Regulation of gut function

Question 1

What sympathetic ganglion supplies the stomach?

Answer 1

Ceoliac ganglion

T6-9

Question 2

What sympathetic ganglion supplies the small intestine?

Answer 2

Superior mesenteric ganglion

Question 3

What sympathetic ganglion supplies the colon?

Answer 3

Inferior mesenteric and pelvic ganglion

L2-5

Question 4

What Neurotransmitter is used for the sympathetic nervous system supplying the gut?

Answer 4

Norepinephrine / Noradrenaline

Question 5

What does the activation of the sympathetic nervous system inhibit?

Answer 5

Activities of the gastrointestinal tract

Question 6

What nerve supplies the parasympathetic innervation to the stomach, small intestine and proximal colon?

Answer 6

Vagus nerve

Question 7

Preganglionic neurones orginate in x within the brainstem from sacral spinal cord?

Answer 7

x - dorsal vagal complex

Question 8

What neurotransmitter is used for parasympathetic innervation to gut?

Answer 8

Acetylcholine

Question 9

Activation of parasympathetic nervous system x the gastrointestinal tract.

Answer 9

x- stimulates

Question 10

What are the characteristics of the enteric nervous system?

Answer 10

• Autonomous
• Can also interact with sympathetic and parasympathetic nervous system
• The wall of the gastrointestinal tract contains many neurons – 2nd only to the brain

Question 11

What are the myenteric and submucosal plexus?

Answer 11

Plexus : network of intersecting nerves

Myenteric is the outer plexus, lies between the circular muscle and longitudinal muscle

Submucosal is the inner plexus and lies between the mucosa and muscles

Found in the walls of the gut

Question 12

What is the function of the myentreric plexus?

Answer 12

Myenteric (Auerbach’s) plexus :

controls activity of
- muscularis propria

• controls gut motor (motility) function
• tone, velocity of contraction and intensity of contraction.

Question 13

What is the function of submucosal plexus?

Answer 13

senses the local environment (gut lumen)

controls secretion, blood flow, epithelial and endocrine cell function

Question 14

How does the enteric system control the peristaltic local reflex?

Answer 14

Food enters and stretches smooth muscles –>

stimulates sensory neurones in myentric plexus = peristaltic wave ( Sequential contraction/relaxation of circular and longitudinal muscle by inhibitory/excitatory neurotransmitter cause peristalsis, which allows food to move along the GI tract )

• chemicals in food stimulate sensory nuerones –>

submucosal plexus, increase blood flow and secretion

Question 15

What does the sympathethic nervous system do to digestion? - ( 4 )

Answer 15

reduces peristalsis
reduces absorption
reduces secretion
reduces blood flow (via enteric nervous system and also directly)

Question 16

What does the parasympathethic nervous system do to digestion? - ( 4 )

Answer 16

increases peristalsis
increases absorption
increases secretion
increases blood flow

• although the gut can work without the para/sympathetic system these can enhance digestion

Question 17

What are the characteristics of Hirschsprung’s disease?

Answer 17

Most common cause of neonatal bowel obstruction

• Congenital absence of ganglion of myenteric and submucosal ( enlarged colon )

Effect:

Tonal contraction without reciprocal relaxation

Intestinal distension proximal to aganglionic segment of bowel

Treatment :

Most will require surgery

Question 18

What Endocrine hormones are involved in gut regulation?

Answer 18

gastrin, cholecystokinin, secretin, glucose-dependent insulinotropic peptide (GIP), motilin

Question 19

What Paracrine hormones are involved in gut regulation?

Answer 19

somatostatin and histamine

hormones with both endocrine and paracrine mechanisms: glucagon-like peptide-1 (GLP-1), pancreatic polypeptide, and peptide YY

Question 20

What Neurocrine hormones are involved in gut regulation?

Answer 20

secreted by postganglionic non-cholinergic neurons of the enteric nervous system
hormone that affects ‘nerves’
vasoactive intestinal peptide (VIP), gastrin release peptide (GRP), and enkephalins

Question 21

Where are enteroendocrine cells found? ( release hormones )

Answer 21

specialised epithelial cells located at the base of intestinal crypts throughout the GI tract, from stomach to colon

Question 22

What stimuli cause enteroendocrine cells to release their hormones from their granules?

Answer 22

these stimuli include small peptides, amino acids, fatty acids, oral glucose, distension of an organ, and vagal stimulation

Question 23

What stimulates Gastrin release?

Answer 23

amino acids and peptides in the lumen of the stomach
gastric distension
vagus nerve

Question 24

What hormones are secreted by duodenum?

Answer 24

Secretin

CCK

Somatostatin

Question 25

What hormones are secreted by Pancreas?

Answer 25

Insulin Glucagon Somatostatin Pancreatic polypeptide

Question 26

What hormones are secreted by stomach?

