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S&F IV: Exam One > GI Physiology > Flashcards

GI Physiology Flashcards

0
Q

Vagovagal Reflex

A

Information from receptors in mucosa and smooth muscle are relayed to the CNS via Vagus afferents and a response is triggered via Vagus efferents

*Dominates control of esophagus, stomach, and defacation

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1
Q

Extrinsic Innervation of GI Tract

A

Vagus- Esophagus, stomach, SI, Upper Colon

Pelvic Nerve- Descending and sigmoid colon, rectum, anal canal

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2
Q

Enteric Nervous System

A

Consists of networks formed by the myenteric and submucosal plexuses; allows for stimulus in one part of tract to produce response in another in absence of extrinsic system

*Myenteric-controls motility
Sumucosal-controls secretion & found in intestines

*Dominates control of intestines

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3
Q

Zollinger-Ellison Syndrome

A

Hypersecretion of HCl due to presence of gastrinoma; development of ulcers, diarrhea, and steatorrhea occurs

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4
Q

Gastrin

A

Secreted by: G-cells in antrum of stomach

Action: HCl secretion

Releaser: Small peptides, AAs, gastric distension, vagal stimulation

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5
Q

CCK

A

S- I cells of duodenum and jejunum

A- Gallbladder contraction
Pancreatic enzyme secretion
Bicarbonate secretion
Inhibits gastric emptying

R-Small peptides, AAs, FAs

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6
Q

Secretin

A

S- S-cells in the duodenum

A- Bicarbonate secretion
Biliary bicarbonate production
Inhibits HCl secretion

R- Acid

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7
Q

Glucose-dependent Insulinotropic Peptide

A

“GIP”

S- K-cells in duodenum and jejunum

A- Insulin release
Inhibits HCl secretion

R- FAs, AAs, oral glucose

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8
Q

Motilin

A

S- Duodenum and jejunum

A- Stimulates gastric motility

R- Nerves (during starvation)

*Helps to clear intestines for food when it arrives

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9
Q

Somatostatin

A

S- D-cells in GI mucosa

A- Inhibits GI hormone release and HCl secretion

R- Acid

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10
Q

Vasoactive Intestinal Peptide

A

“VIP”

S- GI Mucosa and smooth muscle

A- Relaxes GI smooth muscle
Stimulates pancreatic and intestinal secretion

R-?

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11
Q

Histamine

A

S- ECL cells

A- Stimulates HCl secretion

R- Gastrin

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12
Q

Gastrin-releasing peptide

A

S- Gastric mucosa

A- Gastrin release

R- Vagal stimulation

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13
Q

Enkephalins

A

S- GI mucosa and smooth muscle

A- Stimulates contraction of smooth muscle
Inhibits intestinal secretions

*Is why opiates are useful in treating diarrhea

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14
Q

Slow Waves

A

Rhythmic changes in the potential of gastric smooth muscle cells, & if the plateau phase exceeds threshold, contraction will occur; the frequency of these waves determines the maximum frequency of contractions

  • Neural and hormonal input can produce bigger contractions and inhibit APs
  • Only place where an AP MIGHT occur is the stomach
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15
Q

Greatest contribution to salivation

A

Submaxillary Gland

16
Q

Acinus

A

Blind end of a duct that secretes the initial saliva

17
Q

Flow of saliva

A

Acinus => Intercalated duct => Striated duct => Intralobular duct => Interlobular duct

18
Q

Myoepithelial cells

A

Contraction of these cells ejects saliva into the mouth

19
Q

Control of salivation

A

Primarily under parasympathetic control; sectioning of these nerves cause the gland to atrophy

*Some sympathetic fxn (constriction of blood vessels and contraction of myoepithelial cells)

20
Q

Modification of saliva

A

Initially reabsorb Cl- and secrete HCO3-; later reabsorb Na+ and secrete K+ and HCO3-

21
Q

Effects of increased saliva flow on ionic composition

A

Na- Increased

Cl- Increased

K- Initial decrease, then plateaus

HCO3- Initial increase, then plateaus

*Due to the activity of the pumps related to these ions

22
Q

Xerstomia

A

Commonly caused by anti-depressants or Sjögren’s syndrome, this is the term for a lack of salivary secretion

*Pts. will have dental caries and chronic mouth infxns; treat w/ frequent water consumption or pilocarpine mouthwashes (cholinergic agonist)

23
Q

Deglutition

A

Swallowing initiated by voluntary action of collecting a bolus of food; nasopharynx gets closed off by soft palate, layngeal muscles close glottis and elevate larynx, and peristalsis begins in the pharynx to push the bolus thru the relaxed UES

24
Q

Control of deglutition

A

Reflex is controlled in the swallowing center in the medulla; can be initiated voluntarily but requires something to trigger swallowing reflex

25
Q

Structure of esophagus

A

Upper 1/3=striated muscle

Lower 1/2= smooth muscle

26
Q

UES

A

Separates esophagus from oral cavity and prevents entry of air; formed by the cricopharyngeal muscle

27
Q

LES

A

Separates esophagus from stomach and prevents entry of gastric acid; has increased pressure

28
Q

Primary peristaltic contraction

A

Begins after swallowing; food pushed to relaxed LES and enters stomach

29
Q

Secondary Peristaltic Contraction

A

Initiated by presence of food in the esophagus that stretches mechanoreceptors; continues until all material removed

30
Q

GERD

A

Decreased tone of LES causes a reflux of stomach acid

*Severe heart burn, ulcers, and esophagitis

Treated w/ medications, lifestyle changes

31
Q

Hiatal Hernia

A

LES and stomach moved up => weakened acid reflux barrier

32
Q

Barrett’s Esophagus

A

Constant injury due to gastric acid leads to metaplasia and possibly esophageal cancer

33
Q

Achalasia

A

Neuromuscular disorder of lower 2/3 of esophagus leading to absence of peristalsis and failure of LES to relax

*Dysphagia, regurgitation, weight loss

34
Q

Interstitial cells of Cajal

A

Produce slow waves in GI cells; occurs due to influx/efflux of Ca and are not affected by hormonal input

35
Q

Lesion in Swallowing Center

A

Found in the medulla; causes loss of pharyngeal phase of swallowing

S&F IV: Exam One (20 decks)

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