Gastrointestinal Physiology: Basics

Question 1

This is the sustained contraction for minutes to hours (eg., sphincters)

Answer 1

Tonic contractions

Question 2

These are waves of contraction and relaxation, each wave lasting seconds (eg., peristalsis)

Answer 2

Phasic contractions

Question 3

This is any pattern of contraction or relaxation of GI tract smooth muscle.

Answer 3

Motility pattern

Question 4

True or false. Retropulsion is a combination of two or more simpler motility patterns

Answer 4

True.

Question 5

True or false. Relaxation is not an example of a motility pattern.

Answer 5

False. Storage in the stomach is facilitated by relaxation motility patterns

Question 6

This is the general term for the motility pattern that specifically moves GI contents along the tract.

Answer 6

Propulsion

Question 7

GI motility is controlled by what type of muscle tissue?

Answer 7

Smooth muscle

Question 8

What does it mean by motility being spontaneously active?

Answer 8

It’s always contracting (doesn’t need external output)

And contains pacemaker cells to set the pace of contraction

Question 9

The strength of contractions are regulated by two types of input.

Answer 9

Nervous and hormonal input

Question 10

What is the generalised motility pattern when fasting?

Answer 10

Migrating motor complex, housekeeping (deals with unresolved secretions and any undigested content)

Question 11

What are the 3 main motility patterns in the feeding stage?

Answer 11

1) relaxation - for storage (in stomach and colon)
2) propulsion/peristalsis - in esophagus, stomach, small and large intestine
3) mixing/retropulsion/segmentation - stomach and small and large intestine

Question 12

What are the 2 motility patterns for mixing?

Answer 12

Retropulsion (stomach) and segmentation (small/large intestine)

Question 13

This is the motility pattern where circular muscles contract behind, to allow the longitudinal muscles ahead the bolus to contract.

Answer 13

Peristalsis

Question 14

This is the motility pattern where alternating segments of circular muscle expose the bolus of food to the surface of the small/large intestine to break the food up. (absorptive surfaces have the enzymes for digestion)

Answer 14

Segmentation

Question 15

What’s the difference between chewing and swallowing?

Answer 15

Chewing: reduces size of food; reflex control
Swallowing: rapid transfer of material from mouth to stomach; proceeds reflexively

Question 16

What motility pattern dominates the fundus and body of the stomach?

Additional question: what regulates this pattern?

Answer 16

Storage - relaxation

Nervous system - stimulation of the vagus nerve

Question 17

What motility pattern dominates in the antrum of the stomach?

Answer 17

Mechanical digestion: peristalsis/retropulsion and mixing: segmentation

Question 18

This allows controlled delivery to the duodenum of the small intestine.

Answer 18

Pyloric sphincter

Question 19

Gastric emptying is a combination of what 2 motility patterns?

Remember: gastric emptying refers to the emptying of the stomach into the duodenum of the small intestine.

Answer 19

Peristalsis and periodic opening of pyloric sphincter

Question 20

What are the main motility patterns in the small intestine between meals and after a meal?

Answer 20

Between meals: migrating motor complex

After meals: Segmentation (mixing) and peristalsis (propulsion)

Question 21

What are the main motility patterns of the large intestine?

Answer 21

Segmentation and propulsion (mass movement)

• peristaltic waves drives feces into rectum and initiates defecation

Question 22

This regulation is responsible for detecting content and releasing hormones.

Additional question: what are the cells that do this? (think of the system and then the gut)

Answer 22

Hormonal regulation

Enteroendocrine cells

Question 23

True or false. The motility pattern, relaxation, is able to contribute to storage by having a bigger volume with large changes in pressure.

Answer 23

False. Storage is achieved by bigger volume with minimal change in storage.

Question 24

Where is peristalsis initiated in the stomach?

Answer 24

Greater curvature of the stomach

Question 25

What are the 2 factors that affect gastric emptying?

Answer 25

Size of the meal and composition of the meal

Question 26

How does size of the meal affect gastric emptying?

Answer 26

The larger the meal the faster gastric emptying occurs (just think of when you have a big meal, and how quickly its digested)

Question 27

How does composition of the meal affect gastric emptying? (fluids, fats and acids specifically)

Answer 27

Some foods are easier to digest than others.

Fluids are faster than solids
Fats slow gastric emptying because need support of bile salts
Acids slow gastric emptying because they need to be neutralised

Question 28

How does the nervous system carryout long reflexes? (where does it act upon)

Answer 28

CNS acts upon myenteric plexus to augment ENS and create long reflexes.

Question 29

These cells detect content and release hormones.

Answer 29

enteroendocrine cells