Regulation of Motility

Question 1

What are the functions of the small intestine?

Answer 1

Mixing of digestive juices
Nutrient absorption
Movement of chyme from small to large intestine

Question 2

What are spontaneous contractions?

Answer 2

Contractions of the smooth muscle that occur after eating

Question 3

What modulates spontaneous contractions?

Answer 3

Neurotransmitters and hormones

Question 4

What are migrating motor complexes?

Answer 4

Regular smooth muscle contractions

Question 5

Describe segmentation

Answer 5

The contraction of a smooth muscle ring and relaxation of adjacent rings which allows for rhythmic division of chyme

Question 6

Describe peristalsis

Answer 6

Sequential contraction of smooth muscle alone the intestine that pushes chyme along

Question 7

Where does most segmentation occur?

Answer 7

Duodenum

Question 8

What regulates segmentation and peristalsis?

Answer 8

Intrinsic neural plexuses
Autonomic innervation
Peptides which increase motility and decrease reflexes

Question 9

Describe the distension reflex

Answer 9

Pressure receptors are stimulated which inhibits motility

Question 10

Describe the ileogastric reflex

Answer 10

Distension in the ileum or stomach causes relaxation in the stomach or ileum

Question 11

What sort of circuit is the ileogastric reflex?

Answer 11

Feedforward

Question 12

Trauma to which organs may inhibit motility?

Answer 12

Kidneys or gonads

Question 13

What are the four types of laxatives?

Answer 13

Secretory
Osmotic
Emollient
Bulk forming

Question 14

Describe the mechanism of secretory laxatives

Answer 14

Increases intestinal secretions to increase lubrication

Question 15

Give an example of a secretory laxative

Answer 15

Senna, bisacodyl, glycerol, sodium picosulfate

Question 16

Describe the mechanism of osmotic laxatives

Answer 16

Increase water absorption into the gut to increase lubrication

Question 17

Give an example of an osmotic laxative

Answer 17

Lactulose, macrogol 3350, magnesium sulfate

Question 18

Give an example of an emollient laxative

Answer 18

Docusate sodium, arachis oil, liquid paraffin

Question 19

Describe the mechanism of an emollient laxative

Answer 19

Increases lubrication

Question 20

Describe the mechanism of a bulk forming laxative

Answer 20

Increases bulk of contents to make peristalsis more likely

Question 21

Give an example of a bulk forming laxative

Answer 21

Ispaghula husk, sterculia, bran, methylcellulose

Question 22

What other agents may be given to increase motility?

Answer 22

Cholinergic agonists

Acetylcholine esterase inhibitors

Question 23

What controls the ileocaecal sphincter?

Answer 23

Distension of the distal ileum

Question 24

What occurs in the large intestine?

Answer 24

Water absorption

Question 25

What is the taeniae coli?

Answer 25

The three layer muscle band in the colon

Question 26

What is the haustre?

Answer 26

Tight, dynamic muscular bands in the colon

Question 27

What causes mixing in the colon?

Answer 27

Formation and reformation of haustres

Question 28

Describe colonic propulsion

Answer 28

Sequential haustration propelling matter

Peristalsis towards the rectum

Question 29

What regulates motility in the large intestine?

Answer 29

Spontaneous contractions of smooth muscle
Nervous regulation
Reflexes

Question 30

Describe the colonocolonic reflex

Answer 30

Distension in the proximal large intestine causes relaxation in the distal large intestine

Question 31

Describe the gastrocolonic reflex

Answer 31

Presence of chyme in the stomach causes propulsion in the large intestine

Question 32

Describe the process if defaecation

Answer 32

Distension of rectum activates pressure receptors which is reinforced by parasympathetic afferents
Somatic relaxation of the external anal sphincter