Regulstion of gut

Question 1

What is the enteric nervous system?

Answer 1

Intrinsic nervous system

• wall of the GI tract contains millions of neurons
• independently controls GI
  
  • integrates motor and secretory activities of GI

Question 2

What might arise as a result of enteric dysfunction?

What might cause it?

Answer 2

Inflammation

Irritable bowel syndrome

Post-operative injury

Ageing

Question 3

What does the enteric nervous system regulate?

Answer 3

Motility

Blood flow

Water and electrolyte transport

Secretion

Absorption

Question 4

Which neurons are used?

Answer 4

Standard

• Sensory
• Motor
• Interneurons
  
  • Decides magnitude of stimulus - not just a refluex

Question 5

Where are the main nerve plexuses located?

Answer 5

Cuts through layers

• Myenteric plexus
  
  • between longitudinal and circular muscle
    
    • for gut motor function
• Submucosal plexus
  
  • underneath epithelia
    
    • for epithelial, blood flow and endocrine function
• Deep muscular plexus
  
  • in the circular muscle

Question 6

What does the autonomic nervous system regulate?

Answer 6

Smooth muscle, cardiac muscle and glands

Question 7

How are the foregut and midgut sympathetically innervated?

Answer 7

Thoracic splanchnic nerves

Question 8

How is the hindgut sympathetically innervated?

Answer 8

Lumbar splanchnic nerves

Question 9

What is the point of sympathetic nerve activation?

Answer 9

Inhibit GI system activity

Question 10

How are the foregut and midgut parasympathetically innervated?

Answer 10

Cranial nerves

Question 11

How is the hindgut sympathetically innervated?

Answer 11

Pelvic nerves

Question 12

What are the main autonomic neurotransmitters?

Answer 12

NA - symp

ACh - para

Question 13

How does the autonomic nervous system interact with the GI?

Answer 13

Synapses to myenteric plexuses via enteric system

Question 14

What is the point of parasympathetic nerve activation?

Answer 14

Stimulate GI activity

Question 15

WHat is intramural plexus?

Answer 15

Intramural plexus

- plexus found in ENS

Question 16

What is intrinsic and extrinsic innervation of GI?

Answer 16

Intrinsically?
- neurons of the ENS

Extrinsically

• afferent - pain, nausea
• efferent - coordination of para and symp

Question 17

The nerve fibres of the PNS and SNS are long or short? - pre synapse and post

Answer 17

PNS

• LONG PREGANGLIONIC
• SHORT POSTGANGLIONIC

SNS

• SHORT PREGANGLIONIC
• LONG POSTGANGLIONIC

Question 18

What is the function of the GI endocrine system?

Answer 18

Not necessarily endocrine organ but contains endocrine cells that can produce hormones

Hormone production which can act as neurocrine or paracrine factors
- released by nuclei

Regulation of the mechanical, chemical and enzymatic processes of digestion

Question 19

How might hormones be released?

Answer 19

Apical membrane of cell has sensors that check contents of gut lumen and then allow stimulation of hormone release from basal.

Question 20

Which hormones do L-cells secrete?

Answer 20

GLP-1 - glucagon like peptide

- satiety

Question 21

What is GLP-2 required for?

Answer 21

Growth and development of GI tract

Question 22

Give an example of paracrine action within the GI system

Answer 22

Histamine released form stomach wall cells is s key stimulus for HCl secretion by parietal cells

Question 23

What is the function of gastrin? What stimulates and inhibits it?

Answer 23

Stimulates gastric acid release

• stimulated by
  
  • AA and peptides ins tomach
  • Gastric distension
  • Vagus nerve
• inhibited by
  
  • fall of stomach pH to below 3

Question 24

Function of somatostatin and

Answer 24

Synthesised in D cells of gastric duodenal mucosa

Stimulated by
- mixed meal entry

Inhibits

• gastric secretion
• motility
• hormone release
• growth and proliferation

Question 25

Why is an analogue used instead of somatostatin? | What is somatostatin used for?

Answer 25

Neuroendocrine tumours - longer half life - longer effect -

Question 26

Function of secretin and where made?

Answer 26

S cells of upper duodenum Stimulus - pH drop Causes - bicarbonate secretion by pancreas - inhibits gastric acid and emptying

Question 27

Function of CCK and where?

Answer 27

Cells in the small intestine Stimulated by - fat and peptides in upper small intestine Independent of vagus stimulates - pancreatic enzyme release - delays gastric emptying - gallbladder contraction - decreases food intake

Question 28

GIP function and made>

Answer 28

Mucosal K cells Made when meal ingested Stimulates insulin secretion and antagonists cause lower insulin release

Question 29

PYY function and where made?

Answer 29

Made in ileum - released from L cells Reduces intestinal motility, gallbladder contraction exocrine secretion of pancreas Inhibits intestinal fluid and electrolyte secretion AND food intake