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Physiology > Gastrointestinal > Flashcards

Gastrointestinal Flashcards

0
Q

Factors that make the GI smooth muscle cell membrane more negative, making it less excitable.

A

Norepinephrine or epinephrine

Stimulation of sympathetic Nerves that secret mainly norepinephrine at their ending.

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1
Q

Factors that depolarize the GI smooth muscle cell membrane, making it more excitable.

A

Stretching of the muscle, acetylcholine (parasympathetic nerves), specific gastrointestinal hormones

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2
Q

Kinds os electrical waves in the GI system

A

Slow waves (caused by pacemakers - interstitial cells of Cajal) - do not cause the Ca++ to enter the cells, only Na - no contraction
Spikes - at peak of slow waves, Ca enter the fibers - contraction,
Tonic contractions - repetitive spike potentials, hormones or other factors

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3
Q

Enteric nervous system

A

Myenteric plexus - Auerbach (between longitudinal and circular muscle layers)
Submucosa plexus - Meissner
Parasympathetic (vagus) - cranial - mouth, pharinge, esophagus, stomach, pancreas, -sacral - sigmoid and anus
Sympathetic - inhibit intestinal tract smooth muscle, excites mucosal muscle

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4
Q

Stimuli to Gastrin secretion by G cells of the Antrum of stomach

A

Distention of stomach
Products of protein
Gastrin realizing peptide - released by nerves of mucosa during vagal stimulation.

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5
Q

Actions of Gastrin

A

Stimulation of gastric acid secretion
Stimulation of growth of gastric mucosa
Vasodilatation
Promotes stomach emptying (enhance activity of pyloric pump

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6
Q

Stimuli to secretion of cholecystokinin (CKK) by I cells in mucosa of duodenum and jejunum

A

Digestive products of fat, fatty acids and monoglycerides in the intestinal contents

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7
Q

Actions of Cholecystokinin

A

Contracts gallbladder
Relaxation of sphincter of Oddi
Secretion of pancreatic digestive enzymes by acinar cells
Inhibits stomach contraction - give time for digestion of fat
Inhibits appetite - prevent over eating during meals - stimulate sensory nerves in duodenum
Vasodilatation

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8
Q

Stimuli to secretin secretion by S cells in duodenum

A

Acid gastric juice emptying from pylorus

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9
Q

Action of secretin

A

Mild effect on GI motility
Promote pancreatic secretion of bicarbonate - neutralize acid in small intestine
Stimulates liver ducktail secretion of watery solution of Na and HCO3
Vasodilatation

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10
Q

Stimuli to secretion of Gastric inhibitory peptide by mucosa of upper small intestine

A

FA, AA and to a lesser extend, carbohydrates

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11
Q

Action of Gastric inhibitory peptide (GIP)

A

Mild effect in decreasing motor activity of stomach when usurper small intestine is already overloaded
Stimulates insulin secretion ( glucose-dependent insulinotropuc peptide.

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12
Q

Stimuli for secretion of motility by stomach and upper duodenum

A

Fasting

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13
Q

Actions of motilin

A

Increase GI motility, released cyclically and stimulates waves of GI motility called interdigestive myoelectric complexes

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14
Q

Where does the blood of portal vein comes from?

A

All the blood from gut, spleen and pancreas

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15
Q

What comes with the blood from portal vein to the liver?

A

Bacteria - removed by reticuloendothelial cells before enters vena cava
Non-fat, water-soluble nutrients absorbed from gut (CH, ptn).

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16
Q

Where do the fats absorbed fro GI tract go?

A

Absorbed into intestinal lymphatics and then conducted to systemic circulating blood by way of the thoracic duct, bypassing liver.

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17
Q

Factors that cause vasodilatation in GI tract after a meal

A

Peptide hormones: CKK, vasoactive intestinal peptide, Gastrin, secretin
Kallidin and bradykinin secreted by GI glands
Decreases oxygen concentration - increase adenosine - potent vasodilator

18
Q

Factors that control small intestine peristalsis

A

Enhances: gastroenteric reflex (Myenteric plexus), Gastrin, CCK, insulin, motilin, serotonin
Inhibits: glucagon, secretin

19
Q

Anus sphincter

A

Internal-circular smooth muscle

External - striated voluntary muscle - pudendal nerve

20
Q

Autonomic reflexes that affect bowel activity

A

Excitatory: Gastrocolic, duodenocolic, gastroileal,
Inhibitory:enterogastric, peritoneointestinal, renointestinal, vesicointestinal

21
Q

Secretion of oxyntic gastric glands (body and fundus)

A

1-mucus neck cells - mucus
2-peptic or chief cells - pepsinogen
3-parietal or oxyntic cells - hydrochloric acid and intrinsic factor

22
Q

Actions of acetylcholine, Gastrin and histamine in gastric secretion

A

Acetylcholine - stimulates secretion of pepsinogen (chief cells), HCl (parietal cells) and mucus (neck cells)
Gastrin and histamine - stimulates secretion of HCl.

