7. Gut/brain Signalling

Question 1

Enteric system

1. Describe in one sentence; interesting part
2. 2 nervous pathways that interact between enteric and central nervous systems
3. ENS’s 2 main plexuses

Answer 1

1. Autonomic nerve system specifically for GI tract; peristalsis can still take place wo vagus nerve
2. Vagus and splanchnic
3. Myenteric & submucosal/Meissner’s nerve plexus

Question 2

Brain-gut axis
1. Gut to brain: name 2 nerve fibres of the 2 neural pathways & which nerve is related to each
2 Brain to gut: same as above
3 which is para/sympathetic
4 Act via/on?
5 name ganglions on the of the afferent fibres

Answer 2

1. Afferents: Vagal afferent (related to vagus)
Spinal afferent (related to splanchnic)

2. Efferents: Vagal efferent (related to vagus)
Sympathetic efferent (related to splanchnic)

3. Vagal efferent=parasympathetic (related to fullness)
   Sympathetic efferent=sympathetic

4.vagal efferent acts via enteric neurons
Sympathetic efferent act via enteric neurons
Blood vessels and skin only receive signals from sympathetic efferent

5 nodose ganglia on Vagal afferent; prevertebral gangila on splanchnic/pelvic nerve

Question 3

What do enteric neurons control

Answer 3

Gut motility/peristalsis (motor neurones), secretion, blood flow, mucosal growth

Question 4

Draw cross section of GI tract with label of each layer of tissue/cells
Include layers and plexuses
After lumen, 7 layers

Answer 4

Lumen
Epithelial lining
Mucosa w mucosal glands
Submucosa w glands and submucosal plexus
Circular muscle w myenteric plexus
Longitudinal muscle
Mesentery
Serousa

Question 5

Describe vagal reflex to food

Answer 5

Check pp

Question 6

3 classic phases of gastric acid secretion

Include name and release of xyz

Answer 6

1 CEPHALIC; Ach & gastrin releasing peptide (taste and smell release these)

2 GASTRIC; gastrin, peptide hormone

3 INTESTINAL; inhibitory factors eg ghrelin

Question 7

Role of splanchnic afferent neurones & gut derive pain (4 of them) include:
a Which splanchnic nerves
b ganglion
c Viscera 
d region of referred pain

Answer 7

1a Greater splanchnic T5-9
1b coeliac
1c Foregut
1d Epigastric

2a Lesser T10/11
2b Super mesenteric
2c Midgut
2d Periumbilical

3a Least T12
3b Aorticorenal
3c Kidneys
3d Lower thoracic

4a Lumbar L1-2
4b Inf mesenteric
4c Hind gut
4d Hypogastric

Question 8

5 examples of gut derived pain

Answer 8

1. Nociception:
   a. hyperalgesia (increased response to painful stimulus)
   b. Allodynia: painful response to stimulus that should not be painful
2. Acid-peptic related:
   a. Heartburn (acid re flux)
   b. Peptic ulcer: pain in oes, stom, duod
3. Distension:
   Mechanoreceptor detect stretch above threshold (e.g. if eat too much it hurts)
4. Inflammatory bowel disease
   (Only small intestine; inflammation sensitises spinal afferent neurons)
5. IBS (irritable bowel syndrome):
   Whole of intestine; feel bloated/swelling/distention/discomfort; constipation or diarrhoea

Question 9

Satiety definition & what it controls

Satiation definition & what it controls

Answer 9

Satiety: fullness after eating; controls time between eating occasions

Satiation: prompts termination of eating; controls amount eaten in one go

Question 10

CCK 
1 Released by cell & where
2 Stimulated/inhibited by
3 Receptor
4 acts on which part of nervous system
5 Effects of it

Answer 10

1. I cells in proximal small intestine, pancreatic acinar cells
2. Stimulated by fat, protein
   Inhibited by bile salts/acids
3. CCK1
4. Vagus, brainstem, hypothal
5. Increase satiation by
   Stimulating pancreatic enzyme secretion & gall bladder contraction (increase small intes digestion)
   Inhibit food intake and gastric emptying via vagal afferent

Question 11

GLP-1 
1 Released by cell & where
2 Stimulated/inhibited by
3 Receptor
4 acts on which part of nervous system
5 Effects of it

Answer 11

1. L cell in ileum, colon
2. Stimulated by Glucose, fat, protein
   Inhibited by somatostatin
3. GLP-1R
   4.Vagus, brainstem, hypothal
4. Increase satiation and Antietam by
   Stimulating insulin secretion
   Inhibiting food intake & gastric emptying via vagal afferent

Question 12

Ghrelin 
1 Released by cell & where
2 Stimulated/inhibited by
3 Receptor
4 acts on which part of nervous system
5 Effects of it

Answer 12

1. Gastric mucosa-corpus
2. Controlled by circadian rhythm
   Stimulated by lack of sleep, low calories
   Inhibited by macronutrients (glucose, protein, fat etc)
3. GHS-R1a (on vagal afferent & hypothal neurons)
4. Vagus, brainstem and hypothal
5. Meal initiator (highest in loop before meal); long term body weight regulator:
   Stimulates food intake and gastric emptying
   Inhibits CCK action on vagal afferent neurons