secretin
- Hypo/hyper-osmotic chyme in duodenum
- Distention of duodenum
- Solids more inhibitory than liquids.
