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NUT1005 > Neural And Endocrine Regulation of the Digestive Tract > Flashcards

Neural And Endocrine Regulation of the Digestive Tract Flashcards

1
Q

What is the enteric nervous system

A

‘Mini brain’ of GI tract (from lower oesophagus to anus) that is a complete neural circuit modulated by the CNS via the autonomic NS

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2
Q

What is the function of the enteric nervous system

A

Controls motor and secretory functions in the GI tract

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3
Q

What are the two layers of the enteric NS

A

The myentric plexus and the submucosal plexus

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4
Q

What is the myentric plexus

A

Part of enteric NS that controls motility in the GI tract through interaction with the vagus nerve

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5
Q

What is the submucosal plexus

A

Component of enteric NS that controls the muscosa (secretion and blood flow) in the GI tract

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6
Q

What neurones make up the ENS

A

excitatory and inhibitory interneurones, secretomotorneurones and sensory neurones

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7
Q

What are the function of interneurones

A

Integrate information and initiate a response
Excitatory response- acetylcholine and substance P to promote our GI activity
Inhibitory- serotonin/5-HT, noradrenaline and enkephalins to inhibit GI activity

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8
Q

What are the function of the sensory neurones (afferent)

A

Sense mechanical, chemical and thermal changes

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9
Q

What are the functions of secretomotor neurones (efferent)

A

Motility of smooth muscle and secretion (epithelial, endocrine and vascular)
Excitatory- acetylcholine and substance P
Inhibitory- VIP, nitric oxide (NO) and adenosine triphosphate (ATP)

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10
Q

What is gastric acid secreted by

A

Parietal cells

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11
Q

Where is parietal cells located

A

Corpus of stomach

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12
Q

What are the three phases of gastric secretion

A

Cephalic, gastric and intestinal

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13
Q

What is the cephalic stage

A

Smell, sight, taste, thought and swallowing of food stimulates acid secretion via the vagus nerve ans Ach release

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14
Q

What is the gastric phase of acid secretion

A

Food entering the stomach stimulates acid secretion by distension initiating vago-vagl and ENS reflexs and Ach release, partially digested protein stimulates G cells and gastric release and low intra gastric pH inhibition via D cells and stomatostain release

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15
Q

What is the intestinal phase

A

The presence of amino acids and peptides in the small intestine stimulate acid secretion via G cells and gastric release and inhibition via enterigastrone release from endocrine cells

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16
Q

How is gastric acid secretion controlled

A

Stimulates or inhibited through direct and indirect effects of parietal cells

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17
Q

What are the 4 stimulators of acid secretion

A

Gastrin, histamine, acetylcholine and gastrin releasing peptide

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18
Q

What secretes gastrin

A

G cells

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19
Q

What secretes histamine

A

Enterochromaffin like cells

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20
Q

What secretes Ach

A

Nervous system

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21
Q

What are inhibitors of acid secretion

A

Stomatostain, cholecystokinin and secretin

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22
Q

What secretes stomatostain

A

D cells

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23
Q

What ENS response increases Cl- secretion in intestines

A

Secretagogues (Ach, serotonin/5-HT and VIP)

