Gastrointestinal Motility

Question 1

What are the four basic functions for the digestive system?

Answer 1

motility, secretion, digestionand absorption of ingested food

Question 2

which functions have the highest degree of control?

Answer 2

Secretion and motility

Question 3

what is gastric filling and how can the stomach achieve this?

Answer 3

It is the first step of gastric motility - and due to the plasticity of stomach muscles

Question 4

What initiates the storage and mixing phase of gastric motility?

Answer 4

Pacemaker cell in upper fundus - starts wave that moves out towards the pylorus region
it is modified by mechanical = stretch, hormonal = gastrin, and neural factors = vagus nerve

Question 5

what part of the stomach is responsible for mixing/grinding food particles?

Answer 5

The pyloric antrum region

Question 6

What is the third phase of gastric motility?

Answer 6

Gastric Emptying

Question 7

What factors increase gastric emptying?

Answer 7

Stomach = stretch, fluidity of chyme

Question 8

What factors decrease emptying?

Answer 8

Duodenum = fat, acid, hypertonicity, distension

Question 9

what are the mechanisms of control for gastric emptying?

Answer 9

1) receptors = pH, fat, osmolarity, stretch
2) Hormones = enterogastrones
- gastrin = pyloric antrum and duodenum
- secretin
- CCK
- GIP
3) Nerve pathways (intrinsic)
4) Nerve pathway (extrinsic)
- sympathetic = decreased emptying
- parasympathetic = increased emptying

Question 10

what are some of the stimuli for gastrin release?

Answer 10

• distension of stomach

- presence of protein or A.A in pyloric region of stomach

Question 11

Which enterogastrones stimulate an increase in gastric motility and emptying?

Answer 11

Gastrin

Question 12

Which enterogastrones stimulate a decrease in gastric motility and emptying?

Answer 12

CCK, Secretin, GIP

Question 13

What are the 3 forms of motility in the small and large intestines?

Answer 13

1) Segmentation
2) Migrating motor complexes (MMC)
3) Giant peristaltic contractions (mostly large intestine/colon)

Question 14

What do spasmolytics do?

Answer 14

bind to receptors and reduce gi tone and motility = blocks Ach - parasympathetic receptors on smooth muscles

Question 15

What is another drug that modifies GIT motility?

Answer 15

Prokinetics: “normalise” GIT motility so restore motility in “injured” gut
- more complex mechanism that isnt really that well understood yet

Question 16

what is the summary of gastric motility?

Answer 16

1) there is autonomous activity in GIT muscle

2) there is a hierarchy of control imposed on this autonomous activity

Question 17

What is the hierarchy of control imposed on the autonomous system?

Answer 17

1) receptors
2) hormones (enterogastrones)
3) Intrinsic nerves (pathways within the gut)
4) Extrinsic nerves (pathways involve CNS) = autonomic