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

Flashcards in GI Physiology Deck (36):
0

Extrinsic Innervation of GI Tract

Vagus- Esophagus, stomach, SI, Upper Colon

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

1

Vagovagal Reflex

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

2

Enteric Nervous System

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

3

Zollinger-Ellison Syndrome

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

4

Gastrin

Secreted by: G-cells in antrum of stomach

Action: HCl secretion

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

5

CCK

S- I cells of duodenum and jejunum

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

R-Small peptides, AAs, FAs

6

Secretin

S- S-cells in the duodenum

A- Bicarbonate secretion
Biliary bicarbonate production
Inhibits HCl secretion

R- Acid

7

Glucose-dependent Insulinotropic Peptide

"GIP"

S- K-cells in duodenum and jejunum

A- Insulin release
Inhibits HCl secretion

R- FAs, AAs, oral glucose

8

Motilin

S- Duodenum and jejunum

A- Stimulates gastric motility

R- Nerves (during starvation)

*Helps to clear intestines for food when it arrives

9

Somatostatin

S- D-cells in GI mucosa

A- Inhibits GI hormone release and HCl secretion

R- Acid

10

Vasoactive Intestinal Peptide

"VIP"

S- GI Mucosa and smooth muscle

A- Relaxes GI smooth muscle
Stimulates pancreatic and intestinal secretion

R-?

11

Histamine

S- ECL cells

A- Stimulates HCl secretion

R- Gastrin

12

Gastrin-releasing peptide

S- Gastric mucosa

A- Gastrin release

R- Vagal stimulation

13

Enkephalins

S- GI mucosa and smooth muscle

A- Stimulates contraction of smooth muscle
Inhibits intestinal secretions

*Is why opiates are useful in treating diarrhea

14

Slow Waves

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

15

Greatest contribution to salivation

Submaxillary Gland

16

Acinus

Blind end of a duct that secretes the initial saliva

17

Flow of saliva

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

18

Myoepithelial cells

Contraction of these cells ejects saliva into the mouth

19

Control of salivation

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

Modification of saliva

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

21

Effects of increased saliva flow on ionic composition

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

Xerstomia

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

Deglutition

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

Control of deglutition

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

25

Structure of esophagus

Upper 1/3=striated muscle

Lower 1/2= smooth muscle

26

UES

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

27

LES

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

28

Primary peristaltic contraction

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

29

Secondary Peristaltic Contraction

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

30

GERD

Decreased tone of LES causes a reflux of stomach acid

*Severe heart burn, ulcers, and esophagitis

Treated w/ medications, lifestyle changes

31

Hiatal Hernia

LES and stomach moved up => weakened acid reflux barrier

32

Barrett's Esophagus

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

33

Achalasia

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

*Dysphagia, regurgitation, weight loss

34

Interstitial cells of Cajal

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

35

Lesion in Swallowing Center

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