Control of Gut , Motility

Question 1

What are the 3 main ways of controlling the gut ?

Answer 1

Autonomic nervous system
Enteric nervous system
Hormones and paracrine/neurocrine substances

Question 2

Which neurotransmitter is used at the ganglia (between pre and post fibres )

Answer 2

Acetylcholine

Question 3

Describe the sympathetic innervation to the GI tract

Answer 3

T5-L3 spinal nerves >through sympathetic trunk >form Greater (T5-9), lesser(T10-11) and least (T12) abdominopelvic splanchnic nerves
>synapse in Coeliac,Renal,Superior mesenteric ,Inferior mesenteric ganglia

Question 4

What does the sympathetic NS innervate in the GI tract and what is the action ?

Answer 4

Mainly blood vessels

Inhibits GI function

Question 5

Describe the parasympathetic innervation to the gut

Answer 5

Vagus nerve (CN X)
Pelvic splanchnic nerves S2,3,4

Question 6

Which vagus nerve is anterior to the stomach ?

Answer 6

Left. Due to clockwise rotation of stomach

Question 7

What is released from the postganglionic fibres of the parasympathetic innervation ?

Answer 7

Acetylcholine

Peptides :
Gastrin releasing peptide
Vaso inhibitory peptide

Question 8

What is innervated by the parasympathetic NS in the GI tract and what is the effect ?

Answer 8

Smooth muscle , endocrine and secretory structures

Stimulatory effect

Question 9

Which part of the GI tract is innervated by the vagus nerve ?

Answer 9

From oesophagus to transverse colon

Question 10

Name the two plexus of the enteric NS

Answer 10

Sumucosal (Meissner’s):in submucosa

Myenteric (Auerbach’s) : between circular and longitudinal muscle layers of the Muscularis Propria

Question 11

Briefly describe the main function of the enteric plexuses

Answer 11

Submucosal : control secretions and blood flow

Myenteric : motility

Question 12

What are enteroendocrine cells ?

Answer 12

Cells in mucosa of GI that secrete hormone

Question 13

Briefly describe the difference between gastrointestinal hormones and paracrine peptides

Answer 13

Both released from enteroendocrine cells but hormones go through portal circulation and systemic circulation to act on target , paracrine act locally by diffusion

Question 14

Give an eg of paracrine control in the GI tract

Answer 14

D cell in stomach stimulated by acid in antrum release somatostatin which inhibits nearby G cells from releasing Gastrin , Hitamine

Question 15

What are the two main categories of gastrointestinal hormones ?

Answer 15

Gastrin family : Gastrin and Cholecystokinin

Secretin Family : Secretin and Gastric inhibitory polypeptide

Question 16

CCK is produced by …

Answer 16

I cells of duodenum and jejunum

Question 17

What stimulates the secretion of CCK

Answer 17

Fat and protein

Question 18

What is the action of CCK ?

Answer 18

Gall bladder contraction
Pancreas stimulation
Relaxation of sphincter of Oddi allowing release of bile and pancreatic enzyme release in the duodenum

Question 19

Where is secretin produced ?

Answer 19

S cells of duodenum

Question 20

What stimulates the secretion of secretin ?

Answer 20

H+ and fatty acids

Question 21

What is the effect of secretin?

Answer 21

Inhibits gastric acid production

Stimulates HCO3 from pancreas and gallbladder

Question 22

Where is Gastric inhibitory polypeptide secreted ?

Answer 22

Duodenum and Jejunum

Question 23

What stimulates GIP secretion ?

Answer 23

Sugars,amino acids , fatty acids

Question 24

What is the effect of GIP ?

Answer 24

Increases insulin

Decreases gastric acid secretion

Question 25

what can cause appendicitis ?

Answer 25

Lymphoid ring around opening of appendix gets enlarged (infection ?) > block lumen > inflammation

Question 26

Briefly explain the difference between visceral and parietal peritoneum and explain why ?

Answer 26

Visceral peritoneum , pain is vague and in midline because innervation is splanchnic : sensory nerves run along sympathetic splanchnic nerves back to spinal sensory ganglia , recognise pain at the vertebral level so pain is felt at dermatomes

Parietal peritoneum comes from somatic origin so pain can be localised

Question 27

Explain why visceral pain from foregut structures is feels in the epigastric region

Answer 27

Foregut structures innervated by greater splanchnic nerve which is composed of spinal nerve T5 to T9 , dermatomes of these vertebral level are from below nipples to above umbilicus

Question 28

Which part of the GI tract has skeletal muscle ?

Answer 28

Pharynx
Upper 1/3 oesophagus
External anal sphincter

Question 29

Where in the GI tract is there Tonic contraction ?

Answer 29

Upper stomach
Ileocaecal valve
Internal anal sphincter

Question 30

Briefly explain peristalsis

Answer 30

Movement of content in one direction

Proximal contraction , distal relaxation

Question 31

Explain segmentation

Answer 31

Contraction of non adjacent segments split contents , food is moved forwards then backward

Mixes , breaks and move content

Question 32

What is mass movement ?

Answer 32

Distal colon , rapid movement of content in rectum

Question 33

Give eg of motility problem

Answer 33

Paralytic ileus
Achalasia : failure to relax LOS
Hirschsprung’s disease : no plexuses

Question 34

What is the role of stomach acid ?

Answer 34

Activates enzymes
Prepare protein for digestion
Barrier to infection

Question 35

Where is HCO3 secreted ?

Answer 35

saliva,stomach,duodenum,pancreas,liver

Question 36

Which waste products are secreted in the GI tract ?

Answer 36

Cholesterol

Bilirubin

Question 37

What is the role of bike salts ?

Answer 37

Emulsify fat :increase surface area of lipids

Question 38

How is water absorbed in the gut ?

Between, after meals and in colon

Answer 38

Between : follow absorption of Na+ , Cl-

After : with nutrients and Na (sodium co transport)

In colon : Epithelial Na Channel