Answer 26

Gastrin Ghrelin Somatostatin Histamine

Question 27

What hormones are secreted by the small bowel?

Answer 27

Peptide YY Gastric inhibtory peptide GLP-1 GLP-2 Oxyntomodulin Neurotensin Somatostatin

Question 28

What hormones are secreted by colon?

Answer 28

PYY GLP-1 Oxyntomodulin Neurotensin Somatostatin

Question 29

What affect does Gastrin have on digestion?

Answer 29

Stimulates gastric acid by parietal cells Trophic effect on mucosa of small intestine, colon and stomach - causing them to growth gastrin release is stopped when pH falls below 3

Question 30

Where is Secretin secreted from? When?

Answer 30

Secreted by the S cells of the upper duodenum and jejunum Major stimulus is the presence of acid in the duodenum (pH falls below

Question 31

Functions of Secretin?

Answer 31

- stimulates pancreatic bicarbonate secretion (effect potentiated by CCK) - inhibition of gastric acid and gastric emptying - inhibits gastrin, acid secretion, and growth of stomach mucosa - stimulates biliary secretion of bicarbonate and fluid trophic effect on the exocrine pancreas

Question 32

Where is Cholecystokinin secreted from and when?

Answer 32

Secreted by cells most densely located in the small intestine Release stimulated by fat and peptides in the upper small intestine

Question 33

What are the functions of CCK?

Answer 33

- stimulates pancreatic enzyme release (lipase, amylase, proteases) - stimulates gallbladder contraction and relaxation of the sphincter of Oddi - delays gastric emptying - decreases food intake and meal size trophic effects on the exocrine pancreas and gallbladder

Question 34

Where does Glucose-dependent insulinotropic peptide (GIP) get secreted from?

Answer 34

Secreted by mucosal K cells (predominant in the duodenum and jejunum) GIP released following ingestion of a mixed meal Likely stimulated by change in intraluminal osmolarity

Question 35

What is special about GIP?

Answer 35

The only hormone with a response to all 3 macronutrient types (glucose, amino acid, fatty acids)

Question 36

What does GIP do?

Answer 36

Stimulates insulin secretion

Question 37

What does Motilin do?

Answer 37

Increases gastrointestinal motility

Question 38

Where is Somatostatin synthesised and released?

Answer 38

Synthesized in endocrine D cells of the gastric and duodenal mucosa, pancreas Somatostatin is a universal inhibitor (Endocrine Cyanide) Release in response to a mixed meal

Question 39

What does somatostatin inhibit?

Answer 39

``` Inhibition of gastric secretion motility intestinal and pancreatic secretions release of gut hormones intestinal nutrient and electrolyte transport growth and proliferation ```

Question 40

Where is GLP 1 produed?

Answer 40

Produced in the small intestine and secreted from L cells Release stimulated by the presence of hexose and fat

Question 41

What are the functions of GLP 1?

Answer 41

Induces satiety Increases sensitivity of pancreatic beta-cells to glucose

Question 42

where is pancreatic polypeptide released and when?

Answer 42

Secreted by PP cells in the pancreas Secretion stimulated by fat Potential role in satiety

Question 43

Where is Peptide YY secreted from and when?

Answer 43

Secreted from cells found throughout the mucosa of the terminal ileum, colon and rectum Released from L cells post- prandially (particularly protein)

Question 44

What does PYY do?

Answer 44

Reduces intestinal motility, gallbladder contraction and pancreatic exocrine secretion

Question 45

Where are neurocine hormones located?

Answer 45

Located within nerves in the gut | VIP, GRP, Enkephalins

Question 46

What does VIP do?

Answer 46

Vasoactive intestinal peptide (VIP) → relaxation of gut smooth muscle

Question 47

What does GRP do?

Answer 47

Gastrin releasing peptide (GRP) → induces gastrin release

Question 48

What do Enkephalins do?

Answer 48

Enkephalins → increase smooth muscle tone 0 inhibit peristalisis, work on opoiod receptors

Question 49

What are Neuroendocrine tumours?

Answer 49

Tumours of the neuroendocrine cells (which are found predominantly in the gastrointestinal tract and pancreas)

Question 50

What are the characteristics of Zollinger Ellison Syndrome?

Answer 50

tumour of gastric cells causing overproduction of gastrin and acid resulting in stomach and intestinal ulceration - treatment with proton pump inhibitor to inhibit acid secretion - role for somatostatin analogues to halt tumour growth and reduce secretion

Question 51

What controls the Cephalic phase?

Answer 51

Vagus

Question 52

What controls the Gastric phase

Answer 52

Local nervous system - secretion Vagal reflexes gastrin-histamine stimulation

Question 53

What controls the Intestinal phase?

Answer 53

Nervous mechanisms | Hormonal mechanisms