GIT Movement: Types

Question 1

Stimulus of Propulsive movement (peristalsis

Answer 1

• Mechanical Distension
• Chemical/Physical irritation
• Strong parasympathetic signal (nervous)

Question 2

Describe Mechanism of peristalsis (propulsive movement)

Answer 2

1. Sensory neurone (sensing stimuli) secrete Serotonin onto Myenteric plexus, activating it
2. Myenteric plexus sends signal to Cholinergic neurones in retorgrade & anterograde directions:

Retrograde:
* Activate neurones that release Substance P & acetylcholine, causing contraction of smooth muscles (behind bolus of food)

Anterograde:
* Activating neurones secreting NO & VIP, causing relaxation of smooth muscles (ahead of bolus/stimuli)

Question 3

Control of peristalsis

Answer 3

• Nervous: by myentric plexus
• Hormonal: all hormones of the GIT except Glucagon & secretin

Question 4

evidence for control of peristalsis being done by Myentric plexus

Answer 4

in congenital absence of myentric plexus or Inhibition of myenteric plexus by Atropine, there is no/ weak peristalsis

Question 5

Mechanism of Mixing movement

Answer 5

(modified peristalsis & segmentation contractions)
* Peristaltic contractions with blocked sphincter foreward: causing churning instead of forward propelling
* Segmentation Contractions: Local Intermittent constrictive contractions lasting only between 5-30 sec, with new constritions occuring at the site between the previous 2 ones

Question 6

Control of Mixing Movements

Answer 6

• Slow waves (BER) from interstitial cells of Cajal
• Enteric Nervous system (Myenteric)

Question 7

MMC (migrating Motor Complex) occurs during

Answer 7

during fasting (in between meals)

Question 8

MMC is initiated by ____& immediately stops when ____

Answer 8

• Motilin hormone
• Food is ingested