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24
Q

What ENS response increases NaCl absorption in intestines

A

Enkephalins and norepinephrine

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25
What is the local reflex response to intestinal distension
5-HT (serotonin) is released in response to distension od the intestinal wall which causes increased fluid and electrolyte secretion
26
What endocrine responses increase Na+ absorption in intestines
Angiotensin II and aldosterone secretion
27
What emdocrine response stimulates Cl- secretion in intestines
Guanylin secretion
28
What are the two types of Interstitial cells of Cajal (ICC)
Intramuscular ICC (ICC-IM) and ICC located alongside myenteric plexus (ICC-MY)
29
What is the function of Intramuscular ICC
Act as mediators of neurotransmission
30
What is the function of ICC-MY
Intrinsic pacemaker of GI tract by generating slow waves os electrical activity spreads to muscles
31
What 2 things is action potentials in muscle dependent om
Neurotransmitter and normal excitation to breach threshold
32
What happens in the small intestine during a fasted state
A cyclical pattern of motility is produced by the ENS, governed by the migrating myoelectric complex (MMC) in 4 phases so that peristaltic waves allow large, undigested material to pass through the tract
33
What are the 4 stages of MMC in a fasting state in the small intestine
- prolonged quiescent period - period of increasing action potentials - period of maximal APs and contractions - declining action potentials
34
What suppresses MMC in the small intestine
Feeding through vago-vagal reflexes and GI hormones (gastrin, secretin and cholecystokinin)
35
Describe segmentation (muscular activity to break down food) in the fed state
- predominant form of motility when in fed state -non propulsive - contraction of smooth muscle -churning of luminal comctents - reduces unstirred layer
36
Describe peristalsis (muscle contraction to move food) in the small intestine in a fed state
-propulsive (movement in specific direction) - sequential contraction of smooth muscle - promotes caudal movement of intestinal content to distal site for further absorption or stool elimination
37
Describe churning in the large intestine
- non propulsive - predominant motility in the colon - haustration (segmentation) - prolonged exposure for absorption
38
Describe mass peristalsis in the large intestine
- propulsive - sequential haustration - mass movement towards rectum 1-3 times per day
39
Describe ENS control of defecation
Presence of food in the stomach is sensed by mechanoreceptors leading to activation of the gastric-colic reflex (stimulates colon)
40
Describe autonomic control of defecation
Presence of chyme in the duodenum stimulates CCK, gastrin and Vagal reflex and activation of the duodenum-colic reflex (stimulates colon)
41
Describe conscious control of defecation
Voluntary defecation can be initiated by relaxing of the external sphincter and contraction of abdominal muscles
42
What are the 3 types of impaired defecation
Psychological (voluntary withholding), congenital disorders and Acquired
43
What is the intestinal break
A mechanism that controls gastric emptying
44
What inhibits gastric emptying
Stomach contents entering the small intestine (the intestinal break)
45
What controls gastric emptying
Release of intestinal hormones e.g CCK and entero-gastric neural reflexes (ENS and vagus)
46
How does the hypothalamus regulates short term appetite
Ghrelin secretion
47
How does the hypothalamus inhibit appetite in the short term
In response to food in GI tract/ absorbed nutrients CCK, glucagon-like peptide-1 and peptide YY are secreted
48
How does the hypothalamus regulate appetite in the long term
Secretion of insulin to inhibit appetite and leptin stimulate saiety
49
How is leptin secreted
Released from adipose tissue in proportion to amount of fat stored
50
What secretes CCK
I cells in the ENS
51
What is the stimulators of CCK secretion
Fatty acids and AA in duodenum, vagal Ach and CCK releasing protein
52
What inhibits CCK
Stomatostatin
53
What does CCK do
Stimulates production of bile and digestive enzyme secretions Stimulates contraction Suppresses hunger and inhibition of gastric emptying
54
Where is gastrin secreted from
G cells in the stomach
55
What stimulates gastrin secretions
Stomach distension, vagal gastrin-releasing peptide, amino acids in the stomach
56
What inhibits gastrin secretion
Acid in the stomach Stomatostain Gastric-inhibitory peptide Vasoactive intestinal peptide
57
What is the action of of gastrin
Stimulates gastric acid and pepsinogen secretion and histamine release Stimulates contraction of stomach and relaxation of pyloric sphincter (increased gastric emptying)
58
Where is secretin secreted from
S cells in the small intestine
59
What stimulates secretin release
Acid in duodenum, products of protein digestion in upper small intestine
60
What is the function of secretin
Stimulates HCO3- and fluid secretion and insulin release Inhibits gastric acid secretion
61
Where is stomatostain secreted from
D cells in the stomach/duodenum
62
What stimulates stomatostain release
Presence of acid in the stomach and small intestine
63
What inhibits stomatostain release
Vagal Ach
64
What is the function of stomatostain
Inhibits parietal cell acid secretion, release of gastrin and histamine, gastric emptying, release of insulin and glucagon , smooth muscle contraction and blood flow and exocrine secretion Stimulates fluid absorption and inhibits secretion
65
Where is glucagon-like peptide secreted from
L cells in the intestines
66
What stimulates the release of glucagon-like peptide
Presence of nutrients in intestines
67
What is the function of glucagon-like peptide
Stimulates glucose dependent insulin secretion, promotes saiety, inhibits gastric motility and emptying and inhibits gastric acid secretion
68
Where is ghrelin secreted
Ghrelin cells in stomach and duodenum
69
What stimulates Ghrelin secretion
Decreased food intake
70
What is the function of Ghrelin
Stimulates appetite and increased fat mass Activates the cholineegic-dopaminergic reward link (rewarding food intake)
71
Where is gastric inhibitory polypeptide
K cells in the small intestine
72
What stimulates gastric inhibitory polypeptide
Oral food intake
73
What is the function of gastric inhibitory polypeptide
Stimulates insulin and glucagon release, inhibits pancreatic beta cells apoptosis, regulation of appetite and saiety, inhibits gastric acid secretion

NUT1005 (17 decks)

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