23
Q

Actions of pepsinogen

A

Activated to form pepsin when in contact with HCl

Pepsin - proteolytic enzyme when in highly acid medium ( digestion of colagen)

24
Q

Intrinsic factor

A

Produced by parietal cells
Essential for absorption of vit B12 (maturation of red cells) in the ileum
Absence of intrinsic factor = pernicious anemia

25
Q

Inhibit gastric secretion:

A

Reverse enterogastric reflex
Secretin (mainly), gastric inhibitory peptide (glucose-dependent insulinotropic peptide), vasoactive intestinal polypeptide, somatostatin.

26
Q

Side effect of chronic use of proton pump inhibitor

A

Increase Gastrin secretion

27
Q

What occurs in the stomach between meals?

A

Increase of secretion of somatostatin by D cells

28
Q

The cephalic phase of HCl gastric secretion is mediated by:

A

Parasympathetic nervous activity

29
Q

Stimuli that causes pancreatic secretion

A

1) acetylcholine and cholecystokinin - secretion of pancreatic digestive enzymes
2) secretin - secretion of water solution of sodium bicarbonate

30
Q

Functions of bile salts and lecithin

A

Emulsification of fat particules - make the fat globules readily fragmentable by agitation with water
Helps absorption of FA, monoglycerides, cholesterol and other lipids - transport medium to carry these particules to brush borders of intestinal epithelial cells

31
Q

Composition of bile

A

1) Bile salts - produced from cholesterol
2) Cholesterol
3) Bilirubin- end product of hemoglobin destruction
4) Lecithin - phospholipid
5) Electrolytes

32
Q

What are Brunner’s glands?

A

Mucous glands at duodenum, between pylorus and papilla of Vater, that secrets mucus is response to: tactile or irritating stimuli, vagal stimulation and GI hormones (secretin)

33
Q

A 20 year old male develops severe diarrhea for 2 days. Will this condition alter his ventilation? If so, how?

A

Yes, increase minute ventilation

34
Q

A 20 year old male develops severe diarrhea for 2 days. Will this condition affect his acid-base status? If so, how?

A

Yes, metabolic acidosis.

35
Q

Jim had severe diarrhea for 2 days. What would be the best way to rehydrate his body?

A

drink isotonic salt solution containing sugar

36
Q

What is the dominant mechanism for entry of amino acids into the body?

A

Secondary active transport

37
Q

Na is actively transported through the intestinal membrane. What are the other substances that are dragged (co-transport) with it (secondary active absorption)?

A

1) glucose
2) amino acids
3) sodium-hydrogen exchanger

38
Q

How are chloride ions absorbed in the intestine?

A

1)By diffusion following electrical gradient created by Na absorption
2) in the ileum and large intestine by chloride-bicarbonate exchanger
Obs: chloride excites cell on basolateral membrane through chloride channels

39
Q

How bicarbonate is absorbed in duodenum and jejunum?

A

1) hydrogen ions are secreted in exchange for Na
2) hydrogen ions combine with bicarbonate ions =>H2O+CO2
3) CO2 is absorbed into the blood and expired through lungs

40
Q

What is the importance of the bacterial activity in the colon?

A

To form vitamins K, B12, thiamine, riboflavin.
Digestion of small amounts of cellulose.
Form gases

41
Q

Which hormone stimulates strong smooth muscle contractions in the stomach?

A

Motilin - initiates migrating motor complex - sweeping of GI

42
Q

What are the consequences of loss os stomach secretions in gastric atrophy?

A

Achlohydria=>pepsin is nit activated

Pernicious anemia

43
Q

Most frequent sites os peptic ulcer

A

Within a few centimeters of the pylorus
Lesser curvature o the antral end of the stomach
More rarely in the lower end of the esophagus
Marginal ulcer - wherever a surgical opening has been made between the stomach and the jejunum

Physiology (2 decks)

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