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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 pro,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
Q

What is the local reflex response to intestinal distension

A

5-HT (serotonin) is released in response to distension od the intestinal wall which causes increased fluid and electrolyte secretion

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26
Q

What endocrine responses increase Na+ absorption in intestines

A

Angiotensin II and aldosterone secretion

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27
Q

What emdocrine response stimulates Cl- secretion in intestines

A

Guanylin secretion

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28
Q

What are the two types of Interstitial cells of Cajal (ICC)

A

Intramuscular ICC (ICC-IM) and ICC located alongside myenteric plexus (ICC-MY)

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29
Q

What is the function of Intramuscular ICC

A

Act as mediators of neurotransmission

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30
Q

What is the function of ICC-MY

A

Intrinsic pacemaker of GI tract by generating slow waves os electrical activity spreads to muscles

31
Q

What 2 things is action potentials in muscle dependent om

A

Neurotransmitter and normal excitation to breach threshold

32
Q

What happens in the small intestine during a fasted state

A

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
Q

What are the 4 stages of MMC in a fasting state in the small intestine

A
  • prolonged quiescent period
  • period of increasing action potentials
  • period of maximal APs and contractions
  • declining action potentials
34
Q

What suppresses MMC in the small intestine

A

Feeding through vago-vagal reflexes and GI hormones (gastrin, secretin and cholecystokinin)

35
Q

Describe segmentation (muscular activity to break down food) in the fed state

A
  • predominant form of motility when in fed state
    -non propulsive
  • contraction of smooth muscle
    -churning of luminal comctents
  • reduces unstirred layer
36
Q

Describe peristalsis (muscle contraction to move food) in the small intestine in a fed state

A

-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
Q

Describe churning in the large intestine

A
  • non propulsive
  • predominant motility in the colon
  • haustration (segmentation)
  • prolonged exposure for absorption
38
Q

Describe mass peristalsis in the large intestine

A
  • propulsive
  • sequential haustration
  • mass movement towards rectum 1-3 times per day
39
Q

Describe ENS control of defecation

A

Presence of food in the stomach is sensed by mechanoreceptors leading to activation of the gastric-colic reflex (stimulates colon)

40
Q

Describe autonomic control of defecation

A

Presence of chyme in the duodenum stimulates CCK, gastrin and Vagal reflex and activation of the duodenum-colic reflex (stimulates colon)

41
Q

Describe conscious control of defecation

A

Voluntary defecation can be initiated by relaxing of the external sphincter and contraction of abdominal muscles

42
Q

What are the 3 types of impaired defecation

A

Psychological (voluntary withholding), congenital disorders and Acquired

43
Q

What is the intestinal break

A

A mechanism that controls gastric emptying

44
Q

What inhibits gastric emptying

A

Stomach contents entering the small intestine (the intestinal break)

45
Q

What controls gastric emptying

A

Release of intestinal hormones e.g CCK and entero-gastric neural reflexes (ENS and vagus)

46
Q

How does the hypothalamus regulates short term appetite

A

Ghrelin secretion

47
Q

How does the hypothalamus inhibit appetite in the short term

A

In response to food in GI tract/ absorbed nutrients CCK, glucagon-like peptide-1 and peptide YY are secreted

48
Q

How does the hypothalamus regulate appetite in the long term

A

Secretion of insulin to inhibit appetite and leptin stimulate saiety

49
Q

How is leptin secreted

A

Released from adipose tissue in proportion to amount of fat stored

50
Q

What secretes CCK

A

I cells in the ENS

51
Q

What is the stimulators of CCK secretion

A

Fatty acids and AA in duodenum, vagal Ach and CCK releasing protein

52
Q

What inhibits CCK

A

Stomatostatin

53
Q

What does CCK do

A

Stimulates production of bile and digestive enzyme secretions
Stimulates contraction
Suppresses hunger and inhibition of gastric emptying

54
Q

Where is gastrin secreted from

A

G cells in the stomach

55
Q

What stimulates gastrin secretions

A

Stomach distension, vagal gastrin-releasing peptide, amino acids in the stomach

56
Q

What inhibits gastrin secretion

A

Acid in the stomach
Stomatostain
Gastric-inhibitory peptide
Vasoactive intestinal peptide

57
Q

What is the action of of gastrin

A

Stimulates gastric acid and pepsinogen secretion and histamine release
Stimulates contraction of stomach and relaxation of pyloric sphincter (increased gastric emptying)

58
Q

Where is secretin secreted from

A

S cells in the small intestine

59
Q

What stimulates secretin release

A

Acid in duodenum, products of protein digestion in upper small intestine

60
Q

What is the function of secretin

A

Stimulates HCO3- and fluid secretion and insulin release
Inhibits gastric acid secretion

61
Q

Where is stomatostain secreted from

A

D cells in the stomach/duodenum

62
Q

What stimulates stomatostain release

A

Presence of acid in the stomach and small intestine

63
Q

What inhibits stomatostain release

A

Vagal Ach

64
Q

What is the function of stomatostain

A

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
Q

Where is glucagon-like peptide secreted from

A

L cells in the intestines

66
Q

What stimulates the release of glucagon-like peptide

A

Presence of nutrients in intestines

67
Q

What is the function of glucagon-like peptide

A

Stimulates glucose dependent insulin secretion, promotes saiety, inhibits gastric motility and emptying and inhibits gastric acid secretion

68
Q

Where is ghrelin secreted

A

Ghrelin cells in stomach and duodenum

69
Q

What stimulates Ghrelin secretion

A

Decreased food intake

70
Q

What is the function of Ghrelin

A

Stimulates appetite and increased fat mass
Activates the cholineegic-dopaminergic reward link (rewarding food intake)

71
Q

Where is gastric inhibitory polypeptide

A

K cells in the small intestine

72
Q

What stimulates gastric inhibitory polypeptide

A

Oral food intake

73
Q

What is the function of gastric inhibitory polypeptide

A

Stimulates insulin and glucagon release, inhibits pancreatic beta cells apoptosis, regulation of appetite and saiety, inhibits gastric acid secretion

NUT1005 (18 decks)

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