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Guyton > Unit 12 > Flashcards

Unit 12 Flashcards

1
Q

What are the 2 types of electrical activity in gastrointestinal smooth muscle?

A

Slow waves
Spikes

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2
Q

Which intestinal cells act as electrical pacemakers?

A

Interstitial cells of Cajal

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3
Q

How do ion channels in GI smooth muscle differ from nerve cells?

A

Channels responsible for action potentials predominantly allow calcium ions to enter with a smaller amount of sodium - calcium-sodium channels
Slower to open and close

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4
Q

What factors can alter the resting potential of GI smooth muscle?

A

Depolarised by:
Stretch
ACh stimulation
Stimulation by GI hormones

Hyperpolarised by:
NEp and Ep
Stimulation of sympathetic nerves

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5
Q

Describe the structure of the enteric nervous system

A

Myeneteric plexus - between longitudinal and smooth muscle layers - GI movement
Submucosal plexus - in submucosa - secretions and blood supply

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6
Q

Which nerves supply the parasympathetic input to the GIT?

A

Cranial - vagus
Caudal - pelvic

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7
Q

Where is gastrin secreted?

A

G cells of stomach

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8
Q

What stimulates gastrin secretion?

A

Stomach distension
Products of protein digestion
Gastrin-releasing peptide - released during vagal stimulation

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9
Q

What are the actions of gastrin?

A

Gastric acid secretion
Gastric mucosal growth

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10
Q

Where is CCK secreted?

A

I cels of duodenum and jejunum

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11
Q

What stimulates CCK secretion?

A

Digestive products of fat

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12
Q

What action does CCK have?

A

GB contraction
Inhibits stomach contraction
Inhibits appetite

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13
Q

Where is secretin released?

A

S cells - duodenum

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14
Q

What stimulates secretin release?

A

Acidic gastric juice entering duodenum

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15
Q

What are the effects of secretin?

A

Promotes bicarbonate secretion
Mild effect on motility

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16
Q

Where is glucose-dependent insulinotropic peptide (GIP) released?

A

K cells of mucosa of upper small intestine

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17
Q

What stimulates GIP release?

A

Fatty acids and amino acids

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18
Q

What are the effects of GIP?

A

Slows gastric emptying into duodenum. Reduces secretion of gastric acid
Stimulates insulin secretion

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19
Q

Where is motion secreted?

A

M cells. Stomach and upper duodenum

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20
Q

What stimulates motion secretion?

A

Fasting

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21
Q

What is the action of motilin?

A

Stimulates interdigestive myoelectric complexes

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22
Q

Which GI hormones have a vasodilator effect?

A

CCK, VIP, gastrin, secretin

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23
Q

What 3 factors increase local GI blood flow?

A

Hormones
Kinins - kalliidn and bradykinin
Reduced oxygen concentration

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24
Q

What is the main promotor of gastric emptying?

A

Gastrin

25
Q

What neurological factors inhibit stomach emptying?

A

Enterogastric reflex
- directly to stomach through enteric nervous system
- through extrinsic nerves via pre vertebral sympathetic ganglia
- through vagus nerve to brainstem

26
Q

What factors activate the enterogastric inhibitory reflex?

A

Distension of duodenum
Irritation of duodenal mucosa
Acidity of duodenal chyme
Osmolality of the chyme
Presence of protein in chyme

27
Q

What hormone inhibits gastric emptying?

A

CCK
Secretin and GIP to lesser extent

28
Q

What hormones increase intestinal peristalsis?

A

Gastrin, CCK, insulin, motilin, serotonin

29
Q

What hormones inhibit small intestinal motility?

A

Secretin and glucagon

30
Q

What nerves are responsible for a) conscious and c) unconscious control of defecation?

A

a) Pudendal
b) Pelvic

31
Q

Are anaerobic/aerobic bacteria more common in the lower intestine?

A

Anaerobic

32
Q

What are the predominant cells in the a) body, b) fundus and c) antrum of the stomach?

A

a) Mucus neck cells, parietal cells, chief cells
b) Enterochromaffin-like cells, somatostatin-producing cells
c) Gastrin and somatostatin-producing cells

33
Q

What stimulates gastrin release?

A

Luminal peptides, digested protein, acetylcholine, gastrin-releasing peptide

34
Q

What stimulates gastric acid secretion?

A

Gastrin, histamine, acetylcholine

35
Q

What stimulates somatostatin release? How does it affect the stomach?

A

pH <3
Reduces gastrin, histamine and acid secretion

36
Q

What acid-base abnormalities are seen in combination with vomiting?

A

Metabolic acidosis - most common
Metabolic alkalosis - when gastric outflow/proximal duodenum obstructed

37
Q

In what situations is metabolic alkalosis recognised in patients with GI signs?

A

Outflow obstruction, CPV, pancreatitis, gastrinoma

38
Q

DDX elevated gastrin and low gastric pH?

A

Gastrinoma
Hepatic/renal disease

39
Q

How is gastrinoma diagnosed?

A

Elevated gastrin + low gastric pH
Gastrin measurement following secretin or Ca infusion

40
Q

How is achlorhydria diagnosed?

A

Elevated gastrin and gastric pH >3
Pentagastrin or bombesin stimulation

41
Q

What does a metabolic alkalosis, hypochloraemia, hypokalaemia and acidic urine suggest?

A

Upper GI obstruction or hypersecretory state

42
Q

Where are NSAID-related ulcers most often found?

A

Antrum

43
Q

How is gastrinoma medically managed?

A

Omeprazole + somatostatin analogue (eg octreotide)

44
Q

What is a potential treatment for large gastric ulcers?

A

Octreotide

45
Q

Metoclopramie MOA

A

Antagonises D2-dopaminergic and 5ht3-serotonergic receptors
Cholinergic effect on smooth muscle

46
Q

Ondansetron MOA

A

Peripheral 5HT3 antagonism

47
Q

Maropitant MOA

A

NK-1 antagonist

48
Q

What is the risk of maropitant in dogs <8 weeks old

A

Bone marrow hypoplasia described

49
Q

What parasites are associated with gastritis? What species do they infect?

A

Ollulanus Tricuspis - cats
Physaloptera - cats and dogs

50
Q

How is ollulanus tricuspis spread? How is it diagnosed/treated?

A

Cat to cat - ingestion of vomitus/autoinfection
Evaluation of gastric juice, vomit or histo
Fenbendazole

51
Q

What stain is used to confirm pythosis?

A

Gomori’s methenamine silver

52
Q

How does gastric pythosis present?

A

Thickening of gastric outflow tract

53
Q

How is gastric pythosis treated?

A

Aggressive resection
Itraconazole and terbinafine for 2-3 months

54
Q

In which breed has atrophic gastritis been described?

A

Lundehund

55
Q

What enzyme is responsible for the majority of carbohydrate digestion?

A

Pancreatic amylase

56
Q

Where does the majority of protein digestion occur?

A

Upper small intestine - pancreatic enzymes

57
Q

Which cranial nerves are involved in swallowing?

A

V, IX, X

58
Q
A

Guyton (10 decks)

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