Gastrointestinal motility

Question 1

Which part of the GI tract contains glands

Answer 1

Submucosa

Question 2

What is the inner circular muscle function

Answer 2

Orientated in a circular pattern so mixing function

Question 3

What is the outer longitudinal muscle function

Answer 3

Longitudinal so moving contents function

Question 4

What plexus is responsible for secretions I the GI tract

Answer 4

Submucosal plexus

Question 5

What plexus is responsible for movement in the GI tract

Answer 5

Myenteric plexus

Question 6

What are the pacemaker cells in the GI tract called

Answer 6

Interstitial Cells of Cajal

Question 7

How do Interstitial Cells of Cajal cause muscle tension

Answer 7

Initiate a spreading basal electrical rhythm (BER). There is a slow wave and the longer it spends above the threshold, the more spike potentials so there is a greater contraction force.

Question 8

How does peristalsis occur

Answer 8

Chyme activates receptors. Sends a message upstream and downstream of food bolus.

Upstream: ACh is released which depolarises smooth muscle cells so they are closer to spoke potentials.

Downstream: Release VIP. Decreases slow wave production of ICCand hyperpolarisation of SM cells so further away from threshold so no contraction

Question 9

What does parasympathetic nerve activation do to GI motility

Answer 9

Promotes increased motility

Question 10

What does sympathetic nerve activation do to GI motility and how

Answer 10

Decreased motility

• > noradrenaline activates beta adrenoceptorson smooth muscle cells so cells hyper polarise and move further away from threshold
• > Indirectly by decreasing Ach release via A2 adrenoceptors

Question 11

What is the zone of elevated pressure (ZEP)

Answer 11

prevents transit from one region to another

Question 12

Where is the ZEP found in the oesophagus

Answer 12

In lower oesophageal sphincter of stomach (area of intense contraction)

Question 13

What is the primary wave of oesophageal peristalsis controlled by

Answer 13

Vagus nerve

Question 14

What initiates the peristaltic wave

Answer 14

Mechanoreceptors in pharynx detect food bolus initiates peristaltic wave

Question 15

What happens if food is not projected to stomach after first peristaltic wave

Answer 15

Secondary wave of peristalsis is initiated by local ago-vagal reflexes

Question 16

What are peristaltic waves like on an empty stomach vs a full stomach

Answer 16

Weak
1st hour- theiyre weak and the pyloric sphincter is closed

Later, peristaltic waves are associated with mixing of gastric contents and emptying some contents into the duodenum

Question 17

What is the purpose of gastric contractions

Answer 17

Mixing of gastric contents and emptying some of the contents into the duodenum

Question 18

Neural control of stomach

Answer 18

Vagal relaxatory fibres induce relaxation (stimulated by oesophageal and gastric distension)

• mediated by VIP
• Supported by action of sympathetic nerves so inhibits release of Ach

Question 19

What increases gastric motility

Answer 19

Vagal fibres releasing ACh

Question 20

Stimulatory hormones

Answer 20

Gastrin (antrum)

Motilin (small intestine)

Question 21

Inhibitory hormones

Answer 21

gastrin (proximal stomach)
Secretin
CCK
NO

Question 22

What does the rate at which gastric contents pass into the duodenum depend on

Answer 22

Meal composition 
Meal volume
FRagment size
Osmolarity (osmolarities of chyme greater and smaller than certain value slow gastric emptying)
Acid (excess acid slows)
Fat (in upper small intestine slows)

Question 23

Two types of muscular contraction in small intestine:

Answer 23

Segmenting contractions

Peristaltic contractions

Question 24

What is segmenting contraction

Answer 24

Occurs in circular muscle and serves a mixing function (secretions from pancreas and liver with chyme)

Question 25

What are peristaltic contractions

Answer 25

More longitudinal

• occurs after meal
• MMC (strong wave of peristalsis typically after you’ve eaten to prepare room for food you’re just about to receive in small intestine)